A Stop-Start car switches the engine off at every set of lights and restarts it when you lift off the brake. In city driving that's dozens of engine starts on a single trip, and every one of them comes out of the battery while the alternator isn't turning. An ordinary flooded battery is built for maybe half a dozen starts a day. The maths doesn't work.
EFB and AGM: the two correct answers
EFB — Enhanced Flooded Battery — is a reinforced flooded design built for roughly three times the cycling of a standard battery. It's the usual factory fitment on entry and mid-range Stop-Start cars.
AGM — Absorbed Glass Mat — holds the electrolyte in a glass fibre mat rather than as free liquid. It cycles harder again, tolerates deeper discharge and is sealed. It's the factory fitment on cars with heavier electrical loads: regenerative braking, electric power steering, a lot of driver-assistance electronics.
A car specified for EFB can take an AGM. A car specified for AGM must not be given an EFB or a standard battery — the charging profile is different and the battery will not survive. If you're not sure which yours takes, we check before we fit.
Why the new battery has to be registered
Most Stop-Start cars run a battery management system that tracks the age and state of health of the battery and adjusts charging accordingly. It does not notice that you've fitted a new one. Unless the replacement is registered to the BMS, the car keeps charging as though the battery were four years old — which either overcharges a new battery or undercharges it, and in both cases shortens its life considerably.
- 1Confirm whether the car wants EFB or AGM — not a guess, a check
- 2Fit the correct type and case size
- 3Register the new battery to the BMS
- 4Verify the charging voltage before we leave
Registration is included in our number. Some places charge it separately, or skip it — which is why a battery that should last five years sometimes lasts two. See the Stop-Start range or the AGM range for what we carry.
Common questions
How do I know if my car has Stop-Start?
The engine switches itself off when you come to a stop and restarts when you lift off the brake. There's usually a dash button with an A inside a circular arrow to disable it. If you're not sure, tell us the make, model and year and we'll tell you.
What happens if a standard battery is fitted to a Stop-Start car?
It generally lasts somewhere between six and eighteen months instead of four or five years. The Stop-Start function often disables itself first as the battery's state of health drops, which is the car protecting itself — and a useful early warning that the wrong battery is fitted.
Do you register the battery to the car?
Yes, and it's included in the price rather than added afterwards. We verify the charging voltage before we leave.