Discharged battery in MINI Cooper – how to fix it?

Driver’s question about a discharged battery in a MINI Cooper

My problem is a discharged battery in a Mini Cooper S. I bought the car used in 2017, from a BMW dealership. I do not know its service history. Less than 2 years after purchase, I have a problem with the battery.

In December 2022, with heavy snowfall, I did not start the car for several days and then the first battery discharge occurred on its own. The battery discharged to zero. After that, I had to make up miles to recharge it, and every day after that, I had to make sure not to use lights, etc. things that would overcharge the battery. I should add that I didn’t do big routes. Only 10 km twice a day, driving mostly in the city. I was on vacation last year and everything was fine. Once a month I did a route of 300 km in one day.

Along with the discharged battery, there was a problem with the driver side window closing. Only after charging the battery to full would the window close all the way, with the other window there was no problem.

Service actions to date

In January, I took the battery to a charger because it had discharged to zero again. We charged it to full and the car even started differently. Unfortunately, again after one day in the garage the car did not start, the battery died again. After the roadside assistance charged the battery again, I decided to do a computer diagnostic and out came the ZGM (Central Gateway Module) error, which is responsible for putting the car to sleep completely. This is apparently the problem here, because I turn off the car with the remote control, while the car does not go to sleep, and as a result the battery is discharged.

Probably to be replaced is this controller. Please give me a hint. Is the fault on the side of the controller? Alternatively, could it be the doors that do not close all the way? Or, is it likely that this fault was before and does it appear in other cars? Can I report this as a hidden defect at the dealership where I bought the car?

The problem affected a 2017 F55 MINI Cooper S, but it may also occur in other models.

BM Cars service answer: how to remedy a discharged battery in a MINI Cooper

The problem of a rapidly discharging battery is a complex one. There are many factors that can cause this effect. The main issue is the condition of the battery and its technical condition. The maximum life of AGM batteries is usually 5 years. If the battery in your car has not been replaced, its condition even with proper operation and charging will require replacement.

Another factor that affects the condition of the battery is its charging and discharging rate. With a properly functioning alternator and maximum current consumption, the charging voltage at idle should not drop below 14.2 volts. To be able to charge the battery sufficiently, it is also necessary to keep the engine running for more than 20-30 minutes. Short driving distances, frequent extinguishing and starting it, as well as a heavy load in winter (seat heating, rear window, blower, radio, etc.) cause additional current consumption and, as a result, undercharging of the battery.

With a well-functioning charging system and a functioning battery, the car goes into sleep mode after closing (after about 30 minutes) and current draws decrease to about 0.01 A. In such a state, the car can stand for up to several weeks, and after reopening it should allow the engine to start without a problem.

What to do when the battery has been completely discharged?

If the battery has already been completely or very deeply discharged, the car then loses its stored functions, including the initialization of the electric windows, the memory of the seats (in the electric version), the deletion of the clock and date indications, and sometimes the deletion of stored radio stations and audio settings.

Once the faults are cleared and the battery is recharged or replaced, it is necessary to reinitialize the windows and set individual vehicle functions.

An additional element that causes frequent battery drain problems is the failure of the vehicle to go to sleep at a standstill. This can be caused by a malfunction in the body controller or other controllers (e.g., transmission, engine, audio system), which causes the car to wake up cyclically and prepare it for starting. Current draws of up to 1-3 amps, which occur then, will cause even a new battery to be discharged within a day.

We suggest following these steps to remedy your MINI’s battery discharge problem

1. Complete computer diagnostics of the vehicle with special attention to vehicle energy management, charging voltage.
2. Checking the condition of the battery (possible replacement and re-registration of the battery).
3. Checking resting current draws, finding the source of vehicle wake-up.

As for warranty issues, the factory warranty is for a period of 2 years from the date of first registration of the battery. The problem with battery discharge or excessive draws cannot be a latent defect, as the vehicle has been in service since 2017.

In order to carry out the ordered work, we invite you to schedule an appointment with our service center.

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