Batteries

All you need to know about batteries.

Summary

There are various types of battery based on different chemistries. To get the best out of them and to avoid problems you need a basic understanding of their advantages and disadvantages, as well as a little about purchasing, maintaining and disposing of them.

Safety

• Old batteries often leak, causing corrosions of the battery contacts, so preventing new batteries from working.
• Lithium batteries can catch fire and burn violently if over-charged, shorted, punctured, or physically damaged in any way.
• Button cells must be kept away from small children. If swallowed, this is a medical emergency as death can result in just a few hours, as a result of electrochemical action in the stomach.

How batteries work

(You can skip this section if you like, though a little more knowledge than you actually need is always helpful.)

Non-rechargeable (primary) batteries

Type	Advantages	Disadvantages	Comments
Zinc carbon and zinc chloride	Cheap. Available in standard shapes and sizes.	Short life and slow death.	Zinc chloride is a heavier duty version of zinc carbon. Alkaline batteries are preferred in almost all applications.
Alkaline	Good life at a reasonable cost. Available in standard shapes and sizes, and also as button cells as cheap alternatives to silver and mercury.		This is the most economic general purpose type.
Silver oxide	High capacity	Expensive	Normally only available in small sizes as button cells for watches and calculators, on account of the cost.
Zinc-air	Very high capacity	Short life once the tab has been remove to activate it by letting the air in	Used in hearing aids in the form of button cells.
Lithium	Very long shelf and service lives.	Relatively expensive.	Various different lithium-based chemistries have somewhat different characteristics. Mainly used in smoke alarms and cameras.

Rechargeable (secondary) batteries

Type - Nominal voltage	Advantages	Disadvantages	Comments
Lead Acid - 2V	Rugged and reasonably cheap.	Lead is toxic and cannot be disposed of in landfill.	At its best when mainly kept fully charged, hence widely used for (petrol/diesel) car batteries, uninterruptable power supplies, emergency lighting, security alarms, but also used in milk floats, golf buggies etc. Smaller sizes generally come as non-spillable sealed units.
Nickel Cadmium (NiCd) - 1.2V	Very rugged Can deliver a high current and accept a very fast charge	Contains cadmium, which is toxic Repeated partial discharge causes a "memory effect"	Mainly used nowadays in power tools and radio controlled model boats and cars.
Nickel Metal Hydride (NiMH) - 1.2V	Greater capacity than NiCd No toxic cadmium No memory effect Available as direct replacements for common sizes of non-rechargeable batteries	Relatively high self-discharge rate Low self-discharge variants have reduced capacity May not work in all equipment designed to accept alkaline batteries on account of a lower voltage (1,2V as opposed to 1,5V for alkaline)	NiMH has replaced NiCd in all but specialist applications.
Lithium - 3.7V	Very high energy density	Very dangerous if abused. Protection circuitry is essential	As with primary lithium batteries, there are various chemistries and formulations with somewhat different characteristics.

External links

• Battery University