# Aa battery voltage percentage. Aa battery voltage percentage

## Disposable Vs. Rechargeable Batteries – In Charge

Most of our gadgets today rely on some sort of battery. But how do you power them if the grid’s down? And even if there’s electricity, how do you know you’re charging them correctly? Proper charging and maintenance is key to assuring your rechargeable batteries maintain a long and useful lifespan.

So, we’re taking an in-depth look at some of today’s most popular battery types, including an analysis of shelf life, capacity, charging methods, and the best uses suited to each type.

All rechargeable batteries are rated for capacity (C) and nominal voltage (V). Their capacity is usually measured in amp hours (Ah) in larger batteries, such as lead acid types, or in milliamp hours (mAh) for smaller cells. Capacity is defined by the battery’s ability to supply the specified current for one hour of time. For example, a battery with a rating of 12V 7Ah will supply 7 amps (A) of current for 1 hour before being fully discharged, meaning the battery’s voltage will drop to a point where it should be charged before further use — lest you risk damaging the battery.

Why get into the science of it? Understanding the capacity/time rating can greatly aid in planning an off-grid power solution, as well as not over/undercharging your batteries.

Since most rechargeable batteries are capable of high current delivery, many can deliver currents that will damage the cell from the temperature rise associated with a high rate of discharge. For example, the 12V 7Ah battery used to power a 35W spotlight should not be used to power 600 watts of lighting. A good rule of thumb for sizing most rechargeables to their task is that the current draw in A shouldn’t exceed the battery’s capacity rating (irrespective of hour rating) by more than three to five times, or a 3 C to 5 C discharge rate. Using our example battery to power 600 watts worth of lighting would draw 50 A (over 7 C) from the battery, potentially overheating and causing permanent damage.

411: Nickel cadmium, or NiCad, are one of the most popular rechargeable batteries in use today. Almost everyone uses them. Used in everything from cordless phones to power tools, NiCads supply very high peak currents if needed (discharging more than 5 C in some applications and with specially designed cells) while being rechargeable roughly 1,000 times.

Form: NiCad batteries are available in many common sizes, such as AAA, AA, C, and D. A NiCad cell in these sizes are rated at 1.2V nominal. Capacity varies with cell size; however, the AA samples we used were rated at 1,000 mAh.

Shelf Life: Typical shelf storage losses are approximately 10 percent per month. They should be stored in cool, dry places (not to exceed 85 degrees F). For extended or long-term storage, they should be stored fully discharged. Cells or battery packs left to self-discharge will eventually suffer from the dreaded “memory effect” known as voltage depression due to crystal formation on the cell’s electrodes. Anyone old enough to remember MySpace will have used a cordless phone that showed a full charge but, once removed from the charger, immediately died.

Recharging: Proper cycling is important for long cell life. Without getting too technical, this means simply running the pack to a discharged state before recharging again. It’s best to fully use a NiCad pack’s capacity completely before recharging to ensure the longest pack or cell life.

Crisis Capable?: Because NiCad cells can tolerate a large range of input currents and less-than-ideal charge methods, the ubiquitous “wall wart” household power transformer can accommodate if there’s no other option. Practically every household has a few of them sitting in a junk drawer, legacies to devices that no longer work or were long since thrown out. These simple DC power sources can be wired to a simple battery holder available at electronics stores or, if total improvisation is needed, the leads simply taped or held to the batteries themselves.

### NiMH

411: Like NiCad cells, nickel metal hydride (or NiMH) is ubiquitous in today’s high power electronics, such as two-way radios, professional-grade flashlights, and toys. They’re capable of high discharge rates like the NiCad, but not to the same extent. They are capable of Rapid charging with proper equipment, and are gradually overtaking NiCad in terms of popularity. Quality NiMH cells are typically good for 500-plus recharge cycles.

Form: Like NiCad, NiMH batteries are available in the typical consumer sizes and at a 1.2V nominal rating. One of the primary differences between NiMH and NiCad cells is the capacity of a NiMH cell of a given size is roughly double. The NiMH AA we tested had a capacity of 2,000 mAh, while the NiCad was only 1,000 mAh.

Shelf Life: NiMH cells generally don’t last as long as NiCad. Typically, charge drops off rapidly after the first day, sometimes 5 to 20 percent, then gradually drops to somewhere between 0.5 and 4 percent per day at room temperature. However, there are new NiMH cells out there that claim to be low self-discharge (like the Tenergy cells we sampled) and can maintain a large majority of their charge for over a year. Discharge rates vary greatly with temperature, and if they need to be stored fully charged for long periods. Long-term storage of fully charged packs or cells can be done in the refrigerator, but must be kept in airtight containers to prevent condensation from forming when brought back up to room temperature. These cells are best discharged to 0.9V per cell for long-term storage.

Recharging: It’s best to cycle on a monthly basis if stored. If NiMH cells are stored for long periods of time without charge, they may need to be charged at a 1/10C rate and discharged a few times to regain nominal capacity. NiMH have less tendency to develop voltage depression with improper handling, and cycling can reverse this effect to a greater extent than in the NiCad. Note: Generally, it’s not ideal to charge NiMH or NiCad cells longer than 24 hours and doing so can promote crystal growth and voltage depression.

Crisis Capable?: There are some inexpensive and unique ways to charge both NiCad and NiMH even with no electricity available. We used the low-cost Sunjack 4 AAA/AA charger that plugs into your USB battery or a small solar charger like the SunTactics Scharger-14 Solar Charger. The Suntactics 14W panel can top off a high-capacity USB battery and charge four AAA batteries at the same time. The AAA batteries take about two to four hours to charge, depending if they are NiCad or NiMH.

411: These batteries are the heavy hitters of energy storage. They can be found in everything from handheld spotlights to batteries that run off-grid homes at night. Their ratings are usually in amp-hours (Ah) or reserve capacity (RC) and usually rated nominally at 6 V or 12 V. They’re not particularly portable — unless you’ve won a Strongman Competition or two.

Form: Available in various sizes and capacities. They’re capable of sustained moderate current discharge and deep cycling (full discharge) and not to be confused with automotive batteries, which are capable of high current and very intolerant to deep discharge.

Shelf Life: Lead acid batteries have moderate shelf life and, depending on quality and age of the battery, a self-discharge rate of 3 to 20 percent a month. Overall lifespan seems to be approximately three to five years when properly cared for. Generally, 500 to 800 charge cycles can be obtained within that time. Left discharged for long periods of time they can undergo sulfation, or the crystallization of lead sulfate on the battery’s plates. Early on, it can be reversible, but continued neglect can cause this to become permanent, and the battery’s capacity will degrade over time.

If storing a lead acid battery for extended periods, it’s best to keep it on a trickle (float) charger. A simple DC power adapter rated at 12V would be sufficient to tend a fully charged battery. Even an adapter capable of only a couple hundred milliamps can offset the discharge rate of a large battery, provided the adapter never exceeds approximately 14.5 V — higher than that and electrolyte boiling/gassing can occur. In a gel cell and VRLA (valve regulated lead acid battery), this can cause the battery to swell or explode. It’s always best to use a proper float charger for long-term storage of this battery type and store in a cool dry place.

Recharging: Charging can be done with a small taper charger. Since lead acid batteries vary so greatly in size and can be quite large, it’s important to match charger current to battery. Generally, deep cycle batteries should only be fast charged with a proper tapering current charger. Gel cells are best charged at a 1/10C rate or in some cases slightly faster.

One question that people ask all the time is, “How do I know my battery is charged? I have it hooked up to my generator for 12 hours, and I’m not quite sure.” A deep cycle battery is usually fully charged with a voltage of around 13 V and completely discharged around 12 V.

It’s also vital to know approximately how long it’ll take to conserve fuel. Deep cycle batteries are usually rated in RC instead of Ah. Reserve capacity is the number of minutes a battery can maintain a useful voltage under a 25 A discharge. Our test battery had an RC of 140. This means it can deliver 25 A at a useful voltage for 140 minutes. To get a more useful number, we convert to seconds and multiply by 25 A. The resulting number is the charge in ampere-seconds. Then, we divide by 3,600 to get hours, giving us 58.3 Ah. Therefore, if the charge output of our Yamaha EF2000iS generator is 8 A (58.3 divided by 8), we get almost 7.5 hours of solid power.

Crisis Capable?: If power isn’t available, they can be easily charged with a generator’s secondary DC output, which is usually around 8 A for most manufacturers. There are also many solar charge options available that combine a 50 to 100W panel and small charge controller, such as those manufactured by Renology Solar Suitcase RNG-F-2X50D.

### Alkaline Batteries

411: The most common battery for all electronic appliances. Available everywhere, and most people have dozens on hand. Low to very moderate current capability. While most manufacturers won’t label the capacity of their cells, their capacity is around 3,000 mAh-plus for quality brands. However, it’s important to note that their capacity varies greatly with load. At a 1A draw they may only provide 700 mAh.

Shelf Life: For top quality brands, they could last 10 years or so. It’s best to store alkaline batteries in a cool place, but keeping them in the fridge like mom did isn’t necessary with today’s construction. They self-discharge at a rate of less than 2 percent per year at room temperature. Shelf life will degrade in high temps, though. At 85 degrees F they only lose about 5 percent per year, but at 100 degrees they lose 25 percent per year.

Recharging: Many people don’t know that an alkaline battery can actually be recharged. This should be carried out only with a specialized charger. We sampled the Maximal Power FC999 Universal Rapid Charger, which is capable of recharging alkalines. Charging works best if the batteries aren’t completely dead. We first saw this type of charger emerge in the mid ’80s by a long-gone toy manufacturer. It was the Buddy L Super Charger #8000, which this author still has to this day. While there’s little data on how many recharge cycles the batteries can take, it seems to range from a handful of times to a couple dozen depending on use and load. We advise recharging at your own risk and only with brands recommended by the charger’s manufacturer or top-quality brands.

Crisis Capable?: Extending your disposable battery supply 10 or more times, and combined with how readily available alkaline batteries are, these specialized chargers are definitely worth considering. In desperate times, you could take other people’s dead alkalines and give “good ones” in exchange for other necessities.

### Li-Ion (Polymer)

411: While Li-ion batteries are the stuff of science fiction with energy densities that make grown product engineers weep for joy, they must be properly handled, charged, and protected. Please don’t use any of the aforementioned charge methods unless you have a proper charger suited specifically to Li-ion batteries. Found in smartphones and other high-tech consumer electronics, they commonly require a constant-current, constant-voltage (CCCV) type of charging algorithm and are not compatible with standard constant-current type methods that the other battery types require. Most of the time, you can’t even open a device to access the battery to service it.

Shelf Life: The Li-ion has excellent shelf life. If stored, it should be done so in a partially charged state. Partially discharge a battery to around 50 percent life (usually indicated by the device it’s installed in). Depending on battery quality, they can be stored this way for up to a year.

Recharging: Li-ion doesn’t suffer from a memory effect as with NiMH and NiCad, and can be recharged up to 1,000 full cycles. It’s OK to use a device and recharge the battery even when not completely discharged. These smaller micro cycles do not count as full charge cycles and will not degrade or diminish the battery’s charge cycles significantly. A rough example would be if the battery is only brought to 50 percent every use and then recharged, there may be closer to 2,000 recharge cycles available.

If batteries are stored for long periods of time in a discharged state and look as if they have swelled up don’t attempt to recharge. This could cause a fire or explosion.

Crisis Capable?: While they probably fare the best for holding a charge over long periods of time and potentially have a thousand more charge cycles compared to other battery types, Li-ion aren’t rugged enough or versatile enough to count on during an emergency situation. However, an excellent device to add to your off-grid lifestyle is a ruggedized Li-ion battery that can power USB devices. We used the Limefuel L150XR that includes a 15,000-mAh battery housed in an IP66 water-resistant case and can charge two USB devices at once. The capacity is roughly 10 times that of an average smartphone. Using the SunTactics solar charger we could achieve full charge in a little over 10 hours. This makes a super lightweight rugged power solution for indefinite communications off-grid.

### No Li-Ion King

While lithium-ion (Li-ion) batteries are excellent batteries, their physical and electrical characteristics make them a tough choice in a grid-down situation. Why? Here’s a brief look.

Fragile: You can bend them by hand or easily puncture them, potentially causing a “thermal runaway,” or fire. Water can also permanently damage them or cause a fire.

Size Limit: They’re usually designed with a specific product in mind, so they don’t power other products they weren’t designed for — think batteries for smartphones or certain flashlights. I can still use my 1980s electronics today because they run on AA or C batteries. I can’t use my first-gen iPad with a dead battery that’s barely five years old.

Cell Blocked: Each individual cell is rated at 3.7 V, making combinations less available to power most other electronics. For example, you shouldn’t use a 7.2V 2-cell pack to power your 6V (four-AAA-powered) radio.

Tricky Charges: If a Li-ion is even removable from a device (such as with a digital SLR camera), you will notice there are multiple contacts and not just the usual positive and negative. This is because chargers are also specific to each battery and requires cells to be balanced — the extra contact(s) allow each cell to be charged individually. Overcharging can cause immediate damage or fire.

Discharge Distress: Like a maxed-out credit card that’s never repaid, a Li-ion battery that’s been over-discharged can be ruined. This can occur even after just a couple of times. Fortunately, most electronics designed for these batteries have protection circuitry designed to prevent over-discharge, i.e. The latest smartphones.

Robert Swenson is the owner of Mission Technical Services, an IT company specializing computing, networking, and large-scale battery backup/uninterruptable power systems. He studied electrical engineering at Cal State Long Beach. He has built several electric vehicles and has a lifetime of experience with electric radio control modeling.

### Military Gas Mask 249.95 mirasafety.com EDC Knives from 7.99 smkw.com

Disclosure: These links are affiliate links. Caribou Media Group earns a commission from qualifying purchases. Thank you!

### STAY SAFE: Download a Free copy of the OFFGRID Outbreak Issue

In issue 12, Offgrid Magazine took a hard look at what you should be aware of in the event of a viral outbreak. We’re now offering a free digital copy of the OffGrid Outbreak issue when you subscribe to the OffGrid email newsletter. Sign up and get your free digital copy

Written by Robert Swenson

## Battery

The Battery block implements a generic dynamic model that represents most popular types of rechargeable batteries.

This figure shows the equivalent circuit that the block models.

### Charge and Discharge Characteristics

The circuit parameters can be modified to represent a specific battery type and its discharge characteristics. A typical discharge curve consists of three sections.

The first section represents the exponential voltage drop when the battery is charged. The width of the drop depends on the battery type. The second section represents the charge that can be extracted from the battery until the voltage drops below the battery nominal voltage. Finally, the third section represents the total discharge of the battery, when the voltage drops rapidly.

When the battery current is negative, the battery recharges, following a charge characteristic.

The model parameters are derived from the discharge characteristics. The discharging and charging characteristics are assumed to be the same.

The Exp(s) transfer function represents the hysteresis phenomenon for the lead-acid, nickel-cadmium (NiCD), and nickel-metal hydride (NiMH) batteries during the charge and discharge cycles. The exponential voltage increases when a battery is charging, regardless of the battery’s state of charge. When the battery is discharging, the exponential voltage decreases immediately.

The state of charge (SOC) for a battery is a measure of battery’s charge, expressed as a percent of the full charge. The depth of discharge (DOD) is the numerical compliment of the SOC, such that DOD = 100%. SOC.

For example, if the SOC is:

• 100% — The battery is fully charged and the DOD is 0%.
• 75% — The battery is 3/4 charged and the DOD is 25%.
• 50% — The battery is 1/2 charged and the DOD is 50%.
• 0% — The battery is has 0 charge and the DOD is 100%.

### Model Validation

Experimental validation of the model shows a maximum error of 5% (when SOC is between 10% and 100%) for the charge (when the current is 0 through 2 C) and discharge (when the current is 0 through 5 C) dynamics.

### Parameterization

This figure shows detailed parameters extracted from the Panasonic NiMH-HHR650D battery data sheet.

You can obtain the rated capacity and the internal resistance from the specification tables. The other detailed parameters are derived from the Typical Discharge Characteristics plot.

Nominal Discharge Current (d)

Capacity @ Nominal Voltage (a)

These parameters are approximate and depend on the precision of the points obtained from the discharge curve.

The discharge curves you obtain from these parameters, which are marked by dotted lines in the following figures, are similar to the data sheet curves.

To represent the temperature effects of the lithium-ion (Li-ion) battery type, an additional discharge curve at ambient temperature, which is different from the nominal temperature, and the thermal response parameters are required. Additional discharge curves are not usually provided on the data sheet and may require simple experiments to be obtained. The following examples show parameters extracted from the A123 Li-iron-phosphate ANR26650M1 and the Panasonic Li-cobalt-oxide CGR 18,650 AF battery data sheets.

The A123 ANR26650M1 data sheet specifications include the required discharge curve points and other required parameters.

These parameters are derived from the data sheet for the A123 Li-ion temperature-dependent battery model.

Nominal discharge current

Capacity at nominal voltage (c)

Nominal ambient temperature

Second ambient temperature

Initial discharge voltage at 0°C (e)

Voltage at 90% maximum capacity at 0°C (g)

Thermal resistance, cell-to-ambient (estimated)

Thermal time constant, cell-to-ambient (estimated)

In the figure, the dashed lines show the discharges curves obtained from the simulation at different ambient temperatures. The model performance is very close to the data sheet results.

The same approach for parameter extraction is applied to the Panasonic Lithium-Ion CGR18650AF with these specifications.

These parameters are extracted for the battery model.

Nominal discharge current

Internal resistance (estimated)

Capacity at nominal voltage (c)

Nominal ambient temperature

Second ambient temperature

Initial discharge voltage at 0°C (e)

Voltage at 90% maximum capacity at 0°C (g)

Thermal resistance, cell-to-ambient (estimated)

Thermal time constant, cell-to-ambient (estimated)

The figure shows a good match between the simulated discharge curves (represented by the dashed lines) and the data sheet curves. The accuracy of the model depends on how precise the selected points from the data sheet discharge curves are.

To model a series and/or parallel combination of cells based on the parameters of a single cell, use the parameter transformation shown in the following table can be used. The Nb_ser variable corresponds to the number of cells in series, and Nb_par corresponds to the number of cells in parallel.

Nominal discharge current

Capacity at nominal voltage

### Equations

For the lead-acid battery type, the model uses these equations.

f 1 ( i t. i. i. E x p ) = E 0 − K ⋅ Q Q − i t ⋅ i − K ⋅ Q Q − i t ⋅ i t Laplace − 1 ( E x p ( s ) S e l ( s ) ⋅ 0 )

f 2 ( i t. i. i. E x p ) = E 0 − K ⋅ Q i t 0.1 ⋅ Q ⋅ i − K ⋅ Q Q − i t ⋅ i t Laplace − 1 ( E x p ( s ) S e l ( s ) ⋅ 1 s )

For the lithium-ion battery type, the model uses these equations.

f 2 ( i t. i. i ) = E 0 − K ⋅ Q i t 0.1 ⋅ Q ⋅ i − K ⋅ Q Q − i t ⋅ i t A ⋅ exp ( − B ⋅ i t )

For the nickel-cadmium and nickel-metal-hydride battery types, the model uses these equations.

f 1 ( i t. i. i. E x p ) = E 0 − K ⋅ Q Q − i t ⋅ i − K ⋅ Q Q − i t ⋅ i t Laplace − 1 ( E x p ( s ) S e l ( s ) ⋅ 0 )

f 2 ( i t. i. i. E x p ) = E 0 − K ⋅ Q | i t | 0.1 ⋅ Q ⋅ i − K ⋅ Q Q − i t ⋅ i t Laplace − 1 ( E x p ( s ) S e l ( s ) ⋅ 1 s ).

• EBatt is the nonlinear voltage, in V.
• E0 is the constant voltage, in V.
• Exp(s) is the exponential zone dynamics, in V.
• Sel(s) represents the battery mode. Sel(s) = 0 during battery discharge, Sel(s) = 1 during battery charging.
• K is the polarization constant, in V/Ah, or polarization resistance, in Ohms.
• i is the low-frequency current dynamics, in A.
• i is the battery current, in A.
• it is the extracted capacity, in Ah.
• Q is the maximum battery capacity, in Ah.
• A is the exponential voltage, in V.
• B is the exponential capacity, in Ah −1.

For the lithium-ion battery type, the impact of temperature on the model parameters is represented by these equations.

f 1 ( i t. i. i. T. T a ) = E 0 ( T ) − K ( T ) ⋅ Q ( T a ) Q ( T a ) − i t ⋅ ( i i t ) A ⋅ exp ( − B ⋅ i t ) − C ⋅ i t

f 1 ( i t. i. i. T. T a ) = E 0 ( T ) − K ( T ) ⋅ Q ( T a ) i t 0.1 ⋅ Q ( T a ) ⋅ i − K ( T ) ⋅ Q ( T a ) Q ( T a ) − i t ⋅ i t A ⋅ exp ( − B ⋅ i t ) − C ⋅ i t

• Tref is the nominal ambient temperature, in K.
• T is the cell or internal temperature, in K.
• Ta is ambient temperature, in K.
• E/T is the reversible voltage temperature coefficient, in V/K.
• α is the Arrhenius rate constant for the polarization resistance.
• β is the Arrhenius rate constant for the internal resistance.
• ΔQ/ΔT is the maximum capacity temperature coefficient, in Ah/K.
• C is the nominal discharge curve slope, in V/Ah. For lithium-ion batteries with less pronounced discharge curves (such as lithium iron phosphate batteries), this parameter is set to zero.

The cell or internal temperature, T, at any given time, t, is expressed as:

T ( t ) = L − 1 ( P l o s s R t h T a 1 s ⋅ t c ) ,

• Rth is thermal resistance, cell to ambient (°C/W).
• tc is thermal time constant, cell to ambient (s).
• Ploss is the overall heat generated (W) during the charge or discharge process and is given by

For the lithium-ion battery type, the impact of aging (due to cycling) on the battery capacity and internal resistance is represented by these equations:

• Th is the half-cycle duration, in s. A complete cycle is obtained when the battery is discharged and charged or conversely.
• QBOL is the battery’s maximum capacity, in Ah, at the beginning of life (BOL) and at nominal ambient temperature.
• QEOL is the battery’s maximum capacity, in Ah, at the end of life (EOL) and at nominal ambient temperature.
• RBOL is the battery’s internal resistance, in ohms, at the BOL and at nominal ambient temperature.
• REOL is the battery’s internal resistance, in ohms, at the EOL and at nominal ambient temperature.
• ε is the battery aging factor. The aging factor is equal to zero and unity at the BOL and EOL.

The battery aging factor, ξ, is expressed as

• DD is the battery DOD (%) after a half-cycle duration.
• N is maximum number of cycles and is given by

N ( n ) = H ( D O D ( n ) 100 ) − ξ ⋅ exp ( − ψ ( 1 T r e f − 1 T a ( n ) ) ) ⋅ ( I d i s _ a v e ( n ) ) − γ 1 ⋅ ( I c h _ a v e ( n ) ) − γ 2 ,

• H is the cycle number constant (cycles).
• ξ is the exponent factor for the DOD.
• ψ is the Arrhenius rate constant for the cycle number.
• Idis_ave is the average discharge current in A during a half cycle duration.
• Ich_ave is the average charge current in A during a half cycle duration.
• γ1 is the exponent factor for the discharge current.
• γ2 is the exponent factor for the charge current.

## Examples

### Ni-MH Battery Model

A 200 V, 6.5 Ah Ni-MH battery model during charge and discharge process.

## Ports

### Ta — Ambient temperature Simulink ® signal | scalar

Input port for the ambient temperature.

### Dependencies

To enable this port, set Type to Lithium-Ion and select Simulate temperature effects.

### m — Battery temperature, state-of-charge, current, voltage, age, maximum capacity, and ambient temperature Simulink signal | vector

Output vector of signals for the battery temperature, state-of-charge, current, voltage, age, maximum capacity, and the ambient temperature. To demultiplex the signals, you can use a Bus Selector block.

The cell or internal temperature

Battery SOC, represented as a percentage (between 0 and 100%). The SOC is 100% for a fully charged battery and 0% for an empty battery. The SOC is calculated as:

S O C = 100 ( 1 − 1 Q ∫ 0 t i ( t ) d t ).

### Dependencies

The port outputs signals for:

• Ambient temperature if Simulate temperature effects is selected.
• Cell or internal temperature if Simulate temperature effects is selected.
• Battery age if Simulate aging effects is selected.
• Battery maximum capacity if Simulate aging effects is selected.

### — Positive terminal specialized electrical

Specialized electrical conserving port associated with the battery’s positive terminal.

### – — Negative terminal specialized electrical

Specialized electrical conserving port associated with the battery’s negative terminal.

## Parameters

### Type — Battery model Lithium-Ion (default) | Lead-Acid | Nickel-Cadmium | Nickel-Metal-Hydride

Battery model. The block provides predetermined charge behavior for four battery types. For the Lithium-Ion battery, the block provides models for simulating temperature and aging effects.

### Dependencies

If this parameter is set to Lithium-Ion. these parameters are visible:

### Simulate temperature effects — Thermal dynamics off (default) | on

Select to model thermal dynamics.

### Dependencies

To enable this parameter, set Type to Lithium-Ion. For more information, see Type.

If Simulate temperature effects is selected:

• The input port Ta is visible. For more information, see Ta.

### Use a preset battery — Parameterization no (default) | 3.3V 2.3Ah (LiFePO4) | 3.6V 2050mAh (LiCoO2) | 3.6V 2.0Ah | 3.6V 3.6Ah (LiNiO2) | 3.6V 4.5Ah | 3.6V 48Ah (LiNiO2) | 3.7V 4.4Ah | 7.4V 5.4Ah (LiCoO2) | 11.1V 6600mAh (LiCoO2) | 12.8V 40Ah (LiFeMgPO4)

To model thermal dynamics, the block uses battery-specific temperature parameters.

If you have a license for Simulink Design Optimization™ and empirical battery data, you can:

• Set this parameter to no.
• Estimate the temperature parameters based on the empirical data by using Simulink Design Optimization.
• Specify the parameters in the Temperature settings using the estimated values. For more information, see Temperature.

Otherwise, use preset data that the block provides for a lithium-ion battery.

### Dependencies

To enable this parameter, set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Type and Simulate temperature effects.

If this parameter is set to one of the preset lithium ion batteries, the parameters in the Parameters, Discharge, and Temperature, settings are disabled.

### Simulate aging effects — Model age-related battery capacity deterioration off (default) | on

Select to model age-related battery capacity deterioration.

### Dependencies

To enable this parameter, set Type to Lithium-Ion. For more information, see Type.

If this parameter is selected, the Aging settings are visible. For more information, see Aging.

### Nominal voltage (V) — Nominal voltage 7.2 (default) | positive scalar

Nominal voltage, Vnom, of the battery, in V. The nominal voltage represents the end of the linear zone of the discharge characteristics.

### Rated capacity (Ah) — Rated capacity 5.4 (default) | positive scalar

Rated capacity, Qrated, of the battery, in Ah. The rated capacity is the minimum effective capacity of the battery.

### Initial state-of-charge (%) — Initial SOC 100 (default)

State-of-charge (SOC) of the battery, expressed as a percentage of the maximum potential charge, at the beginning of simulation. An SOC of 100% indicates a fully charged battery and 0% indicates an empty battery.

The specified value does not affect the discharge curve that the block generates if, in the Discharge settings, you click Plot.

### Battery response time (s) — Response time 30 (default) | nonnegative scalar

Response time of the battery, in s, at 95% of the final value. This value represents the voltage dynamics and can be observed when a current step is applied.

The plots show the voltage and discharge current for a battery with a response time of 30 s.

### Determined from the nominal parameters of the battery — Discharge parameter determination on (default) | off

Select to have the block determine the parameters in the Discharge settings based on the values specified for the parameters in the Parameters settings.

### Dependencies

Selecting this parameter disables the parameters in the Discharge settings.

### Maximum capacity (Ah) — Maximum amp-hour capacity 5.4 (default) | positive scalar

Maximum theoretical capacity, Q, when a discontinuity occurs in the battery voltage, in Ah. This value is generally equal to 105% of the rated capacity.

### Dependencies

To enable this parameter, in the Parameters settings, set Use a preset battery to no. For more information, see Use a preset battery.

### Cut-off Voltage (V) — Cut-off voltage 5.4 (default) | positive scalar

Minimum allowable battery voltage, in V. This voltage represents the end of the discharge characteristics. At the cut-off voltage, the battery is fully discharged.

### Fully charged voltage (V) — Fully charged voltage 8.3807 (default) | positive scalar

Fully charged voltage, Vfull, for a given discharge current. The fully charged voltage is not the no-load voltage.

### Nominal discharge current (A) — Nominal discharge current 2.3478 (default) | positive scalar

Nominal discharge current, in A, for which the discharge curve is measured.

For example, a typical discharge current for a 1.5-Ah NiMH battery is 20% of the rated capacity: (0.2 1.5 Ah / 1 h = 0.3 A).

### Internal resistance (Ohms) — Internal resistance 0.013333 (default) | positive scalar

Internal resistance of the battery, in ohms. When a preset model is used, a generic value is loaded that corresponds to 1% of the nominal power (nominal voltage multiplied by the battery rated capacity). The resistance is constant during the charge and the discharge cycles and does not vary with the amplitude of the current.

### Capacity (Ah) at nominal voltage — Amp-hour capacity at nominal voltage 4.8835 (default) | positive scalar

Capacity, Qnom, extracted from the battery until the voltage drops under the nominal voltage. This value should be between Qexp and Qmax.

### Exponential zone [Voltage (V), Capacity (Ah)] — Exponential zone voltage and capacity [7.7788 0.2653] (default) | nonnegative vector

Voltage, Vexp, and the capacity, Qexp, that correspond to the end of the exponential zone. The voltage should be between Vnom and Vfull. The capacity should be between 0 and Qnom.

### Discharge current [i1, i2, i3. ] (A) — Discharge characteristic plot currents [6.5 13 32.5] (default)

The block can generate a figure of two graphs that show the battery discharge characteristics. The discharge characteristics for these currents are presented in the second graph.

### Units — Discharge characteristic plot x-axis units Time (default) | Ampere-hour

Units used for the x-axis of the plots generated by Plot.

### Plot — Plot discharge characteristics

Generate a figure of two graphs that show the battery discharge characteristics. The first graph represents the nominal discharge curve for the specified value for the Nominal Discharge Current parameter. The second graph represents the discharge curves at the specified discharge currents.

### Dependencies

The discharge currents for the second plot are the specified values for the Discharge current [i1, i2, i3. ] (A) parameter. For more information, see Discharge current [i1, i2, i3. ] (A).

The units for the x-axis of the plots are determined by the specified value, Ampere-hour (Ah) or Time. for the Units parameter. For more information, see Units.

### Temperature

The Temperature settings are visible only if, in the Parameter settings, the Type parameter is set to Lithium-Ion and the Simulate temperature effects check box is selected. For more information, see Parameters, Type, and Simulate temperature effects.

The battery provides preset parameter values for common types of lithium-ion batteries. To use the preset parameter values, in the Parameters settings, set the Use a preset battery to parameter to one of the lithium-ion batteries. For more information, see Use a preset battery.

If you use a preset option, the only enabled parameter in the Temperature settings is Initial cell temperature (deg. C). The other parameters in the Temperature settings are disabled because the block provides the values.

Alternatively, if you have a license for Simulink Design Optimization and empirical battery data, you can estimate the temperature parameters for a lithium-ion based. To enable the parameters, In the Parameters settings, set the Use a preset battery to parameter to no.

### Initial cell temperature (deg. C) — Initial battery temperature 20 (default) | scalar

Cell or internal temperature of the battery, in °C at the start of simulation.

### Dependencies

To enable this parameter, in the Parameter settings, set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

### Nominal ambient temperature T1 (deg. C) — Nominal ambient temperature 20 (default) | scalar

Ambient temperature, in °C, at nominal condition of operation. The block assumes that the parameter values provided in the Parameters settings are obtained at this ambient temperature.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Second ambient temperature T2 (deg. C) — Second ambient temperature.30 (default) | scalar

Ambient temperature, in °C, at the second operating condition. This value should be less than the value specified for the Nominal ambient temperature T1 (deg. C) parameter.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Maximum capacity (Ah) — Maximum amp-hour capacity 4.8 (default) | positive scalar

Maximum battery capacity, in Ah, at the temperature specified for the Second ambient temperature parameter T2 (deg. C).

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type parameter to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Initial discharge voltage (V) — Initial discharge voltage 7.1 (default) | positive scalar

Discharge voltage at the second ambient temperature, in V, when the discharge current is first applied.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Voltage at 90% maximum capacity (V) — 90% maximum capacity voltage 5.655 (default) | positive scalar

Discharge voltage at the second ambient temperature when 90% of the maximum capacity is used, in V.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Exponential zone [Voltage (V), Capacity (Ah)] — Exponential zone voltage and capacity [6.58 1] (default) | positive vector

Discharge voltage, in V, and the capacity, in Ah, that correspond to the end of the exponential zone, at the second ambient temperature.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Thermal resistance, cell-to-ambient (deg. C/W) — Thermal resistance 0.6 (default) | positive scalar

Total thermal resistance, in °C/W, between the cell and ambient points of measurement. It is assumed the cell temperature is equivalent to the average internal temperature of the battery.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Thermal time constant, cell-to-ambient (s) — Thermal time constant 2000 (default) | positive scalar

Temperature response time constant, in s, between the cell and ambient points of measurement. You can obtain this value from the ambient temperature step response while the battery is in idle mode.

### Dependencies

This parameter is visible if, in the Parameter settings, you set Type to Lithium-Ion and select Simulate temperature effects. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled if, in the Parameters settings, you set Use a preset battery to no. For more information, see Use a preset battery.

### Heat loss difference [charge vs. discharge] (W) — Heat loss difference 0 (default) | scalar

Power loss difference between charge and discharge, in W, when the battery is charged and discharged at the same C-rate and ambient temperature.

To determine the power loss difference ΔP, use this equation:

Δ P = t c ( θ 2 − θ 1 ) R t h

where θ1 and θ2 are the rates of change of the battery internal temperature (°C/s) during discharge and charge.

### Dependencies

This parameter is visible only if, in the Parameter settings, the Type parameter is set to Lithium-Ion and the Simulate temperature effects check box is selected. For more information, see Parameters, Type, and Simulate temperature effects.

This parameter is enabled only if, in the Parameters settings, the Use a preset battery parameter is set to no. For more information, see Use a preset battery.

### Aging

The Aging settings visible if, in the Parameters settings, you set the Type parameter to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Initial battery age (Equivalent full cycles) — Initial battery age 0 (default) | nonnegative scalar

Battery age or equivalent full cycles at the beginning of the simulation. A full cycle is defined as a complete discharge and charge to 100% DOD and 100% SOC at a nominal ambient temperature and nominal discharge and charge current. Default is 0.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Aging model sampling time (s) — Aging model sampling time 1e6 (default) | positive scalar

Simulation time step of the aging model, in s.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Ambient temperature Ta1 (deg. C) — Ambient temperature 25 (default) | scalar

First ambient temperature. Ta1, during the aging performance test, in °C.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Capacity at EOL (End Of Life) (Ah) — End-of-life amp-hour capacity 5.40.9 (default) | positive scalar

Maximum capacity at EOL at ambient temperature Ta1, in Ah.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Internal resistance at EOL (Ohms) — End-of-life internal resistance 0.0133331.2 (default) | positive scalar

Internal resistance at EOL at ambient temperature Ta1, in ohms.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Charge current (nominal, maximum) [Ic (A), Icmax (A)] — Nominal and maximum charge currents [2.3478, 3] (default) | positive vector

Nominal and maximum charge current, in A.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Discharge current (nominal, maximum) [ID (A), Idmax (A)] — Nominal and maximum discharge currents [2.3478, 10] (default) | positive vector

Nominal and maximum discharge current in A.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Cycle life at 100% DOD, Ic and ID (Cycles) — Cycle life at 100% DOD, Ic, ID, and Ta1 1500 (default) | positive scalar

Number of cycles at 100% depth of discharge, at nominal charge current and discharge current, and at the first ambient temperature, Ta1.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Cycle life at 25% DOD, Ic and ID (Cycles) — Cycle life at 25% DOD, Ic, ID, and Ta1 10500 (default) | positive scalar

Number of cycles at 25% depth of discharge, at nominal charge current and discharge current, and at the first ambient temperature, Ta1.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Cycle life at 100% DOD, Ic and Idmax (Cycles) — Cycle life at 100% DOD, Ic, Id_max, and Ta1 1000 (default) | positive scalar

Number of cycles at 100% DOD, at nominal charge current, at maximum discharge current, and at the first ambient temperature, Ta1.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Cycle life at 100 % DOD, Icmax and ID (Cycles) — Cycle life at 100% DOD, Ic_max, ID, and Ta1 1400 (default) | positive scalar

Number of cycles at 100% depth of discharge, at maximum charge current, at nominal charge current and discharge current, and at the first ambient temperature, Ta1.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Ambient temperature Ta2 (deg. C) — Ambient temperature Ta2 45 (default) | scalar

Second ambient temperature,bTa2, in °C, during the aging performance test.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

### Cycle life at 100% DOD, Ic and ID (Cycles) — Cycle life at 100% DOD, Ic, ID, and Ta2 950 (default) | positive scalar

Number of cycles at 100% DOD, at nominal charge and discharge currents, and at the second ambient temperature, Ta2.

### Dependencies

To enable this parameter, in the Parameters settings, set Type to Lithium-Ion and select Simulate aging effects. For more information, see Type and Simulate aging effects.

## References

[1] Omar N., M. A. Monem, Y. Firouz, J. Salminen, J. Smekens, O. Hegazy, H. Gaulous, G. Mulder, P. Van den Bossche, T. Coosemans, and J. Van Mierlo. “Lithium iron phosphate based battery — Assessment of the aging parameters and development of cycle life model.” Applied Energy, Vol. 113, January 2014, pp. 1575–1585.

[2] Saw, L.H., K. Somasundaram, Y. Ye, and A.A.O. Tay, “Electro-thermal analysis of Lithium Iron Phosphate battery for electric vehicles.” Journal of Power Sources. Vol. 249, pp. 231–238.

[3] Tremblay, O., L.A. Dessaint, Experimental Validation of a Battery Dynamic Model for EV Applications. World Electric Vehicle Journal. Vol. 3, May 13–16, 2009.

[4] Zhu, C., X. Li, L. Song, and L. Xiang, “Development of a theoretically based thermal model for lithium ion battery pack.” Journal of Power Sources. Vol. 223, pp. 155–164.

## Version History

Introduced in R2008a

## Battery calculator for any kind of battery : lithium, Alkaline, LiPo, Li-ION, Nimh or Lead batteries

Enter your own configuration’s values in the white boxes, results are displayed in the green boxes.

## Principle and definitions

### Capacity and energy of a battery or storage system

The capacity of a battery or accumulator is the amount of energy stored according to specific temperature, charge and discharge current value and time of charge or discharge.

Even if there is various technologies of batteries the principle of calculation of power, capacity, current and charge and disharge time (according to C-rate) is the same for any kind of battery like lithium, LiPo, Nimh or Lead accumulators.

### Configuration of batteries in series and in parallel : calculate global energy stored (capacity) according to voltage and AH value of each cell

To get the voltage of batteries in series you have to sum the voltage of each cell in the serie.

To get the current in output of several batteries in parallel you have to sum the current of each branch.

Caution : do not confuse Ah and A, Ampere (A) is the unit for current, Ampere-hour (Ah) is a unit of energy or capacity, like Wh (Watt-hour) or kWh or joules.

The global capacity in Wh is the same for 2 batteries in serie or two batteries in parallel but when we speak in Ah or mAh it could be confusing.

Example :. 2 batteries of 1000 mAh,1.5 V in series will have a global voltage of 3V and a current of 1000 mA if they are discharged in one hour. Capacity in Ampere-hour of the system will be 1000 mAh (in a 3 V system). In Wh it will give 3V1A = 3 Wh. 2 batteries of 1000 mAh,1.5 V in parallel will have a global voltage of 1.5V and a current of 2000 mA if they are discharged in one hour. Capacity in Ampere-hour of the system will be 2000 mAH (in a 1.5 V system). In Wh it will give 1.5V2A = 3 Wh

That is why it is better to speak in Wh (Watt-hour) rather than Ah (ampere hour) when you speak of capacity of a pack of batteries with elements in series and parallel, because capacity in Watt-hour is not linked to the voltage of the system whereas capacity in Ampere-hour is linked to the voltage of the pack of batteries.

### Rating capacity and C-rate

C-rate is used to scale the charge and discharge current of a battery. For a given capacity, C-rate is a measure that indicate at what current a battery is charged and discharged to reach its defined capacity. A 1C (or C/1) charge loads a battery that is rated at, say, 1000 Ah at 1000 A during one hour, so at the end of the hour the battery reach a capacity of 1000 Ah; a 1C (or C/1) discharge drains the battery at that same rate. A 0.5C or (C/2) charge loads a battery that is rated at, say, 1000 Ah at 500 A so it takes two hours to charge the battery at the rating capacity of 1000 Ah; A 2C charge loads a battery that is rated at, say, 1000 Ah at 2000 A, so it takes theoretically 30 minutes to charge the battery at the rating capacity of 1000 Ah; The Ah rating is normally marked on the battery.

Last example, a lead acid battery with a C10 (or C/10) rated capacity of 3000 Ah should be charge or discharge in 10 hours with a current charge or discharge of 300 A.

### Why is it important to know the C-rate or C-rating of a battery

C-rate is an important data for a battery because for most of batteries the energy stored or available depends on the speed of the charge or discharge current. Generally, for a given capacity you will have less energy if you discharge in one hour than if you discharge in 20 hours, reversely you will store less energy in a battery with a current charge of 100 A during 1 h than with a current charge of 10 A during 10 h.

## Formula to calculate Current available in output of the battery system

How to calculate output current, power and energy of a battery according to C-rate? The simplest formula is :

I = Cr Er or Cr = I / Er Where Er = rated energy stored in Ah (rated capacity of the battery given by the manufacturer) I = current of charge or discharge in Amperes (A) Cr = C-rate of the battery Equation to get the time of charge or charge or discharge t according to current and rated capacity is : t = Er / I t = time, duration of charge or discharge (runtime) in hours Relationship between Cr and t : Cr = 1/t t = 1/Cr

## Proper Care and Feeding: NiMH Battery FAQs

A: The material is Nickel Metal Hydride (NiMH) which has many advantages over other battery construction materials.

### Q: What is meant by battery memory?

A: Older generation and batteries with other chemical make-up were subject to a memory effect. This is when a battery must be fully drained before recharge or their capacity is reduced. The New Generation of NIMH batteries do not develop a memory effect and can be recharged at anytime during usage cycle. When uncertain about battery charge level or condition, recharge it.

### Q: What is the mAh rating mean?

A: This is a rating of energy storage capacity mAh = “milli-ampere hours”. So if you are comparing batteries to a AA with a 2000 mAh rating, it will have twice the capacity of a 1000 mAh rating.

### Q: What is the best application for NiMH batteries?

A: Most all applications where there is a high energy consumption and demand, is where NiMH belongs. The most popular applications are digital cameras, flashlights, and toys. If you find yourself constantly buying alkaline batteries for an application, then you should consider using rechargeable NiMH.

### Q: How many times can a NiMH battery be recharged?

A: Lower capacity rechargeable AA batteries of 1700 up to 2000mAh can be recharged up to 1000 times in overnight slow charge mode, while 2100 to 2400 mAh rechargeable batteries can be recharged up to 600 to 800 times in overnight slow charge mode.

The new higher capacity AA 2500 mAh rechargeable batteries have greater power capacity, but they can only be recharged approx 500 times in the overnight mode. Capacity improvement or quick charging will always decrease the number of cycles. Every cell available on the market above 2100 mAh will have below 1000 charge cycles.

### Q: What applications are not good places to use NiMH batteries?

A: Any situation where the battery is not used within a 30 day period or low energy draw devices, for example smoke alarms, emergency flashlights, clocks, TV remotes, etc.

### Q: Why won’t NiMH batteries work in some applications such as smoke alarms?

A: NiMH batteries self discharge about 1% per day so if used in a low energy consummation or stand-by device, the battery will only last about 90 days before requiring recharge.

### Q: Can I use a higher rated mAh battery in my electronic device (i.e. 1800mAh vs. 2000mAh)?

A: Yes, the mAh rating will give you longer run times between recharges. The higher rated mAh of a battery has no effect on electronic devices other than they allow longer term use.

### Q: Why are AA and AAA batteries rated at 1.2 volts and alkaline batteries rated at 1.5 volts?

A: In fact, over the course of their discharge, alkaline batteries actually average about 1.2 volts. The main difference is that an alkaline battery starts at 1.5 volts and gradually drops to less than 1.0 volts. NiMH batteries stay at about 1.2 volts for almost 80% of their discharge cycle. Once alkaline batteries discharge to 50% capacity, it will be delivering a lower voltage than a NiMH battery.

### Q: What you NEVER want to do with replaceable batteries?

• Never mix batteries from different manufacturers
• Never mix batteries of different capacities
• Never mix batteries of different chemistries, i.e. NiCd, NiMH, Lithium, etc.
• Never DROP the battery if you can help it as NiMH batteries damage internally quite easily
• Never store NiMH in the refrigerator
• Never expose to extreme heat

### Q: Do NiMH batteries lose capacity over time?

A: Yes, but nothing drastic. About 10 to 15% of the battery mAh capacity will be lost at the 400 to 800 recharge level. This will vary greatly because of battery and charger quality, along with how the consumer treats their batteries.

### Q: When I receive my batteries do I need to charge them?

A: Yes, before you use them for the first time, you need to charge your NiMH batteries fully. Please note that for new NiMH batteries, it is often necessary to cycle them at least three to five times or more before they reach peak performance and capacity. The first several times that you use your NiMH batteries you may find that they run down (discharge) quickly during use. Don’t worry, this is normal until the batteries actually structure internally.

### Q: Is there a difference in chargers. i.e, fast, slow, microprocessor controlled, etc?

A: Yes, there are differences in the different chargers on the market today. If the charger was designed and sold in the past couple years and specifically says it is made to charge NiMH batteries you are probably okay. Most of the new chargers use a small computer chip to manage the charge and you should be getting at least 500 charges from your batteries. If not, buy a new charger. Some of the no name batteries sometimes have a short life. Fast chargers also tend to give shorter battery life of less than 500 charges.

### Q: How do dispose of old NiMH batteries?

A: This is an easy one! While it is safe and legal in most states to dispose of your NiMH battery in your regular trash, we always encourage recycling whenever possible.

Phil Purnell-WebbMy solar lights use NiMh 1.2v 600mAh batteries. Can I replace them with (say) 2300mAh ones?

TECHYou can go with a higher-capacity battery as long as you stick with the same voltage and chemistry battery.

SherHi. I have a sonic toothbrush with NiMH battery. I fully charged it, thinking my old sonic wasn’t usable. I got the old one working and might not need the new one for a while. Will it damage battery to not use the now-charged new one for maybe a year?

BatteryStuff TechIt is recommended to store NiMH batteries at approximately 40% SOC to reduce age related capacity loss. Most NiMH batteries can be stored at this capacity for 3 to 5 years when stored at this level.

Talia KI have a Philips XL430 cordless phone. Unfortunately I cannot use its NIMH 550 mAh batteries anymore as I have damaged one of them. I have replaced them by two fully charged GP 930 mAh batteries, however the phone does not charge and the screen says ‘no battery’. What can be the reason? Thanks in advance.

BatteryStuff TechTalia, if you match the intended voltage and chemistry and you are getting no battery detected I would theorize that Phillips may be preventing consumers from using after market batteries by putting a chip in the battery to let the phone know its a genuine battery and OK to charge. We have seen this done with laptops and other devices, but to be honest i haven’t seen this done with a phone, although we do not sell phone batteries, so I cannot tell you for sure.

BatteryStuff TechNiMh batteries are used in a lot of solar equipment. Realistically, we recommend sticking with the same voltage and chemistry that came with your solar charging equipment as the solar panel for that unit is most likely geared toward that chemistry.

BatteryStuff TechMost smaller solar lights contain NiMH or Lithium batteries that can be recharged with plug in charger. In the end you just need to verify the charger is meant to charge the that style battery. If you looking for a charger we do carry a couple chargers by Tenergy that are meant to charge smaller cell batteries.

Armand BoisvertI have NIMH batteries that came with my portable phones in 2017 the phone is acting very static breaking up how do I know when it’s time to buy new NIMH batteries

BatteryStuff TechTypically, a reduction in capacity or talk time is going to be the sign its time to replace the battery. However, weak batteries generally aren’t a cause for static. Static on the phone is typically relate to other causes such as weather (moisture on phone lines), faulty cable between wall and receiver, other devices on the phone line (DSL), faulty DSL Filter, or a fault in the house wiring maybe caused by a pest.

JimThe article says i may need to cycle the batteries a few times to get peak charge but it also states not to fully discharge the batteries. How far should they drain before I recharge them to achieve a proper “cycle” to help structure the batteries?

BatteryStuff TechThe article didn’t say you shouldn’t fully discharge the batteries. In fact fully cycling the battery when you first start to use it will help form the battery internally. We recommend you fully cycle them at least three to five times before they reach peak performance and capacity. After that feel free to recharge whenever you see fit, as the these batteries do not have memory effect.

StarkHello I have a remote controlled heli opterbut it seems it has a battery problem it does not charge so one day I removed battery and connected it with dry cell it underperformed but worked,the battery which I removed from helicopter was a small 3.7 v 85 mah rechargeable battery so the question is now which battery do I use in order to replace the helicopter battery and bring back to working plz tell me reply fast

BatteryStuff TechYou want to replace it with the same voltage and chemistry battery. Your mAh can differ, but generally you want to go with one that is the same rating or higher. If you go with a higher rated battery just make sure it will still fit, and be aware it will take longer to charge.

Nona Eboli bought this digital power charger w/ 4 pcs 600mah rechargeable batteries. i tried to charge it but its too hot, both charger and the batteries, am afraid it will blast so i remove the charger. is it ok if its too hot? and can i use the rechargeable batteries to solar garden lights? thanks and more power!

BatteryStuff TechBatteries will generally be warm to the touch during charging, but should be hot. If they are hot than their might be an issue either with the charger, or the batteries. I would contact the manufacturer of our charger to be sure. As far as your solar lights you would want to use the same type of battery that was installed in the light.

WayneI would like to know if I replace my current cordless phone battery with a higher capacity rechargeable battery. For example, currently the battery that comes with the phone is using a 450mah capacity battery. Can I use a 1000mah or even a 2100mah rechargeable battery ? If its possible, does that means that the charging will takes a longer time and the usage time will be longer too ?

BatteryStuff TechAs long as the voltage stays the same you can utilize a higher mAh battery. You are correct in regards that it will simply take longer to charge.

ManuHi, thanks for the article. Can you tell me what happens when you use a rechargeable Ni-mh 2100 with a normal AA battery? Did I damage the Ni-mh? Thanks!

BatteryStuff TechMixing and matching battery chemistry is never recommended it is quite possible it damaged the battery.

ShannonYou do not list cordless phones among the electronic devices that use these rechargeable batteries. I have a Panasonic cordless phone that takes Ni-MH 1.2v AAA batteries. Will any rechargeable Ni-MH AAA work in my phone?

BatteryStuff TechYes, however I would make sure that you replace the battery with a same mAh rating or greater so the phone last as long, or longer.

MedicalGeniusInteresting article. Question: If an EKG machine with an NiMH battery were to be unused for six weeks, what action(s) should one take to prevent premature wear of the accessory? Should the equipment remain plugged in, keeping the battery’s charge at full capacity? Also, what is minimum temperature and/or humidity levels it is safe to store NiMH batteries? Thank you.

BatteryStuff TechWe have posted your question to the forum, but we are unable to offer in regards to support for a medical device. I believe it would be best to contact the manufacturer for their recommendations.

SpongBobQuestion: What temperature and humidity range can a NIMH be safely stored in? We have three EKG machines located in trailers. We would like to lower the temperature within those structures since they won’t be occupied for six weeks. How best can we conserve energy and ensure that the batteries inside the EKG machines aren’t harmed? Should the batteries simply be removed? The units are kept plugged in 24/7. Thank you.

BatteryStuff TechI believe it would be best to contact the manufacturer of the EKG machines and verify their operating temperature. Most manufacturers will provide an operating temperature range for their devices to ensure they work properly.

AmbrishCan I use a battery with higher mAh than originally provided with my camera ? Will the same charger work for new battery as well ?

BatteryStuff TechYou can us a battery with a higher mAh, and the plus side is that it will last longer. However your charger will take longer to recharge a higher capacity battery.

AVGI have just received a new phone battery. Based on other purchase experience When I put it in the phone I know it will contain some charge already. Is it best to charge it fully straight away? or let it run down and then fully charge? thanks

BatteryStuff TechThe New Generation of NIMH batteries do not develop a memory effect and can be recharged at anytime during usage cycle. When uncertain about battery charge level or condition, recharge it.

TepReally like the article! I do have a question about batteries though: I have a device which is running on two AA Duracell batteries. The batteries (brand new) together is producing 3.2 volts (1.62 volts individually), which is estimated to run for at least 2 years. The device is constantly running and consumes about 300 Micro amps, which is not a lot. I was wondering, when might the batteries voltage begin to drop from 3.2 volts to 3.0 volts or lower? After constantly being used for a month straight, will it then begin to drop?

ROZI have a Duracell GoEasy charger (a few years old now) that came with AA NiMH batteries marked with 1700mAh and see newer AA NiMH batteries with 2400mAh. Can I use the newer 2400mAh AA batteries in this charger?

BatteryStuff TechYes, it would just take a little longer for the charger to charge as it is a higher capacity.

MaggieHi there… I replaced my solar garden batteries with new ones. because the old ones would not charge out side in the sun light anymore. ( I Use them in in strings of 50 small bulb fairy garden lights ) I ordered exactly the same batteries that were used in the solar panel for the lights, and they arrived uncharged. My problem is, that although I have put them in a battery charger several times to fully charge, they do not hold their charge for long, and the lights will not work for more than a couple of nights. The bright sunlight does not seem to power them up again during the day light. I have to keep taking them out of the panel to recharge every two to three days which is very annoying as the old batteries gave the lights life for about a year before they died. Any ideas what I am doing wrong ? Thank you so much … Maggie 🙂

BatteryStuff TechIt sounds as if either the light conditions have changed where this string of lights are, or the battery capacity is not the same as before. If the battery capacity is less than before that would mean there was less reserve for bad weather days, which would mean the batteries last less.

## What Are The Different Methods To Estimate The State Of Charge Of Batteries?

There are three methods to estimate the state of charge of batteries: estimation based on voltage, estimation based on current (Coulomb Counting), and estimation from internal impedance measurements.

While finishing up a report on your laptop late at night, you get an alert that your battery is low and that you should plug your charger in. “Just a few more minutes,” you think and continue with your work. Suddenly, you get the hated message that your system’s battery is critically low, and if you do not connect it to a charger, the computer shall turn itself off.

It’s only then that you frantically look for the charging adapter and hopefully protect your unsaved work from a digital catastrophe.

There are so many things that our laptops and smartphones can do that we often take them for granted. Among many other things, almost all modern electronic devices keep tabs on their batteries and tell you, in absolute percentage values, how much charge is left or how long they can be used before they’ll need a recharge.

Have you ever wondered how modern electronic devices do that?

Recommended Video for you:

## How Do Smartphones And Laptops Calculate How Much Charge Is Left In Their Batteries?

Short answer: Accurately determining the amount of charge left in a battery is no easy task, but there are a few methods that can be used, including estimation based on voltage, estimation based on current (Coulomb Counting), and estimation from internal impedance measurements. All these methods rely on measuring a convenient parameter that changes as the battery is charged/discharged. However, all these methods have their own shortcomings, and therefore cannot be relied upon to provide 100% accurate readings of the ‘remaining charge’ in the battery. Also, some of these methods are specific to certain cell chemistries. Before we learn about some of these methods in detail, it’s important to first decipher a term that’s going to appear throughout this article with remarkable consistency. Also Read: Does Letting A Phone Discharge Completely Before Charging It Again Improve Its Battery Life?

## What Is ‘State Of Charge’?

State of Charge, as the name implies, tells you the state of a battery, and more specifically, the charge remaining in a battery, at a given moment. Commonly abbreviated as SOC, it is the equivalent of a fuel gauge for the battery pack in an electric vehicle or hybrid vehicle. Another closely related term to SOC is Depth of Discharge (DOD). It’s actually just the inverse of SOC, i.e., it’s an alternate method to indicate how much of a battery’s charge has been used up. A battery holds charge, and we want to measure how much it holds at a given instant. In other words, we want to determine its State of Charge. This can be achieved through a few methods. Let’s talk about some of them.

### Determining State Of Charge By Measuring The Voltage

A battery’s SOC is often measured by its voltage, as the process is simple and yields fairly accurate results. It basically converts a reading of the battery voltage to SOC and displays it to the user. Let’s try to understand this process with the help of an analogy. A battery is like a tank of water with a faucet at its base. You have no way of looking into the tank, so you can’t know how much water it contains at a given instant. How will you determine how much water is left in the tank? One way of estimating the amount of water left is to look at the pressure of the water coming out of the faucet. If the water comes out fast, it means that it’s under a lot of pressure, signifying that the tank is mostly full. On the other hand, if the flow of water out of the faucet is very slow, you know that the tank is almost empty The same is true in the case of batteries. A Li-ion battery with a voltage of 3.5 V may be 3.6 V when full and 3.3 V when almost empty (i.e., 92-98% of its total capacity has been used). Note that a Li-ion battery can be discharged to 3V and lower, but the battery shows 0% or ‘fully discharged’ at 3.3V to ensure maximum useful capacity of the battery. Discharging the battery below this cut-off voltage can do serious damage to the battery. A device will take this voltage and accordingly estimate how much charge is left in the battery, which is then shown to the user on the screen.

### Problems With SOC Estimation By Voltage

Although the process is simple, it cannot be relied upon to provide 100% accurate results, because certain factors like ambient temperature, discharge rate, cell materials and battery age affect the voltage. Voltage curves in most batteries follow a non-linear curve against state of charge. Furthermore, there’s the problem of hysteresis, which means that the battery keeps discharging itself even after it’s stopped to discharge. To prevent this issue, a battery must be ‘relaxed’ completely for a few hours for the voltage measurement to work accurately. (Source)

### Determining State Of Charge Using Current (Coulomb Counter)

Another method of estimating SOC is to measure the current entering (when it’s being charged) and leaving (when it’s being discharged) the cells and integrating this over time. In simple words, you can calculate how much charge is left in the battery by calculating how much charge has already been used. This technique of determining the SOC is aptly called ‘Coulomb counting’, since it counts the charge entering/leaving the cells. Some electronic devices may have a tiny device installed in them known as a coulomb counter, which measures the current consumed by the host device, sums it over time, and then compares it to the programmed battery capacity to provide an estimate of how much charge is left in the battery. Although it provides more accuracy than most other SOC estimation methods, since it measures the current flow directly, it has its own set of limitations, namely that it does not consider the efficiency of the battery. Also, it’s very difficult (and expensive) to make accurate current measurements (Source).

### SOC Estimation From Specific Gravity (SG) Measurements

This is a very commonly employed method to estimate the SOC of lead acid batteries. It involves using a sensor that measures changes in the weight of the active chemicals present in the battery as it discharges. As the charge stored in the battery is used up, the concentration of sulfuric acid (an active electrolyte in the battery) decreases, which proportionately reduces the specific gravity of the solution. Although hydrometers have been traditionally used to make specific gravity (SG) measurements, modern lead acid batteries consist of electronic sensors that provide real-time SG measurements and yield fairly accurate SOC values. However, this method is quite exclusive to lead acid batteries and cannot be used with other cell chemistries.

### SOC Estimation By Measuring Internal Impedance

The active chemicals inside a cell change their composition as they convert from one form to another during charging/discharging the battery. Therefore, by measuring the internal impedance (the opposition that a circuit presents to a current when voltage is applied) of the cell, its SOC can be determined. However, this technique is not a popular choice: first, the impedance of a cell is temperature dependent; and second, it’s difficult to measure the impedance of a cell while it’s still active. There are a few other methods that can be used to determine the state of charge of a battery, but none of them is perfect, and each offers a unique set of problems. So, it should always be considered that SOC determination methods can provide only an estimate of the state of charge of a battery, and not a 100% accurate value. In other words… keep your charger handy! Also Read: Can Batteries Be Made To Last Longer Than They Usually Do?