Battery Reserve Capacity Explained: Time of Sustained Constant Loads. Auto battery amp hours

What happens if I put a higher amp battery in my car?

Before answering this question, we are going to give some brief technical notes:

Every battery has two main characteristics: Voltage (V) and Capacity (Ah).

Voltage of a battery (V)

The voltage of a battery is the difference in potential or voltage that exists between its poles.

If we consider Ohm’s Law: Voltage = Intensity Resistance we have:

Resistance: It is the resistance offered by what we connect to the battery. If we connected a direct cable from one terminal to another, the battery would give its maximum current intensity. For this reason, it is very dangerous to connect any current conducting element between the two battery terminals. Be careful, therefore, with connecting a direct cable, putting something metallic between the two terminals, or even spilling water on the battery.Intensity: It is the force that the battery can provide at all times.Voltage: As the resistance of what we have connected to the battery is fixed, the higher voltage we have, the more current we can provide. Or put another way, the voltage will determine the current intensity and the higher the voltage, the more intensity we will give.Some conclusions can be drawn from all this:

In a car, everything that is connected to the battery is prepared to operate at a voltage of 12V. What would happen, therefore, if we could connect a 24V battery or 2 12V batteries in series? After all that has been seen, the answer is simple: if we double the voltage, the current intensity would also increase twice and we would run the risk of burning or damaging everything that is connected to the battery.

Likewise, if the battery were to discharge, the current intensity would decrease and the engine would not be able to start, some circuits would not receive enough energy to function correctly, etc.

Important: Never connect a higher voltage battery to the vehicle

Capacity of a battery (Ah)

On the other hand, the capacity of a battery, which is measured in Ah, represents the amount of electricity that a battery can provide. The more capacity (Ah) a battery has, the more electricity it can provide.

In theory, a battery that has 100Ah could give a current intensity of 100 Amps for 1 hour, an intensity of 1 Ampere for 100 hours, or 2 Amps for 50 hours. However, this is not always the case, as the faster a battery discharges, the more power it loses. Therefore, it is common to find batteries that have the following capacity:

Varta LA95 Battery Capacities
Ah 20hr 95Ah
Ah 10hr 90Ah
Ah 5hr 85Ah

That is, the same battery could give 4.75A for 20 hours (4.75A x 20 hours = 95Ah c20), 9A for 10 hours (90Ah c10) or 17A for 5 hours. If we did not have the power losses, the battery should have been able to provide 19A for 5 hours (95Ah) or 9.5A for 10 hours (95Ah).

  • The capacity of a battery is the energy that the battery can provide.
  • The more capacity a battery has, the more energy we can get from it.
  • The faster we discharge a battery, the less energy we can obtain from it.

Therefore, answering the initial question, if we replace a car battery with a higher capacity one, we will be able to leave the elements that depend on the battery in operation for a longer time. In addition, with the same consumption the higher capacity battery will discharge less, which in the long run will result in a longer battery life.

Is there a problem if we install a higher capacity battery?

Although this is not always the case, because the battery design can be different, a battery with a higher capacity will also have a higher CCA, which could be said to be the maximum intensity it can provide in an instant. That does not mean that he is able to provide it in all situations, only when the team needs it.

And this is where we can find the problem: if the equipment is faulty, has a ground problem or a short (connection of positive and negative), the battery with greater capacity will provide more intensity than a normal one and could damage part of the electronics ( although electronic systems are usually protected by fuses, precisely to avoid these situations).

But this effect will only be very apparent if the difference in CCA is considerable. For example, taking it to an extreme, the problem could occur if we try to start a motorcycle with a truck battery and we have some kind of ground or connection problem.

Under normal circumstances, there should be no problem installing a larger capacity battery. On the one hand, there is usually not enough space to install a battery with a large starting difference (CCA) and, on the other, by starting with a greater capacity (Ah) and starting force (CCA), we will increase the battery’s durability since both parameters degrade over time.

In short, if we install a higher capacity battery, we will increase battery life, improve starting and, in addition, we will be able to use the electronic equipment of our vehicle for a longer time.

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However, what happens if we don’t have a space to install a larger battery?

For these cases, manufacturers usually manufacture batteries of different benefits for the same size. The most basic range usually has less ah and the highest range contains the highest performance, both in amp hours and starting capacity.

For example, Varta for the same size has a battery of 70Ah, another of 74Ah and another of 77Ah. The lowest range is the 70Ah and the highest range is the 77Ah. In these cases, the manufacturer always recommends installing the highest-end (77Ah), especially if the car has a large number of electronic components.

Battery Varta E13 12V 70Ah: Size: 278x175x190 Battery Varta E11 12V 74Ah: Size: 278x175x190 Battery Varta E44 12V 77Ah: Size: 278x175x190

In short, whenever you have the opportunity to choose, install a battery with the highest possible capacity

Battery Reserve Capacity Explained: Time of Sustained Constant Loads

For those without extensive electrical experience, buying a battery can feel a bit overwhelming. With all the different styles, sizes, and brands, it can be easy to throw up your hands and buy the one suggested by someone else. But understanding the specifications of batteries can go a long way toward helping find the correct battery. One specification you may have seen is battery reserve capacity. Here’s why it’s so important to understand for your next battery search.

What Is Battery Reserve Capacity?

Reserve capacity is simply the time in minutes that a 12V lead-acid battery can sustain a 25 amp load and remain above 10.5 volts.

When evaluating batteries, it’s essential to make sure buyers are comparing apples to apples. That’s where battery reserve capacity (also called RC) comes in. The longer a fully charged battery runs before dropping below a specific voltage, the higher the battery reserve capacity. Most types of traditional lead-acid batteries display this measurement.

At a high-level reserve, capacity is a more accurate measurement of how long a lead-acid battery will last under a sustained load than its amp-hour rating. This rating will be much lower than the actual capacity of the battery primarily due to the Peukert effect.

Need a refresher before we dive in? Check out Amps, Volts, and Watts: Differences Explained in Simple Terms

What Do CCA and RC Mean on a Battery?

RC stands for reserve capacity and is commonly seen on deep-cycle lead-acid batteries. It’s critical to note that reserve capacity measurement is done at 80 degrees Fahrenheit — optimal temperature conditions for a battery.

CCA is a completely different measurement that is specific for vehicle starting applications. CCA stands for “Cold Cranking Amps”. As opposed to battery reserve capacity, CCA is measured in amps, not minutes. It shows how many amps a battery will deliver over 30 seconds at 0 degrees Fahrenheit without dropping below 7.2 volts. This is critical information to know when starting a vehicle to make sure the engine gets enough power from the battery to turn over in less than ideal conditions.

It’s important to note that CCA has nothing to do with battery capacity and will not indicate if a battery is useful for deep discharges. A starting battery is constructed very differently than a deep cycle and is intended for short bursts of energy only followed by an immediate recharge.

How Is Reserve Capacity Calculated?

Battery reserve capacity measures time so you will see it depicted in minutes. To calculate the RC of a battery, the battery has to have a full charge first. Then, manufacturers draw 25 amps of power from the battery at 80 degrees F until it drops below 10.5 volts. The number of minutes it takes for this to occur is the battery’s reserve capacity.

What Is A High Reserve Battery?

Much like the name implies, high reserve batteries are batteries that can provide reserve capacities higher than average. These batteries often produce a lower but still usable charge, meaning the overall capacity will last longer.

These are useful for those who consistently use large amounts of battery capacity between charges. They’re also good for those who may leave their batteries unused for extended periods. High reserve batteries are more likely to retain some energy even after sitting idle for a while. This helps avoid unexpected dead batteries.

Is Reserve Capacity the Same as Amp Hours?

No, these are separate measurements that reflect different things. For one, reserve capacity is a simple measure of time, while amp-hours measures the number of amps a battery can provide over an hour-long period.

However, these two measurements are related, and you can convert one to the other. Divide the RC by 60, and then multiply this number by 25 to obtain the amp hours. If you have the amp hours, divide this number by 25, and then multiply that number by 60 to find the battery reserve capacity.

Keep in mind that this doesn’t quite mean equal energy, as the measurements and conversions don’t take voltage into account.

Do Lithium Batteries Have Reserve Capacities?

Yes, lithium-ion batteries have reserve capacities, but they’re not typically rated or referred to that way. With lithium batteries, amp hours or watt-hours are the standards of comparison.

Lead-acid batteries will see a lower reserve capacity due to the 25-amp draw and the Peukert Effect. The Peukert Effect shows how traditional lead-acid batteries see decreased capacity as the rate of discharge increases. High-quality lithium like our Battle Born line does not suffer significantly from the Peukert effect and the amp hour rating of the battery is the actual amount of charge you can get from the battery under most conditions.

There’s another important thing to note about maxing out battery reserve capacity levels in lead-acid batteries. Reaching the full RC will draw the battery down to 10.5 volts, which is lower than 50% of charge. This is a level that will dramatically shorten lead-acid battery life if reached regularly. Therefore, consider RC more of an upper limit than a target range.

While it’s not a published number you could say our 100AH battery has a 240-minute reserve capacity even though the battery will never go below 10.5 volts. The internal BMS would shut it off before then. It’s important to keep in mind that a 240-minute drain on a Battle Born will not harm the battery as it would with a lead-acid battery.

Why Is It Important to Know About Battery Reserve Capacity?

RC is important only when looking at lead-acid deep cycle batteries intended for use in a long discharge situation. For engine starting applications, RC has no benefit and CCA is the measurement that is more important.

When choosing a battery, it’s critical to know whether it’ll meet day-to-day needs and how far it can push in emergencies. Battery reserve capacity is one of the most valuable ways to quantify this with lead-acid. While different manufacturers and types of batteries may each promise confusing or unclear benefits, RC makes it simple to make an apples-to-apples comparison.

While both CCA and RC numbers are just a small part of choosing the correct battery (along with type, brand, size, and other considerations), it’s vital to understand their roles.

Battery Reserve Capacity Explained

Deciding on which battery to invest in for your energy system can be daunting. There are countless specifications to compare. from amp-hours to voltage to cycle life to efficiency. Another specification, battery reserve capacity, is important to understand, as it can greatly impact the battery’s lifespan as well as determine how the battery will perform under sustained loads. In general, battery reserve capacity indicates how long a fully charged battery can run without dropping below a specific voltage, as it is especially important to know in the event that you need a battery for consistent loads over time, as opposed to short bursts. Below we’ve compiled key information you should know about reserve capacity before investing in your next battery.

What is battery reserve capacity?

Commonly referred to as RC, reserve capacity is the amount of time, in minutes, that a 12V battery can run before dropping to 10.5V. It is measured in reserve minutes. For example, if a battery has a reserve capacity of 150, that means it can supply 25 amps for 150 minutes before the voltage drops to 10.5V.

Reserve capacity differs from amp-hours (Ah) in that reserve capacity is simply a measure of time, whereas amp-hours measure the amount of amps, or current, that can be produced in one hour. You can calculate reserve capacity from amp-hours, and vice versa, as they are related, but they are not the same thing. When comparing the two, RC capacity is a much more accurate measurement of how long a battery will last under sustained loads as opposed to amp-hours.

Why is battery reserve capacity important?

Reserve capacity is used to understand how long you can run your batteries with consistent loads. It becomes very important to understand if you intend to discharge your batteries for a longer period of time and it is a great indicator of battery performance. If you know your reserve capacity, you will have a better understanding of how long you can use your batteries, and how much power you will be able to leverage. Whether you have a reserve capacity of 150 minutes or 240 minutes is a big difference and can drastically change how you use your batteries as well as how many you may need. If you’re spending a full day on the water fishing, for example, you should know how much power and time you’ll have with your battery so that you can time your travel effectively and get home without running out of juice.

Reserve capacity directly impacts the power you are able to generate with your battery. Since power is equivalent to amps multiplied by volts, if your battery voltage drops from 12V to 10.5V, the power drops. Also, since energy is equivalent to power times the length of time used, if the power drops, so does the energy produced. Depending on how you intend to use your battery. such as for days-long RV trips, or for an occasionally used golf cart, you will have different reserve capacity needs.

How does reserve capacity differ between lithium lead acid batteries?

First, while lithium batteries do have reserve capacities, they are not usually rated or referred to this way, as amp-hours or watt-hours are the more common ways lithium batteries are rated. That being said, lead acid batteries have a lower reserve capacity on average than lithium batteries. This is because lead acid batteries exhibit the Peukert Effect in which their reserve capacity decreases as the rate of discharge decreases. The Peukert Effect does not apply to high-quality lithium batteries, and the amp-hour rating of these lithium batteries is the actual amount of charge you can receive from the battery under the majority of conditions.

Specifically, the average reserve capacity of a 12V 100Ah lead-acid battery is around 170-190 minutes, whereas the average reserve capacity of a 12V 100Ah lithium battery is about 240 minutes. Lithium batteries offer higher reserve capacity at the same Ah rating, so you can cut down on space and weight by installing lithium batteries instead of lead acid. Our RB100 has a reserve capacity of 240 minutes at 25 amps, offering higher capacity and longer-lasting power at a fraction of the weight. The RB100 is also just 30 pounds, compared to a 12V 100Ah lead acid battery that weighs 63 pounds.

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To learn more about how to calculate your energy needs and find the optimal battery for your application and usage, visit our Lithium Battery Selector Tool. If you need additional help determining the optimal battery for your specific use case. from boating to your next RV trip, our experts are available to walk you through the process. Contact a member of our team today to get started.

battery, reserve, capacity, explained, time

How Many Amp Does a Car Battery Have? – Here’s the Answer

A battery is essential for cranking an engine and energizing various electronic components inside and outside your automobile. With that in mind, you might wonder how many amp does a car battery have.

In reality, there is no simple answer to this question. However, in most cases, 550 to 1000 amps and 40 to 65 Amp Hours are the ratings you will see. If you want to understand the significance of these estimates, reading this entire article might be helpful.

How Much Amp Does a Car Battery Provide?

The amperage of a car battery is the total amount of current it can provide. Most products indicate this rating on their label as it is one of their important specs.

As mentioned above, the normal amps for car battery use are 500 to 1000 amps. However, this rating will differ, depending on the type of model you have in your car.

Using the amp hours rating divided by current loads per hour, you can identify how long your battery will last. For example, if you have a 100 Ah battery and a load of 5 amps per hour, your battery will last up to 20 hours before it drains.

As you can see, discharge loads are a big factor in battery drains. If you look at an amperage chart online, you can see that the higher discharge, the quicker the battery gets drained.

In the 100 Ah example above, if you use 50 amps of loads per hour instead of 5 amps, your battery will only last for 120 minutes.

Furthermore, the amp hours of a battery are not always consistent. There are factors that can reduce the battery’s capacity, which we will explore below.

Factors that can Decrease Battery Capacity

Usually, as the battery gets old, its health also decreases, which is why the amp hours decline. This fact is why some old batteries easily drain.

Normally, moderately warm temperatures ensure the highest efficiency.

Under cold temperatures, the battery capacity slightly decreases, which is why during winter, its power may not be enough to energize the electrical components of your car.

What is the Battery Reserve Capacity?

A battery reserve capacity, often known as RC, is a time measurement that describes how long a 12V battery can support a 25 amp load before being drained to 10.5V.

Typically, the higher the reserve capacity, the longer you can use it. This RC rating is just as significant as the CCA (Cold Cranking Amps) rating, which you should consider when selecting a new battery.

What is the Ampere Rating of a Car Battery?

The ampere rating is the current capacity of a battery, which is rated chiefly from 550 to 1,000 amps.

This rating is not the same as the amp-hour in a 12 volt car battery label. In short, amp-hour combines the duration we use a battery with the amount of current discharged in one hour.

Aside from these terms, you should also know the following:

  • Cranking Amps – or CA is the amount of current that a fully charged battery can produce for 30 seconds without a voltage decrease. over, there is also a Cold Cranking Amps (CCA) rating, which is higher than a normal CA and important to consider when you need to start a car engine in cold areas.
  • PulseHot Cranking Amps – (PHCA) is the maximum amount of current that a battery can generate for 5 seconds after starting up.
  • Maximum Charging Current – is the maximum amount of current a battery can receive for recharging.

How Do You Measure Car Battery Amps?

Measuring the amps of a battery will tell you whether it is functional or needs replacement. However, to test car battery amps with multimeter, you must first understand Ohm’s law and determine the battery voltage.

  • So, to check car battery amps, connect a multimeter to the battery and note down the voltage reading (make sure the red probe goes to the positive terminal and the black probe to the negative one).
  • Next, you can divide the voltage by the ohm rating to find the amperage.

If you think getting the amps and volts is a bit complicated, there is a much easier way to identify your car battery amp. Determine the battery charge level or the State of Charge (SOC) to know how to tell its amp rating.

For this method, you only need to check how many volts the battery is. A reading of 12.6v and above means the battery SOC is at 100%, 12.4V is 75%, 12.2V is 50%, 12V is 25%, and anything less than 11.9V is considered a flat or dead battery.

For example, a 12.2V measurement indicates that your battery is 50% charged. In this scenario, if your battery’s total amp capacity is 800 amps, it is now only 400 amps.

How Many Amps to Charge a Car Battery?

Typically, 2 amps will work fine, though you can go for a car battery charger with a higher rating, up to 10 amps and even more. In any case, make sure to pick a full battery charger with protection against overcharging and other faults.


Knowing how many amp does a car battery have will help you determine how efficient it is. over, it is also helpful to figure out when you should charge your battery or replace it if necessary.

If you’re having a problem with your car power source, don’t just throw it away. You can use a pulse repair charger to fix it or call your best mechanic to verify the problem.

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