Button cell

A button cell is in electrical engineering, an electrochemical cell ( colloquially battery) with a round cross -section, the total amount is less than the total diameter, and emits cell voltages from 1.35 to 3.6 volts. She received her designation by the design that resembles a button clothing in size and shape. After the electrode material, a distinction, inter alia, silver oxide, mercuric oxide and lithium cell.

Button cells are used as a voltage source with devices that have low power requirements, such as buffered SRAM chips on motherboards, or in devices that are very small, such as calculators, watches and hearing aids.

The first button cells were mercury -zinc cells and were introduced in 1942 by Samuel Ruben for the U.S. military.

• 2.1 lithium button cells
• 2.2 Alkaline Button Cells
• 2.3 silver oxide button cells
• 2.4 zinc - air button cells
• 2.5 mercury button cells

Areas / Distinction

Use

Basically, there are also requirements for different types of batteries, which differ from the voltage curve up to the shelf life and should be used accordingly. In Wristwatches are usually silver-oxide batteries and all-round applications, such as in small LED flashlights or children's toys, there are the less expensive alkaline batteries.

Differences

Lithium coin cells are used wherever one needs for a long time, a voltage supply, such as the CR2032 in computers motherboards to ensure a backup battery power to the clock and the CMOS-RAM when the machine disconnected from the mains or is switched off. Also, CR2016, CR2025 etc. are commonly used lithium coin cells are used in smaller electronic devices and in many car keys.

Alkaline manganese button cells are very inexpensive and are therefore often used with LED technology in small electronic devices such as calculators and also in flashlights. Because these batteries can leak, should it be used not as a substitute in a wristwatch. Designations such as L1154, LR44, V13GA, AG13, KA76, LR44H and GPA76 designate a single alkaline battery.

In Wristwatches are in most cases silver oxide button cells with names such as SR1154, SR44, SR44SW or 303 in use. In a few cases there are also watches with lithium batteries, but then so are strikingly large ( eg CR2320 ).

A distinction within these types, the ampacity:

Low- Drain: Reduced current capacity, for example, suitable for watches with high leakage resistance (electrolyte: sodium hydroxide solution).

High - Drain: Higher current - carrying capacity, such as suitable for photo / remote control applications, with good leakage resistance (electrolyte: potassium hydroxide).

Zinc - air button cells are primarily used in hearing aids (see also hearing aid battery ).

Dimensions

Identical dimensions do not mean that it is the right battery. Some providers call for a wide variety of product names that the dimensions are indeed identical, but different types of batteries ( silver oxide 1.55 V, 1.5 V Alkaline, Zinc Air 1.4V ) such as SR41, AG3, SG3, LR41, PR41, 192, 384, 392 describe. In such collections are silver oxide watch batteries, alkaline button cells and zinc-air hearing aid batteries listed as supposedly compatible.

It is possible to use a rated as superior battery as a replacement for an inferior. As silver oxide cells, can also be used instead of the alkali -manganese cells. Accordingly, therefore, may be referred to as the high-order compatible. However, this compatibility does not work automatically in the reverse direction.

Voltage

The voltage of a button cell is dependent on their chemical composition.

* Batteries containing mercury are no longer manufactured.

Capacity

The smaller the button cell, the lower is the amount of charge contained in the cells, in mAh ( mAh) is specified. Despite the very small capacity button cells can have one in years to determing runtime especially in wrist watches and pocket calculators (LCD ) liquid crystal display.

Silver oxide cells usually have a higher rated capacity than alkaline manganese cells.

Structure of the model numbers

Lithium button cells

= CR1620 lithium battery with 16 mm diameter and 2 mm height. The "CR " stands for a lithium battery as a round cell, followed by the diameter in mm, the last digits indicate the thickness in 1/10 mm to. For the lithium button cells, no proprietary designations have spread.

Alkaline Button Cells

LR1154 = alkaline battery with 11.6 mm diameter and 5.4 mm height. The "LR" stands for an alkaline battery as a round cell, followed by the diameter in mm (rounded down), the last digits indicate the thickness in 1/10 mm to. A variety of names are mentioned and partly mixed together again for this coin cells. So there are even packages on which the names SR44, LR44, 357 and L1154 called in a row. This is, for example, an alkaline and silver oxide battery. The batteries have the same dimensions.

Silver oxide button cells

= SR626 silver oxide battery with 6 mm diameter and 2.6 mm height. The "SR" stands for a silver oxide battery as a round cell, followed by the diameter in mm ( rounded down). The last digits indicate the thickness in 1/10 mm. These batteries are mainly used in wristwatches. The advantage of silver oxide batteries is the constant tension for a long time. Basically, silver oxide batteries are made only as button cells.

Zinc - air button cells

Zinc -air batteries have a very high energy density. They are externally visible to the mostly color sealing sticker that keeps the time required for the chemical process air to the activation of the battery. These is the approximately horizontal Endladungskurve that drops steeply until the end capacity and the relatively high current output. These cells are mainly used in hearing aids.

Mercury button cells

These button cell batteries formerly often used are prohibited due to the risk from mercury contained high levels of pollution in Europe. For some types, there are comparison models on zinc air, alkaline-manganese or silver oxide basis. In the individual case must be examined here is whether the higher voltages of the comparison types pose a problem for the device.

Overview sizes and types of batteries

Names of different button cells are standardized in EN 60086. But there are popular names that have been developed by individual manufacturers.

LD Low Drain

HD High Drain

Rechargeable Button Cells

Button cells are also available as rechargeable batteries (short ) battery, come, etc. for use in computers, laptops, cordless phones, headsets, hearing aids. The nominal voltage of nickel- cadmium batteries or nickel -metal hydride batteries is 1.2 volts. In Europe, nickel -cadmium button cells are now banned and therefore completely disappeared from the market. See Directive 2002/95/EC (RoHS).

In a few cases, rechargeable lithium - ion batteries are used in watches.

Button cells and toddlers

Button cells should, like all small parts are kept safe for children. Especially with full button cells not only by the size (comparable to the ingestion of coins ), but also by the voltage contained a danger. Especially dangerous are relatively large button cells with a high voltage in the medical literature, the model is often called CR2032 (3 V typical 200 mAh).

Another danger is that it may cause burns in the area of ​​esophagus, stomach and intestine by leakage of the button cell ..