BU-303: Confusion with Voltages
A battery is an electrochemical device that produces a voltage potential when placing metals of different affinities into an acid solution (electrolyte). The open circuit voltage (OCV) that develops as part of an electrochemical reaction varies with the metals and electrolyte used.
Applying a charge or discharge places the battery into the closed circuit voltage (CCV) condition. Charging raises the voltage and discharging lowers it, simulating a rubber Band effect. The voltage behavior under a load and charge is governed by the current flow and the internal battery resistance. A low resistance produces low fluctuation under load or charge; a high resistance causes the voltage to swing excessively. Charging and discharging agitates the battery; full voltage stabilization takes up to 24 hours. Temperature also plays a role; a cold temperature lowers the voltage and heat raises it.
Manufacturers rate a battery by assigning a nominal voltage, and with a few exceptions, these voltages follow an agreed convention. Here are the nominal voltages of the most common batteries in brief.
Lead Acid
The nominal voltage of lead acid is 2 volts per cell, however when measuring the open circuit voltage, the OCV of a charged and rested battery should be 2.1V/cell. Keeping lead acid much below 2.1V/cell will cause the buildup of sulfation. While on float charge, lead acid measures about 2.25V/cell, higher during normal charge.
In consumer applications, NiCd and NiMH are rated at 1.20V/cell; industrial, aviation and military batteries adhere to the original 1.25V. There is no difference between the 1.20V and 1.25V cell; the marking is simply preference.
Lithium-ion
The nominal voltage of lithium-ion is 3.60V/cell. Some cell manufacturers mark their Li-ion as 3.70V/cell or higher. This offers a marketing advantage because the higher voltage boosts the watt-hours on paper (voltage multiplied by current equals watts). The 3.70V/cell rating also creates unfamiliar references of 11.1V and 14.8V when connecting three and four cells in series rather than the more familiar 10.80V and 14.40V respectively. Equipment manufacturers adhere to the nominal cell voltage of 3.60V for most Li-ion systems as a power source.
How did this higher voltage creep in? The nominal voltage is a function of anode and cathode materials, as well as impedance. Voltage calculations include measuring the mid-way point from a full-charge of 4.20V/cell to the 3.0V/cell cutoff with a 0.5C load. For Li-cobalt the mid-way point is about 3.60V. The same scan done on Li-manganese with a lower internal resistance gives an average voltage of about 3.70V. It should be noted that the higher voltage is often set arbitrarily and does not affect the operation of portable devices or the setting of the chargers. But there are exceptions.
Some Li-ion batteries with LCO architecture feature a surface coating and electrolyte additives that increase the nominal cell voltage and permit higher charge voltages. To get the full capacity, the charge cut-off voltage for these batteries must be set accordingly. Figure 1 shows typical voltage settings.
Figure 1: Voltages of cobalt-based Li-ion batteries.End-of-charge voltage must be set correctly to achieve the capacity gain.
Battery users want to know if Li-ion cells with higher charge voltages compromise longevity and safety. There is limited information available but what is known is that, yes, these batteries have a shorter cycle life than a regular Li-ion; the calendar life can also be less. Since these batteries are mostly used in consumer products, the longevity can be harmonized with obsolescence, making a shorter battery life acceptable. The benefit is longer a runtime because of the gained Wh (Ah x V). All cells must meet regulatory standards and are safe.
The phosphate-based lithium-ion has a nominal cell voltage of 3.20V and 3.30V; lithium-titanate is 2.40V. This voltage difference makes these chemistries incompatible with regular Li-ion in terms of cell count and charging algorithm.
What does CR2032 Stand for?
CR2032 stands for a lithium battery(round shape) having a 20 mm diameter and 3.2 mm thickness.
- The letter C indicates the chemical composition of the battery (here ie, lithium chemistry)
- The letter R indicates the shape of the battery (here ie, Round)
- The first two digits indicate the battery’s diameter in millimeters (here ie. 20mm)
- The second two digits indicate the battery’s thickness (here ie. 3.2mm)
What is a CR2032 Battery?
CR2032 battery falls under the category of primary batteries. Although they are non-rechargeable, their rechargeable version is also available- LIR2012.
It uses lithium as the anode and compounds from the air such as cupric oxide, manganese oxide, oxygen, etc as the cathode. It is easy to recognize the terminals of the CR2032 battery. The rough texture end is the negative terminal and the opposite flat surface is the positive terminal which is indicated on the battery as ‘’.
While most of the batteries produce a nominal voltage of 1.5V, the nominal voltage of CR2032 is 3V. As these are small in size and produce high power, the weight-to-power ratio of CR2032 is very high. The self-discharge tendency is also very low.
Power stability is another celebrated characteristic. This is due to its low internal resistance. This enables its high conductive electrolyte to provide stable power at normal room temperatures as well as at high-low temperatures.
As these batteries are carried in sealed cases, they are leak-poof to a large extent. Since no toxic elements like mercury or cadmium are added, they do not harm the environment. But the cost and damage due to overcharging are considered significant limitations.
CR2032 Battery Equivalent/alternative/replacement
The CR2032 battery can be replaced with 5004LC, BR2032, CR2032H, L2032, AWI L14, DL2032, ECR2032, EA2032C, BR2332, KCR2032, KECR2032, LF1/2V, LM2032, RFA-35, and SB-T15.
Some other equivalent CR2032 batteries are CR2025, CR2016, CR1632, CR1620, CR1616, CR1220, and CR1216. But keep in mind that you will have to make some mechanical adjustments in order to use one of these in place of CR2032.
What is a CR2032 Battery used for?
Since CR2032 batteries are very compact and small in size, they are very suitable for tiny devices. With the larger nominal voltage and high power capacity, they are efficiently utilized for a large number of commercial as well as medical purposes. Some of the important applications of CR2032 batteries include:
- Motherboards to security system panels
- Car key fobs
- Watches
- Calculators
- PDAs
- Electronic organizers
- Garage door openers
- Toys
- Door chimes
- Pet collars
- LED lights
- Sporting goods
- Stopwatches
- Pedometers
- Calorie counters
- Hearing aid
- Glucose monitors
- Tensiometers
- Clinical thermometer
Things to Know Before Testing
In this section, you’ll be able to learn two methods to test battery voltage.
Initial testing is a quick and easy method to test the voltage of a watch battery. But when testing with load, you can observe how the particular battery reacts to the load.
In this case, 4.7KΩ of load will be applied to the battery. This load might vary according to the type and the size of the battery. Choose the load according to the discharge characteristics of the battery. (1)
Method 1 – Initial Testing
This is a simple three-step testing process that requires only a multimeter. So, let’s get started.
Step 1- Set Up the Multimeter
First and foremost, set the multimeter to DC voltage settings. To do that, turn the dial to the VDC symbol.
Step 2 – Placing Leads
Then, connect the multimeter red lead to the positive side of the battery. Next, connect the black lead to the negative side of the battery.
Identifying the Positive and Negative Sides of a Watch Battery
On most watch batteries, there should be a plain side. That is the negative side.
The other side displays a plus sign. That is the plus side.
Step 3 – Understanding the Readings
Now, check the reading. For this demonstration, we use a Lithium battery. So, the reading should be close to 3V, given that the battery is fully charged. If the reading is below 2.8V, you might need to replace the battery.
Method 2 – Testing with Load
This test is a little different from the earlier tests. Here, you’ll have to use the variable resistance box, red and black connectors, and the multimeter. As mentioned earlier, in this test, we are applying a 4.7KΩ with the help of a variable resistance box.
Tip: A variable resistance box is capable of providing a fixed resistance to any circuit or electrical item. The resistance level might range between 100Ω and 470KΩ.
Step 1 – Set Up the Multimeter
First, set the multimeter to DC voltage settings.
Step 2 – Connect the Variable Resistance Box to the Multimeter
Now, use red and black connectors to connect the multimeter and the variable resistance box.
Step 3 – Set the Resistance
Next, set the variable resistance box to 4.7KΩ. As mentioned earlier, this resistance level might vary according to the type and size of the watch battery.
Step 4 – Placing Leads
Then, connect the resistance box’s red lead to the positive side of the watch battery. Connect the resistance box’s black lead to the negative side of the battery.
Step 5 – Understanding the Readings
Finally, it is time to check the readings. If the reading is close to 3V, the battery is in good health. If the reading is below 2.8V, the battery is not good.
Keep in mind: You can apply the same process to a Silver Oxide or Alkaline battery without much trouble. But, remember initial voltages of Silver Oxide and Alkaline batteries are different compared to the above demonstration.
Wrapping Up
Whatever the battery type or the size, always remember to check the voltage according to the above testing processes. When you test a battery with a load, it will give a good idea of how the particular battery reacts to a load. So, it is an excellent method to identify good watch batteries. (2)
Take a look at some of our related articles below.
References(1) battery – https://www.britannica.com/technology/battery-electronics(2) good watch – https://www.gq.com/story/best-watch-brands
Video Reference
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Silver oxide button battery
The positive electrode of the silver oxide button battery is a cell formed by pressing silver oxide and graphite (sometimes manganese dioxide is added to the positive electrode), which is closely connected to the nickel-plated steel cylinder, and the negative electrode is zinc powder (amalgam), potassium hydroxide or sodium hydroxide aqueous solution containing saturated zincate is used as electrolyte, and the contact surface with zinc is usually a steel cylinder plated with Sn or plated with Cu. The content of zinc powder in the zinc amalgam is 2% to 15%. The casing of the battery is typically composed of layers of copper, tin, stainless steel, nickel-plated steel, or nickel. The discharge reaction of the silver oxide coin cell is as follows.
Figure 2 shows the construction of a silver oxide coin cell battery using the SR44 type as an example.
The discharge voltage of silver oxide batteries is very stable and is one of the high-performance batteries. Since the positive electrode active material uses a silver compound, the cost is relatively high and the recycling value is relatively high.
Silver oxide batteries have been widely used as power sources for cameras and desktop electronic computers. In recent years, due to technological progress, they have been gradually replaced by lithium batteries and alkaline button batteries. At present, it is mainly used as a power source for quartz watches. Although the output is small, it also affects environmental protection.
Mercury oxide button battery
The mercury oxide button battery is sealed with a steel container, and the positive electrode is a cell formed by pressing mercury oxide and graphite, which is closely connected to the nickel-plated steel cylinder. The electrolyte is potassium hydroxide or sodium hydroxide solution, and the contact surface with zinc is usually a steel cylinder plated with Sn or plated with Cu. Some varieties use brocade instead of zinc for some specific purposes, such as data logging of natural gas and oil wells, and telemetry and alarm systems for engines and other heat sources. The discharge reaction of a mercury oxide coin cell battery is as follows.
Figure 3 shows the structure of a mercury oxide coin cell battery.
Mercury oxide button battery has the characteristics of flat discharge, stable, high capacity and long discharge time. Because the mercury content is as high as 30%~50%, it is highly dangerous to the environment and human body, and also has a high recovery value.
Zinc-air button battery
Zinc-air coin cells generate electricity directly from the oxygen in the air. Oxygen in the air diffuses into the cell and is then used as a reactant for the cathode. The cathode consists of loose zinc powder mixed with an electrolyte (sometimes with an adhesive). The electrolyte is about 30% potassium hydroxide solution. Figure 4 shows the structure of a zinc-air coin cell battery.
Button-type lithium battery
Button-type lithium batteries mainly include lithium-manganese dioxide button batteries and lithium-ion button 135 button batteries.
Lithium-manganese dioxide button battery is a kind of disposable battery with lithium as anode, manganese dioxide as cathode, and organic electrolyte. The main features of this kind of battery are high battery voltage, rated voltage is 3V (2 times that of general alkaline batteries); termination discharge voltage is 2V; specific energy is large; discharge voltage is stable and reliable;
It has good storage performance (storage time of more than 3 years), low self-discharge rate (annual self-discharge rate 2%); operating temperature range.20~60℃.
Lithium-manganese dioxide button batteries are small in size, generally 12.5~24.5mm in diameter and 1.6~5.0mm in height. Commonly used in clocks, calculators, electronic notepads, cameras, hearing aids, electronic game machines, IC cards, backup power supplies, etc.
Figure 4 shows the construction of a lithium-manganese dioxide coin cell battery.
Lithium-ion button batteries are rechargeable batteries, and they account for a small number of lithium-ion batteries and are not very common.
The elements contained in button-type lithium batteries are quite different from other button batteries, and basically do not contain harmful components such as mercury and cadmium, so they can be treated together in lithium batteries.
In addition to button-type lithium batteries, the other four button batteries contain mercury, nickel, cadmium and other toxic and harmful components. These toxic and harmful substances can pollute soil, water or air in various ways. Eating or drinking contaminated food or water, inhaling contaminated air, or directly contacting and absorbing through the skin can harm human health.
Although mercury-free zinc powder has been applied in recent years, making alkaline batteries into a green battery, China is also gradually making regulations on the range of mercury content in various types of batteries, promoting the production of mercury-free batteries, and striving to control the environmental pollution of batteries from the source, the mercury content in button batteries still accounts for a large proportion. As for now, since there are still a large number of old-fashioned battery manufacturers in China, it is difficult to completely achieve mercury-free in a short period of time. Therefore, for button batteries (except button-type lithium batteries), it is necessary to carry out classified collection and recycling.