Advice · updated 2026-10-03
Stop-start battery replacement explained
Stop-start needs an EFB or an AGM so the car can restart all day. A basic flooded battery is the wrong part. We'll fit the right type at the car in London, Birmingham or Manchester.
What the system is using the battery for
Each time the engine stops at a light, the battery runs the car and then accepts a restart. That is cycling, all day, on top of ordinary starting. A flooded battery made for a single start and a long run is not built for that pattern.
EFB covers many entry systems. AGM covers heavier ones and a lot of cars that also recover energy as they slow. Read the label. Do not swap the names because they both say stop-start on the box of a retail battery.
The earth-lead sensor
Many of these cars have a sensor on the negative terminal. It measures current so the car can decide whether stop-start is allowed. The sensor stays intact. A universal clamp that bypasses it leaves the car guessing.
Registration is how the car is told the battery is new. It is commonly required on Volkswagen Group and many BMW and Mini models and varies on other marques. Without it, stop-start can stay off even after a correct battery is fitted.
What a proper replacement includes
The fitter comes to the parked car, fits EFB or AGM as agreed, refits the hold-down, and registers when required. Resting voltage on a healthy 12V battery is around 12.6V. Running charge is often about 13.8 to 14.7V, with smart charging able to sit lower once the battery is reported full.
The alternator is not a bulk charger. Replacing the battery is the repair when the unit is finished. Type your mobile number on the quote form. We call you back. Cover is London, Birmingham and Manchester.
Questions before you send a quote
Will any stop-start battery do?
No. Match EFB or AGM to the car. AGM is not downgraded to EFB.
Why is stop-start still off after a new battery?
The type may be wrong, or the battery may not have been registered on a car that needs it.
Do you do this at the car?
Yes. We'll come to the car. Start with the quote form.
A worked example
A 2016 hatchback cuts the engine at every light and restarts as the clutch comes up. The label says EFB. A flooded battery was fitted last year and stop-start has not worked since. The repair is an EFB, or an AGM upgrade if agreed, plus registration if that model stores battery type.
Safety
Do not jump a cracked, leaking, swollen or frozen battery to test whether stop-start returns. It will not, and the case is unsafe to connect.