How to choose a car battery: the five figures that decide everything

A battery is not chosen by price or by brand, but by five technical parameters. Get one of them wrong and the battery either will not fit the tray, or the cables will not reach the terminals, or it will live in permanent undercharge and die within two winters.

1. Capacity, Ah

Capacity shows how much energy the battery delivers before it is fully discharged. The figure is set by the carmaker and it is not arbitrary: the alternator is sized for a specific amount of charge. Going 5–10 Ah above the factory value is fine if the dimensions match, but a noticeably larger battery simply will not recharge in city driving.

A smaller capacity has the opposite effect: in winter, on short trips, the battery slips into chronic undercharge, which leads straight to plate sulphation.

2. Cranking amps, A (EN)

This is the current the battery delivers to the starter in the first seconds. The colder the climate and the larger the engine, the more amps you need. For Kazakhstan the rule is simple: never go below the factory figure, and a reserve is better.

3. Terminal layout

Polarity is about which side the positive terminal sits on. Get it wrong and the cables will not reach. It is described as standard or reversed, and in Asian sizes by the letters L and R at the end of the code.

4. Dimensions and case type

Length, width and height must match the tray. On Asian cars the case is coded as B24, D23, L2 and so on — these are standardised sizes, and choosing by them is easier than by millimetres.

5. Technology

A conventional calcium battery suits most cars. Vehicles with a start-stop system need EFB or AGM: they are designed for hundreds of extra starts per trip. You can fit a conventional battery to a start-stop car, but its life will be cut several times over.

Where to find these numbers

• on the battery already in the car — capacity, current and case size are all printed on it;
• in the vehicle owner's manual;
• through selection by make and model in the catalogue — we have collected the factory requirements into one table.

If in doubt, photograph the label on your old battery and show it to a consultant at any centre of the network. Selection, installation and trade-in of the old battery are included in the price of the new one.

Related: how many cranking amps your car needs and how not to get polarity and case size wrong.