Battery ratings explained
What the numbers and letters on a battery mean – and which ones matter for your car.
The numbers on the label
Almost every car is 12 V. Trucks and buses often use two batteries for 24 V.
How much energy the battery stores, measured over 20 hours. More Ah means it runs your electronics longer while the engine is off.
Starting power – how much current a fully charged battery can deliver at −18 °C. Higher is stronger.
Minutes a full battery can supply 25 A on its own – think lights, wipers and ignition at night if the alternator fails.
SMF, EFB (stop/start) or AGM. See below.
Compare like with like. Cranking power is measured under different standards – SANS, EN, SAE, DIN and IEC. The tests differ – SANS measures for 60 seconds, SAE for 30 – so the same battery shows different numbers. Only compare numbers from the same standard.
Battery types
The everyday car battery. Sealed, so there's no water to top up.
Shop SMF batteries →For cars with stop/start. Handles far more starts and runs the car's electrics while the engine is off at a stop. Replacing one
Shop stop/start batteries →Spill-proof, with strong starting power. For premium stop/start, mild hybrids and cars with lots of electronics.
Shop AGM batteries →Built for trucks, buses and tractors. Many use two 12 V batteries together for 24 V.
Shop truck batteries →For caravans, boats, camping and backup power – made for slow, deep use, not for starting a car. Dual battery setups
Shop leisure & stand-by →For motorbikes, scooters and quad bikes.
Shop motorcycle batteries →Choosing the right one
Check these four things on your old battery, or ask us.
Stop/start cars need EFB or AGM. Never go down to a standard battery. Why it matters
At least the same Ah and CCA as the original. More is fine – less isn't.
It must fit the tray, and the hold-down must clamp it firmly.
Right-hand or left-hand positive – see below.
Right-hand or left-hand positive?
Batteries of the same size come with the posts either way round. The wrong one means the cables won't reach.
- Stand in front of the battery with the posts closest to you.
- + on your right = right-hand positive.
- + on your left = left-hand positive.
Also check the posts: the + post is slightly thicker than the −, and some Asian cars use thinner posts.
- Don't stretch or force the cables to reach the wrong post layout.
- Don't go by the old battery alone – if it wasn't the original, it may be the wrong type.
- Don't use a car battery for solar or inverters – it's not made for it, and the warranty won't cover it.
Extras count. Big sound systems, extra lights and trackers need more capacity – go up in Ah. Running a fridge or camping gear? Add a second battery.
Not sure which battery?
Pick the easiest way – we'll make sure you get the right one.
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✓ Free battery test in-store