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Car battery Amp Hours and CCA: what do they mean?

Amp hours explained: what drains a car battery

The capacity of a battery is measured in amp hours. So, how does it work? Well, an amp hour is the measurement for how long a battery can supply a specified current for, when it isn't being recharged by an alternator.

For example, a 50Ah battery can deliver a current of one amp for 50 hours or two amps for 25 hours if it's not being recharged. The higher Ah rating means the battery has more capacity and can provide power for a longer time.

The car with the 80Ah battery, shown below, can provide a five-amp current for approximately 16 hours before the battery is depleted.

This is why it's vital to get a failed auxiliary belt or alternator fixed as soon as possible, and you should turn off the heater, radio and lights (if possible) to place the lowest possible drain on the battery. Otherwise you'll be stranded.

Find out how to test and charge a car’s battery here.

Amp hour rating and CCA on car battery label

What does Cold Cranking Amps (CCA) mean?

You'll hear more about Cold Cranking Amps (CCA) during the winter because it's a measure of a battery's ability to start an engine in cold temperatures.

It represents the maximum current a battery can deliver for 30 seconds at -17.8°C (0°F) while maintaining a voltage above a specified threshold. The car battery shown above has 800 CCA. This figure is crucial in colder climates, because lower temperatures can reduce a battery's ability to deliver power effectively.

This is why it’s worth taking note of a battery's AH and CCA ratings, because there’s little point in having a vastly powerful battery to power a 1.0-litre hatchback, while at the same time a diesel engine will require a much higher CCA rating than that 1.0 petrol engine.

10 tips to avoid your 12-volt car battery going flat at any time of the year

Follow these 10 tips to ensure your car battery starts the engine without fail every time:

1) Keep the battery terminals clean and free from corrosion (shown below).

Corrosion on car battery

2) Avoid leaving lights, interior electronics, or the radio on when the engine isn't running.

3) Regularly inspect and tighten the battery connections to ensure a secure fit.

4) Park your car in a shaded or covered area during summer to reduce heat stress on the battery.

5) In a severe winter, use a battery blanket or insulating material to maintain a warmer temperature, but make sure it is fitted correctly and isn't in contact with heat sources.

6) A faulty engine stop-start system could be caused by a failing battery (see no.9).

7) Limit short trips that don't allow the battery to fully recharge.

8) If your car will be sitting idle for an extended period, consider using a battery maintainer or trickle charger.

9) Test your battery regularly using a multimeter.

10) If your battery is older or showing signs of weakness, consider replacing it before it fails completely.