ALKALINE BATTERY

'Alkaline batteries' are a type of power cell dependent upon the reaction between zinc and manganese dioxide (Zn/MnO₂).
Compared with traditional zinc-carbon batteries, while both produce approximately 1.523 volts per cell, alkaline batteries have a higher energy density and longer shelf-life.
Compared with silver-oxide batteries, which alkalines commonly compete against in button cells, they have lower energy density and shorter lifetimes.

Contents

Chemistry

Capacity

Leaks

See also

References

External links

Chemistry

In an alkaline battery, the anode (positive side) is made of zinc powder (allows more surface area for increase rate of reaction therefore increased electron flow) and the cathode (negative side) is composed of manganese dioxide. When describing standard "A", "AA", "C", "sub-C" and "D" type cells, the anode is the raised "button" end while the cathode is the flat end.
So far, they are comparable to zinc-carbon batteries, but the difference is that alkaline batteries use potassium hydroxide (KOH) as an electrolyte rather than ammonium chloride or zinc chloride.
The half-reactions are:^[1]
:$mathrm\{Zn\; (s)\}\; +\; 2\; mathrm\{OH^-\; (aq)\}$
ightarrow mathrm{Zn(OH)_2 (s)} + 2 e^-
and
:$2\; mathrm\{MnO\_2\; (s)\}\; +\; mathrm\{H\_2O\; (l)\}\; +\; 2\; e^-$
ightarrow mathrm{Mn_2O_3 (s)} + 2mathrm{OH^- (aq)} .

Capacity

Unlike NiMH rechargeable batteries, alkaline batteries are normally not sold with a nominal capacity. Alkalines have a high internal resistance, and a high thermal coefficient of resistivity - the faster you drain an alkaline, the higher percentage of the load it dissipates as heat. Therefore, the capacity of an alkaline battery is strongly dependent on the load, even at moderate loads. An AA-sized alkaline battery might have an effective capacity of 3000 mAh at low power, but at a load of 1000 mA, which is common for digital cameras, the capacity could be as little as 700 mAh.^[2]

Leaks

Over time, alkaline batteries are prone to leaking potassium hydroxide, a caustic agent that can cause respiratory, eye and skin irritation. This can be avoided by not mixing different battery types in the same device, replacing all of the batteries at the same time, storing in a dry place, and removing batteries from devices for storage.

See also

★ Rechargeable battery

★ Rechargeable alkaline battery

★ List of battery sizes

References

1. Battery FAQ at www.powerstream.com
2. Alkaline Drain Chart at greenbatteries.com

External links

★ Alkaline batteries

★ Proper battery disposal and recycling