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How to use a battery charger

ALWAYS read the charger’s instructions, and remember that not all batteries are compatible with every charger; if your car has a start-stop system, it’ll likely have an Absorbent Glass Mat (AGM) or Enhanced Flooded Battery (EFB) that requires a smart charger, rather than a conventional one.

For information on how to handle your battery, read the car’s handbook. It isn’t necessary to remove the battery – it can be very difficult in some cars anyway – but if you need to, then disconnect the black negative clamp first, then the red positive one by loosening the bolt on the side of each terminal, before tucking the cables out of the way. Loosen the straps and take care when lifting it out, because it’ll be heavy.

If the battery is still in the car, connect the charger’s red lead to the positive battery terminal, while the car’s handbook will advise on whether to clamp the black negative lead to the battery terminal or a part of the car’s body/chassis.

Switch the charger on at the mains. A full recharge could take up to 12 hours, depending on the size of the battery and your charger’s rating – the higher the amps the better. Smart chargers will monitor the battery condition, and switch to a low-voltage ‘maintenance’ charging mode once finished.

If you’ve removed the battery, then reverse the removal process; disconnect the negative lead from the charger first, and connect the positive terminal first when replacing it in the car. Do up the clamps tightly to secure the battery and leads. Once power is restored, you’ll need to check your car’s electrical systems (keyfob, radio codes, etc) still work.

What should you buy?

TWO types of battery charger are available: conventional and smart. The former are usually cheaper, but are only compatible with older-style lead-acid batteries. Smart chargers work with the batteries used in cars with start-stop systems, as well as conventional lead-acid batteries.