In this article, we will be understanding what is meant by a 3V battery, what its common types are, and how capacity of these batteries can be tested. Advantages and challenges associated with various test types are also highlighted.
What is a 3V Battery?
3V or 3 volts battery, as the name indicates, is a type of battery which gives nominal output voltage of 3 volts. These batteries have become significantly popular because of wide use of small electronic gadgets and toys. Many of these gadgets and toys run on small voltage of 3V and require precise supply for smooth and reliable operation. 3V batteries are useful to fulfil this need. In this article, we will be having a detailed look at common types and testing of 3V batteries.
Common Types of 3V Batteries:
3V batteries can be categorized into many types based on shape or external structure, and chemistry. Each type of battery finds its suitable application based on its structure and other characteristics. Here, we will be stating some common types of 3V batteries and their applications.
3V Battery Types w.r.t. Shape:
3V batteries are divided into 3 types on the basis of shape: coin cell, cylindrical, and prismatic.
Coin Cell Batteries:
Coin cell or button batteries have nominal output voltage of 3V so they are regarded as a type of 3V battery. These batteries have different variables available, based on chemistry and size. For example, CR2450, CR2025, and CR2032 are most common examples of 3V coin cell batteries which are widely used in small electronic gadgets, toys etc. With respect to chemistry, CR2450 has lithium manganese dioxide chemistry, CR2025 has lithium ion chemistry, and CR2032 is also non rechargeable lithium ion battery.
Cylindrical Batteries:
Cylindrical 3V batteries are commonly found in small electronic devices. These could also be rechargeable lithium-ion batteries with high energy density. Typical examples of cylindrical batteries are CR123A, CR2, CR1/3N, M52 EX SV, and CR14250BL. These are used for medical devices, toys, cameras, LED flashlights etc. Amongst them, CR123A is lithium manganese dioxide primary battery. CR2 also has chemistry same as that of CR123A and has long shelf life of 10 years. Such battery cell can be used for smart gas meters, leakage detection, portable gas detector, petrochemical facilities, oil and gas tank level monitoring, and mining applications.
Prismatic Batteries:
Prismatic batteries are rectangular shaped thin batteries and are used for devices which are compact. These batteries provide stable 3V voltage and are highly reliable. For example, 3V75AH, sodium Ion battery comes with enhanced safety suitable for critical and expensive applications like tablets, mobile phones etc. It is environment friendly, and scalable for large scale projects. This battery has larger capacity owing to its innovative structure, low internal resistance, stable discharge voltage, high discharge rate, and safest chemistry among all lithium battery types. Prismatic batteries can have LiFePO4 (Lithium Iron Phosphate) chemistry also. These batteries have high energy density, no memory effect, long life cycle (above 500 cycles), and long shelf life (low self discharge).
3V Battery Types w.r.t. Chemistry:
3V batteries might have different chemistries also. Common chemistries for these batteries are as follows.
Lithium manganese dioxide (Li-MnO₂) batteries:
Lithium manganese dioxide (Li-MnO₂) batteries are most common types of 3V batteries. Several variants of coin cell batteries come with this chemistry. CR2032 is a good example of Lithium manganese dioxide (Li-MnO₂) battery. This kind of batteries have high energy density, long shelf life, high pulse capability, suoerior resistance to corrosion, low magnetic signature, and lower cost. These batteries are preferred for high energy applications.
Lithium Iron Phosphate (LiFePO4) Batteries:
Lithium Iron Phosphate (LiFePO4) or LifePO4 prismatic cell battery is used where very stable 3V is required. These batteries are even used in demanding applications like electric bikes. These batteries have good safety feature, and contain no toxic materials. Their discharge rate is low and perform good at higher temperatures. Their recharge ability feature boosts their demand further.
Lithium polymer (Li-Po) batteries:
Li-Po batteries have typical voltage ranging between 3.2 to 4.2V but these can be regarded as 3V battery due to proximity. These batteries also have good energy density. Their shelf life is average/moderate, and operational temperature range is -20°C to +60°C.
Lithium Thionyl Chloride (Li-SOCl₂) Batteries:
These batteries have high energy density, good shelf life, and excellent thermal management. These are light weight and perform well in temperatures ranging from -55°C to 85°C. Lithium Thionyl Chloride batteries can be used for military, industry, medical, and technology applications.
Other Lithium-ion Chemistries:
Though less common, but 3V batteries also come in lithium cobalt oxide (LiCoO2), lithium titanate (Li4Ti5O12), and lithium nickel cobalt aluminum oxide (NCA) chemistries.
Alkaline Batteries:
Alkaline batteries could also have 3V nominal output voltage. Their energy density is moderate and lower than lithium based chemistries. Their shelf life is good and shape is cylindrical. These batteries operate well in temperatures ranging from -20°C to +54°C.
Understanding Capacity and Capacity Testing of a Battery
Battery is a device that stores energy and delivers that energy when required. Mainly, batteries are used as backup devices and their functional capability, evident from their definition, is quantified through ‘Capacity’. Capacity refers to amount of electric charge, a battery can store. It is measured in Ah (Ampere hours) or Wh (Watt hours). Capacity also helps determine time duration for which battery would remain operational under a defined load. A battery with higher capacity can store more energy and keep its load energized for longer period of time. Capacity testing, as the name indicates, is run to measure battery’s ability to store and deliver electrical energy. It is also known as load or discharge test. Capacity test fulfills following purposes:
- Helps determine actual capacity of a battery.
- Helps access battery health. For example, if battery has degraded over time or not.
- Helps determine battery’s performance with load.
- Helps identify weak or malfunctioned cells in a battery pack.
- Helps determine suitability of battery for a specific application.
Capacity Testing for a 3V Battery:
For a typical capacity test, a capacity tester simulates a load. Regardless of battery type and nominal voltage, testing methods remain almost same. But some battery types (depending upon chemistry) need to be tested more carefully because risk associated with them are higher. For example lithium batteries are sensitive towards temperature variations and charge/discharge rates so more complex methods are adopted to run capacity tests for them. Here 3 common ways for measuring battery capacity for a 3V battery are stated.
- Constant Current Method
This method is used for lead-acid batteries normally. For this test, battery is connected with constant current load and time is measured which battery takes to get discharged to a cut-off voltage. Then using formula Capacity (Ah) = Current (A) X Time (Hours); capacity is calculated. This method for capacity calculation is simplest of all other methods and requires least complex equipment. Repeated constant current tests give consistent results, indicating reliability for this test. Anyhow, one must ensure maintaining constant and suitable environmental temperature to get accurate results.
- Constant Power Method
Constant resistance method is little complex testing method and needs to be done carefully to achieve accurate results. For this test, a resistor is connected across battery terminals and voltage is measured across load/resistor after regular intervals. Later on, Ohm’s Law and addition formulas are used to calculate capacity of connected battery. As battery keeps discharging, its voltage drops, so does current through resistor; so it becomes hard to interpret results. Anyhow, if attached resistance/load is constant power load, then current will increase as voltage will drop. So this method is very helpful for such applications. Some batteries experience variable voltage during discharge, constant power method is suitable for such batteries. Here, constant power load is attached with battery and time is noted until cut-off voltage. Then using formula Capacity (Wh) = Power (W) X Time (Hours); capacity is calculated. This testing method is very useful for simulating real-world conditions like batteries in UPS systems. This test also provides insight into overall battery performance at a constant load. Another advantage of using this battery capacity test is generation of Ragone plots elaborating relationship between battery’s specific energy and specific power.
- Constant Resistance Method
Constant resistance method is little complex testing method and needs to be done carefully to achieve accurate results. For this test, a resistor is connected across battery terminals and voltage is measured across load/resistor after regular intervals. Later on, Ohm’s Law and addition formulas are used to calculate capacity of connected battery. As battery keeps discharging, its voltage drops, so does current through resistor; so it becomes hard to interpret results. Anyhow, if attached resistance/load is constant power load, then current will increase as voltage will drop. So this method is very helpful for such applications.
Advanced Method for Battery’s Capacity Testing:
Sometimes, simple methods are not sufficient to give highly precise results or time taken to test each battery makes it impractical to test hundreds of batteries through above mentioned methods. For example, at manufacturing sites thousands of batteries are tested on daily basis or at R&D facilities, tests need to be run repeatedly and quick (but accurate) results are needed to proceed. Similarly, in such scenarios, multimeters are not sufficient as testing equipment. Instead, capacity testers are required. These capacity testers are usually capable of simulating load, monitoring voltage, and making calculations. Here, electrochemical impedance spectroscopy (EIS) is discussed with regard to capacity testing for any battery, specifically a 3V battery.
Electrochemical Impedance Spectroscopy (EIS):
EIS or Electrochemical Impedance Spectroscopy gives insight into electrochemistry of a battery and helps determine its parasitic circuit elements. It can be used during cell manufacturing, R&D, or quality control at later stages. EIS is done for overall health check including capacity assessment of the battery. Further advancement to EIS is regarded as multi-model electrochemical impedance spectroscopy or Spectro. This technology performs around 40 million transactions or calculations because it scans the battery with low amplitude signals at high frequency (20 to 2000 Hz). It is a non destructive technique and it can separate different electrochemical processes taking place in battery and analyzing each individually. Anyhow, running EIS is more complex than other capacity measurement tests so expertise are also needed to interpret data and execute test procedure successfully.
Conclusion
In this article, readers got to learn about 3V or 3 volt batteries. We discussed types of 3V batteries on the basis of chemistry and shape or construction. For each shape type, available chemistry variants, their key advantages, and models are mentioned. For different chemistries, applications and important characteristics are highlighted. Moreover, term ‘capacity’ for a battery is explored and aspects associated with capacity testing are discussed. Three basic capacity testing methods – constant current method, constant power method, and constant resistance method – are discussed briefly. Procedure, advantages, challenges, and suitability for all three types are also discussed concisely. Moreover, EIS (Electrochemical Impedance Spectroscopy) is discussed as advanced technique for capacity calculation, highlighting that it is utilized for quick but accurate results.
FAQs
- How long does a 3V battery last?
Service life of a battery depends upon its chemistry, capacity, and type of use (if battery is providing current constantly or intermittently) primarily. So there is no definite answer to this question. Instead, you would need to consider all mentioned factors and look for more specific answer.
- Can you recharge a 3V battery?
Some 3V batteries might be rechargeable, but some might be not. For example, CR2032 is non rechargeable, but some prismatic, polymer batteries are rechargeable. Recharging capability of a battery depends upon its chemistry so you must know the chemistry of your battery to determine if it can be recharged or not. Moreover, rechargeable battery will be clearly labelled as rechargeable battery.
- Can one measure battery capacity with a multimeter?
Yes, capacity can be measured using multimeter. For this, you will keep checking battery voltage until it reaches cut-off voltage during discharging process. Anyhow, measuring capacity using multimeter is not very accurate method.
- What is the unit of battery capacity?
Capacity is measured in Ampere-hours (Ah) and watt hours (Wh) typically. Your choice of unit will depend upon testing method and application.