Button cell
Button cells are used to power small portable electronics devices such as wrist watches, pocket calculators, and remote key fobs.
[citation needed] Mercuric oxide button cells were formerly common, but are no longer available due to the toxicity and environmental effects of mercury.
Button cells are dangerous for small children, as when swallowed they can cause severe internal burns and significant injury or death.
Sometimes different cells of the same type, size and capacity are optimized for different loads by using different electrolytes, so that one may have longer service life than the other when supplying a relatively high current.
[citation needed] Alkaline batteries are made in the same button sizes as the other types, but typically provide less capacity and less stable voltage than more costly silver oxide or lithium cells.
This varies for individual types; one manufacturer (Energizer) offers three silver oxide cells of the same size, 357–303, 357-303H and EPX76, with capacities ranging from 150 to 200 mAh, voltage characteristics ranging from gradually reducing to fairly constant, and some stated to be for continuous low drain with high pulse on demand, others for photo use.
[citation needed] Mercury batteries also supply a stable voltage, but are banned in many countries due to their toxicity and environmental impact.
If the powered equipment requires a relatively high voltage (e.g., 1.3 V) to operate correctly, a silver cell with a flat discharge characteristic will give much longer service than an alkaline cell—even if it has the same specified capacity in mAh to an end-point of 0.9 V. If a device seems to "eat up" batteries after the original supplied by the manufacturer is replaced, it may be useful to check the device's requirements and the replacement battery's characteristics.
Examples: Some coin cells, particularly lithium, are made with solder tabs for permanent installation, such as to power memory for configuration information of a device.
A typical use for a small rechargeable battery (in coin or other format) is to back up the settings of equipment which is normally permanently mains-powered, in the case of power failure.
For example, many central heating controllers store operation times and similar information in volatile memory, lost in the case of power failure.
It is usual for such systems to include a backup battery, either a disposable in a holder (current drain is extremely low and life is long) or a soldered-in rechargeable.
The battery reacts with bodily fluids, such as mucus or saliva, creating a circuit which can release an alkali that is strong enough to burn through human tissue.
[17] In 2020, Duracell announced that they were coating some of their lithium button cells with a bitterant compound to discourage children from ingesting them.
[19] The presenting symptoms of button cell ingestion may be misdiagnosed and attributed to common non life-threatening childhood maladies.
In early 2013 the European Parliament Environment Committee voted for a ban on the export and import of a range of mercury-containing products such as button cells and other batteries, to be imposed from 2020.
