Car

Picking the right car battery in three steps

Step one is physical: the tray under the bonnet dictates how long, wide and tall the case may be, and the clamp needs the same base ledge as the original. Step two is orientation, because a plus post on the wrong side leaves the leads short. Step three, and only then, is the electrical rating.

Reading the data table

• Amp-hours: stay level with the factory battery or go a touch higher if the car is loaded with gadgets.
• EN cranking amps: a higher number makes frosty starts easier, and diesels appreciate the margin.
• Chemistry: flooded for conventional cars, EFB or AGM wherever the manufacturer fitted them. Cars that stop the engine at lights have their own section, Start-Stop.

Quick answers

Is a bigger amp-hour rating a problem?

No, provided the case fits and the posts sit on the correct side. The alternator just needs a little longer to refill it.

Where does my battery code come from?

From the sticker on the unit now under your bonnet, or from the original fitment listed in the handbook. Then search brand plus code. Popular makers here include Varta, Exide and Tudor.