I'm new to this forum as I just bought my first 07 Cooper S. I've noticed that my Cooper's battery will run flat after a few minutes if I use the radio, or use a small cig lighter car vacuum. I mean less than 5 minutes. I thought batteries lasted at least an hour or so when you use the radio on accessory. I recently installed a new pioneer in the car and the clock in the new radio resets itself after about 30 minutes, after car is off for 30 minutes to overnight. Radio stations are lost too. Could a bad battery be the culprit? I'm still able to turn the car on every morning, I'm just careful not to leave anything on in the car for longer than 5 minutes or battery dies. Thanks for the help or suggestions.

 

Please define "battery will run flat". If it is able to start the car, it can't be that "flat". Does the car's clock reset, too?

How old is the battery? Have you checked the wiring of the stereo? What wire gauge did you use for the ground and power wires to it and how long are they? I once had an aftermarket radio reset every time a 2.4 liter diesel engine was started due to the onboard voltage dropping below what the radio needed to function properly. Using a shorter and thicker ground wire solved it.

FWIW:
Don't know if it was the case with pre-facelift models, but my 2010 LCI shows a warning message if it senses that the battery has reached a low charge level. It also switches off secondary accessories in order to preserve battery power for the ignition.

Edit: corrected year of my car (2010, not 2020)

 

take the new radio out of the equation by pulling fuse and see if the problem continues .... if it goes away you have your source

MINI in general does not like 'marginal' batteries. My 15 was getting a lil wonky, throwing service alerts at random, but no actual service tracker active ... no codes recorded. Battery 'tested good' BUT having been an owner since 2002 and knowing the battery was 5 years old I replaced it and guess what? Problem gone . . .

 

One little thing to do that will be appreciated by your battery is to hit 'lock' whenever you park. Unlocked, there are always background devices turned on that are sucking power.