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AGM, EFB and standard flooded batteries are not grades of the same product. They are different constructions with different charging behaviour. Fitting the wrong one can shorten its life, even if it starts the car on day one.
The right choice is the specification the vehicle was built for — not the most expensive battery on the shelf.
The three types in plain language
Standard flooded battery
This is the traditional lead-acid battery with liquid electrolyte. It is the usual choice for older cars without start-stop.
A maintenance-free battery is not a fourth chemistry. It is a sealed construction within the flooded or AGM family. The car still specifies a group size and a technology.
EFB battery
EFB stands for Enhanced Flooded Battery. It is designed for repeated engine restarts and is commonly used on start-stop cars.
EFB is not the same as AGM. It is a different construction, and it is not automatically an upgrade or a downgrade. It is the specification some vehicles require.
AGM battery
AGM stands for Absorbent Glass Mat. The electrolyte is held in a glass-mat separator, which makes the battery more resistant to vibration and better suited to repeated cycling and higher electrical loads.
AGM is common on start-stop cars, vehicles with higher electrical demand and some European models. It is not a universal upgrade: a car that specifies EFB should not be given AGM just because AGM costs more.
Why the wrong type causes problems
Modern cars control charging. The alternator, battery sensor and engine management expect a particular battery behaviour. If the construction does not match the vehicle’s charging strategy, the battery can be undercharged, overcharged or cycled in a way it was not designed for.
The result is usually not an immediate failure. It is a battery that does not last as long as it should, or a start-stop system that stops working correctly.
What actually decides the battery
Four things matter before you buy:
- Group size and case shape. The battery must fit the tray, hold-down and terminal layout.
- Capacity and cold-cranking rating. The vehicle needs enough reserve and cranking power for its engine and electrical load.
- Technology. Standard flooded, EFB or AGM, as specified by the vehicle.
- Registration or coding. Some modern cars need the new battery registered with the charging system. Not every car does; the quote should say whether it is required.
A battery label on the old unit is the best starting point. It usually shows the group, capacity and type that the factory fitted.
“Can I upgrade to AGM?”
Only if the vehicle’s charging system is designed for it, or the manufacturer lists it as an acceptable option. A higher-capacity battery that does not match the group or charging strategy is not automatically better.
If your car has start-stop, do not replace an AGM or EFB battery with a standard flooded unit to save money. It will fit, but it is the wrong part for the charging system.
What we check before quoting
- the old battery label: group, capacity, CCA and technology
- whether the car has start-stop
- the charging output and battery condition
- the hold-down, terminal layout and access
- whether the vehicle needs the new battery registered
We confirm the exact battery and price in writing before dispatch. We do not publish a fake “from” price, because the correct unit depends on the car. If your car needs a new one, the replacement is done at your car, matched to the specification above.
The short answer
- Older car without start-stop: standard flooded is usually the starting point.
- Start-stop car specifying EFB: use EFB.
- Start-stop or high-load car specifying AGM: use AGM.
- Maintenance-free: a construction feature, not a separate chemistry.
If you are not sure, send the car’s make, model and year, plus a photo of the battery label. We will confirm the specification before anything is supplied.
