Batteries for wearable electronics are small and lightweight batteries that must provide enough power and store enough energy without overburdening the user with their bulk and weight.
The most popular wearable electronics batteries are coin or button batteries, which come in various sizes and chemistries and offer different voltages, discharge currents, and prices.
Most Common Button Batteries Chemistries
Most common button batteries chemistries include various rechargeable and non-rechargeable chemistries, including:
As its name suggests, alkaline, non-rechargeable chemistry is based on alkaline electrolytes, mostly potassium hydroxide (KOH). It offers many benefits compared to older zinc-carbon chemistry, including longer shelf life (2-4 years on average), higher capacity, improved leakage resistance, etc.
Alkaline batteries feature a nominal voltage of 1.5V and a cut-off voltage of 0.8-0.9 volts, although the cut-off voltage often depends on the device being powered.
Zinc-carbon batteries are phased out in favor of alkaline batteries in many battery sizes. However, one of the inherent issues with alkaline batteries is the voltage drop over time, leading to their replacement in many devices with silver-oxide batteries.
Nonetheless, button alkaline batteries are popular for many small, low-power devices, including wearables like kids watches and medical devices.
The typical labels of alkaline button/coin cell batteries are “LR**” or “LR****,” where “**” and “****” are a number part of their labels, for example, LR44 battery or LR1154 battery.
Silver-oxide batteries are non-rechargeable batteries that use silver oxide as the cathode material and, when compared with alkaline batteries, they offer slightly higher nominal voltage (1.55 vs. 1.5V), higher cut-off voltage (1.2V vs. 0.9V), higher capacity, longer shelf life (2-5 years), very stable voltage output, etc. at the expense of somewhat higher price.
Thus, many electronic devices requiring stable voltage and relatively high energy-to-weight ratio use silver-oxide batteries instead of alkaline batteries.
Due to minimal voltage difference, alkaline batteries are often replaced with silver oxide batteries leading to longer runtimes. However, replacing silver oxide batteries with alkaline batteries, especially in sensitive electronics, may lead to not only shorter runtimes (smaller capacity, less energy stored) but also to device glitches and other issues due to the less stable output voltage.
The typical silver-oxide button/coin cell battery labels are “SR**” or “SR****,” for example, SR44 or SR1154.
Lithium Manganese Dioxide (LiMnO2) Chemistry
Lithium Manganese Dioxide (LiMnO2) chemistry is another example of non-rechargeable battery chemistry, which offers higher nominal voltage (3.0V), higher cut-off voltage (2.0V), high capacity, very long shelf life (3-10+ years), and strong pulse currents.
As such, lithium button batteries are often used as CMOS batteries in computers, such as watch batteries, GPS batteries, credit-card size devices, remote controllers, car keys, keychain flashlights, and similar.
The typical label of lithium non-rechargeable button/coin cell batteries is “CR****,” for example, CR2032.
Lithium-ion chemistry is a rechargeable chemistry offering batteries with an output voltage of 3.2-3.7 volts that can withstand 500-1000, sometimes even more charging cycles.
The output voltage depends on the exact battery chemistry – for example, Lithium Iron Phosphate (LiFePO4) batteries feature a nominal output voltage of 3.2V, a typical maximum output current of around 1C, and a typical maximum charging current of 1C.
However, compared with non-rechargeable lithium (LiMnO2) batteries, lithium-ion batteries feature 4-6x smaller capacity and a much faster self-discharge rate (1-5% monthly vs. 1-3% annual self-discharge rate).
Also, lithium-ion batteries must be recharged using battery chargers intended for such batteries, or they may overheat, burst into flames, or even explode!
The typical label of lithium-ion rechargeable button/coin cell batteries is “LiR****,” for example, LiR2032.
Other battery chemistries may also be used, but these are rare.
LR44 battery is a button/coin battery based on alkaline chemistry featuring physical dimensions of (Diameter x Height) 11.6 x 5.4 mm.
Typical LR44 batteries feature a nominal capacity in the 110-130 mAh range, although there are models with capacities over 150 mAh.
According to IEC (International Electrotechnical Commission) standard, alkaline 11.6 x 5.4 mm batteries are labeled as “LR1154” and “1166A” according to ANSI (American National Standards Institute) standard.
Other labels include AG13, A76, 76A, etc., but almost always have “LR44” as part of the battery label/description.
In most devices, LR44 batteries may be replaced with SR44 battery (silver-oxide 11.6 x 5.4 mm battery), which usually features labels SR1154, SG13, SR44SW, SR44W, 303, 357, etc.
When replacing LR44 batteries with batteries labeled as “303” or “357”, one has to note the “303” battery (also often labeled as “SR44SW”) is a low-drain silver-oxide battery suitable for devices such as analog watches, digital watches without LED lights and alarms and similar, while “357” battery (also often labeled as “SR44W”) is high-drain battery suitable even for devices that occasionally require strong current pulses.
Due to technological advances, most battery brands have switched to multi-drain SR44 batteries, making them suitable for both low-drain and high-drain devices.
Despite many advantages of SR44 batteries, LR44 batteries are still strong and are one of the most popular batteries on the planet, according to Google Trends and Ahrefs Keyword Explorer.
Button 11.6 x 5.4 mm batteries may also be found in other battery chemistries, including:
- Zinc-air batteries, typically labeled as 675 battery, PR44 battery, or Blue Tab batteries, with a nominal voltage of 1.4-1.45V and capacity of 600-700 mAh – these batteries are almost exclusively used as hearing aid batteries due to the large capacity, but wet electrolyte that eventually dries out if the battery is activated too soon.
- Mercury-oxide batteries, typically labeled as MR44 or MR1154 batteries, with a nominal voltage of 1.35V and a capacity of 180-200 mAh – due to the mercury content. These batteries are phased out.
LR1130 battery is a non-rechargeable alkaline battery that is very similar to the LR44 battery and features physical dimensions of (Diameter x Height) of 11.6 x 3.1 mm and a nominal capacity in the 50-80 mAh range.
According to IEC (International Electrotechnical Commission) standard, alkaline 11.6 x 3.1 mm batteries are labeled as “LR1131” batteries.
Other labels include AG10, LR54, L1131, and similar, almost always combined with LR1130 battery labels.
Like most alkaline batteries, the LR1130 battery may be replaced with a silver-oxide SR1130 battery (“LR1131” IEC, “1138SO” ANSI), also often labeled as SG10, SR1130W, SR1130SW, 389, 390, etc., which offer longer shelf life, higher capacity (~80 mAh) and more stable voltage, at a somewhat higher price.
Note: SR1130W or 389 batteries are high-drain, and SR1130SW or 390 batteries are low-drain silver oxide 11.6 x 3.1 mm button batteries, often being replaced by newer multi-drain models.
Nonetheless, LR1130 batteries are still more common than SR1130 batteries due to availability and affordability.
Can You Replace LR44 Battery With LR1130 Battery?
Since LR44 and LR1130 batteries feature the same diameter of 11.6 mm and similar height (5.4 mm vs. 3.1 mm), some people may try to replace the LR44 battery with the LR1130 battery, which should not be done for several reasons, including:
- Due to the smaller volume, the LR1130 battery features a smaller capacity and hence can store less energy – the LR1130 battery will not last as long as the LR44 battery.
- LR44 batteries are intended for stronger discharge currents than LR1130 batteries, further shortening the LR1130 battery runtime.
- Due to the lower height, when the LR1130 battery is placed in the LR44 battery compartment, there may be contact issues, and the device may start to behave erratically.
CR2032 battery is one of the most popular non-rechargeable Lithium Manganese Dioxide (LiMnO2) batteries, featuring physical dimensions of (Diameter x Height) 20 x 3.2 mm and a nominal capacity in the 200-250 mAh range. However, some brands claim even higher capacities, for example, Duracell CR2032.
Other typical labels for CR2032 batteries include ECR2032 (Energizer CR2032), DL2032 (Duracell CR2032), VCR2032 (Varta CR2032), etc.
All these labels come with “2032” numbers, describing the battery’s dimensions of 20 x 3.2 mm.
CR2032 is a very popular battery for powering wearable electronics due to its relatively stable output voltage, broad operating temperature range, meager self-discharge rate (often <1% annually), high pulse currents, and affordable prices.
As such, it is commonly found in heart rate monitors, GPS watches, glucose meters, calculators, remote keys, memory backups, and other similar devices.
Although button 20 x 3.2 mm Lithium Manganese Dioxide (LiMnO2) batteries are prevalent, 20 x 3.2 mm button batteries may also be offered as lithium-ion LiR2032 batteries with output voltages between 3.2 and 3.7 volts.
Thus, if a CR2032 battery powers your device, never, but never replace the CR2032 battery with a LiR2032 battery unless clearly stated in the device’s documentation it can be done – a higher voltage of LiR2032 battery may cause not only device issues but may even damage or destroy sensitive devices.
Button 20 x 3.2 mm batteries may rarely be found in other battery chemistries. These chemistries include:
- BR2032 battery: Lithium Carbon Monofluoride non-rechargeable chemistry (2.8-3.0V) offering ultra-low self-discharge rate, broad temperature range, but lower capacity (180-200 mAh), and lower discharge currents.
- ML2032 battery: Manganese Dioxide Lithium rechargeable chemistry (3.0V) offering a capacity of 60-70 mAh and voltage directly compatible with CR2032 batteries.
- VL2032 battery: Vanadium Lithium rechargeable chemistry offers voltage directly compatible with CR2032 batteries (3.0V), generally very similar to ML2032 batteries.
Button/Coin Batteries Safety Issues
Modern button/coin cell batteries don’t contain mercury, lead, cadmium, and similar heavy and toxic elements and are not directly poisonous to humans and animals.
However, when button batteries are swallowed, body liquids short-circuit the batteries, starting the electrolysis, chemical reactions that may cause dangerous chemical burns.
Also, such batteries may cause blockages and other health issues.
Thus, if a button or any similar battery gets swallowed by a human or pet, contact the nearest emergency center or vet and act according to their instructions.
As wearable electronic devices range in size and energy requirements, their batteries range from the most common button batteries like LR44, LR1130, and CR2032 to larger and heavier cylindrical AAA, AA, CR123A, and even 18650 batteries.
Whenever replacing old batteries, be sure the new batteries have the same or compatible chemistry and the same or better performances than the old batteries and the new batteries are in accordance with the devices’ manufacturers’ recommendations.
This article originally appeared on Wealth of Geeks.