The short answer
Fit the new battery, connect the tool and go into the BMS or "battery" function. If the new one is identical to the old one, choose to register the change. If you are changing capacity or type (from EFB to AGM, for example), choose the coding option and enter the details from the label. When it is done, clear the faults and check that stop-start works again.
Many modern cars, especially those with stop-start, have a sensor on the negative terminal that monitors the battery. The control unit uses that data and the battery's age to decide how much to charge it. With a new battery that hasn't been registered, it keeps applying the strategy for a worn one: it overcharges it and shortens its life.
Which cars need it
It is common on BMW and Mini, the Volkswagen group (VW, Audi, SEAT, Skoda), Mercedes, Volvo, Ford and many recent models from other makes with stop-start. A quick clue: if the battery is AGM or EFB and has a sensor with a lead on the negative terminal, your car almost certainly needs it.
| Situation | What to do with the tool |
|---|---|
| New battery identical to the original | Register the battery change |
| You are changing the capacity (Ah) | Code the new capacity and register |
| You are changing the type (EFB to AGM, for example) | Code the type and capacity, and register |
| You have only charged or disconnected the battery | Don't register. Clear any faults that have been left |
Step by step
- Note down the new battery's details: type (AGM, EFB, lead-acid), capacity in Ah and, if the tool asks for it, the serial number or manufacturer.
- Swap it in the usual order: disconnect the negative first and, when refitting, connect the negative last. If you can, use a memory saver so you don't lose the radio and window settings.
- Connect the tool, turn the ignition on and identify the car.
- Go into Service → BMS (or the power management control unit, depending on the make).
- Choose the option from the table above: register, or code and register.
- Enter the details if asked and confirm.
- Read and clear faults across the whole car: it is normal for the swap to leave low-voltage codes in several control units.
- Initialise anything that needs it: electric windows, sunroof or the steering position, depending on the car.
Stop-start may take a while to come back. After registering, the car usually needs a few days of normal use before it reactivates stop-start. It isn't a fault: it is measuring the new battery.
What happens if you don't register it?
The car runs, but the new battery is charged at a voltage meant for a worn one. In the long run it fails early, stop-start may misbehave and battery warnings may appear on the dash. Given what an AGM battery costs, those two minutes are well spent.
If you are not sure whether the problem is the battery or the alternator, check the voltage in live data: with the engine running it should be roughly between 13.8 and 14.7 V.
Which iCarsoft tools register the battery
The BMS function is on the current multi-brand tools (CR Pro, CR Pro+, CR Max P, CR Ultra) and the V2.0 single-brand tools, such as the BMM V2.0 for BMW and Mini or the VAWS V2.0 for the Volkswagen group. The V1.0 range does not include it. On BMWs it is also one of the most used functions; if you have one, take a look at BMW and Mini diagnostic tools.
