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Anatomy of a car battery

Anatomy of a car battery

Dan is an experienced motoring journalist who has more than 20 years of experience. He has been the editor of titles such as Fast Ford and Redline, and his latest project was converting an old Renault Trafic into a family campervan.

The technology used in cars is incredibly advanced, but battery technology is still basically the same as it was when your grandpa first started driving.

Sure there have been advances in the way batteries are assembled, making them more powerful and safer – but the basic premise is the same as it ever was.

Lead plates are suspended in an electrolyte solution (a mix of water and acid). A chemical reaction between the plates and the solution generates electrons which flow out via the terminals on top of the battery.

There are variations to the component parts, but the principle is the same across all automotive batteries.

Anatomy of a car battery

You may also have heard of AGM batteries, this stands for Absorbent Glass Mat. In an AGM battery the electrolyte solution is absorbed by very fine fibreglass matting which renders the battery spill-proof.

There are also Gel batteries, where the electrolyte is mixed with silica to form a viscous, jelly-like substance.

Gel batteries can be mounted at any angle, as the electrolyte will not leak out. Both these battery types are often referred to as 'sealed',  or 'maintenance free'.

How to read a car battery label

Batteries are sold in standard sizes, and come with different ratings for Ah (Amp hours) and CCA (Cold Cranking Amps).

Ah refers to the length of time the battery can deliver a continuous specified current –  with the engine switched off a 70Ah battery would power your lights for longer than a 60Ah battery.

CCA related to amount of amps the batteries can deliver at -17deg C for 30 seconds without dropping below 7.2v.

This means that the more CCAs the better the car will start in very cold temperatures. You can upgrade your battery to one with more Ah and CCAs than the standard battery if you wish.

It's unwise to fit a battery with lower 'ratings' as you could quickly find it ceases to become effective.