How to Choose a Car Battery: AGM, EFB or Standard
A practical, five-step check for matching a replacement car battery to the vehicle: technology, size, capacity, cranking current and terminal layout.
Identify the technology
Check whether the vehicle has start-stop. Start-stop vehicles need an AGM or EFB battery. Vehicles without it usually use a standard flooded battery.
Pro tip: Never replace an AGM battery with a standard one: it will fail early in a start-stop vehicle.
Match the physical size
Measure the battery tray and compare length, width and height with the product dimensions. The case style, such as L2 or L3, indicates the footprint.
Pro tip: Check the hold-down clamp will still seat correctly.
Check capacity and cranking current
Match or slightly exceed the original Ah and A ratings. A higher cranking rating is helpful in cold climates; lower is not advisable.
Confirm the terminal layout
Look at which side the positive terminal is on. A mirrored layout may not reach the cables, and a stretched cable is a safety risk.
Pro tip: Photograph the old battery before disconnecting it.
Fit and register
Many modern vehicles need the new battery registered with the battery management system. Follow the manufacturer's procedure, and recycle the old battery.
Related questions
How do I choose between AGM, EFB and standard batteries?
Vehicles with start-stop systems normally need an AGM or EFB battery, while older vehicles without start-stop usually use a standard flooded battery. Check the vehicle handbook and read our buying guide for a step-by-step check.
What do the Ah and A numbers mean?
Ah is the capacity: how much energy the battery stores. The A figure is the cold cranking current: how much power it can deliver to start the engine. Match or slightly exceed the original specification, and make sure the terminal layout and dimensions fit.
Can I fit a higher-capacity battery than the original?
Often yes, provided it physically fits the tray, has the right terminal position and is the same technology. Fitting a lower specification, or swapping AGM for standard in a start-stop vehicle, is not recommended.