Cars are bursting with hi-tech gadgets, and there’s never been so much strain on a battery. Alarms, immobilisers and other kit take a continual load from the power supply, meaning new units can go flat if the car’s not used for a while.

The most important factor when battery shopping is the physical dimensions – expressed as a three-digit code. Here, we tested the 063 size, one of the most common. Other figures include cranking amps (CA) – the maximum current a battery can give out in one go – and amp hours (AH), the total amount of electricity a battery can hold.

Premium AGM (Absorbent Glass Mat) batteries are expensive but very powerful, and will still start an engine even if they’re considerably discharged.