I have a 2008 Mini Cooper base and the other day I had the battery light come on. Two days later, before I could look into it, the car lost battery power on the highway, no interior lights, no radio, no power steering. I pulled off the road and into a parking lot and muscled the steering into a stall but left it running because I felt it wouldn’t start if I turned it off. Shortly thereafter however, it started to misfire so I killed it. It wouldn’t start up again, just as I expected. The next day I walked a few miles to it to see if I could see a problem, but it actually started. I made it the few miles home before it did the same powerless things. I had the battery tested and they said it was fine, so I replaced the alternator. But the problem persisted so I have it sidelined while I try to find the problem. Anyone know what else it could be or what else to look for?

 

Hello,
I have a 2009 MCS. When large red battery icon displayed on mine, it was my understanding that charging system (i.e.. alternator was inoperative) and car was just running on batery power. I turned off all electrical accessories (radio, hvac) and was able to drive 20 miles on battery to male it home. I had a scangaugeII on car and could watch battery voltage slowly decrease from 11.9v to 10.6v when I arrived home.

I replaced existing OE 120amp alternator with oem valeo 120 alternator and life was good again. Its important that you confirm replacement alternator is correct one. Its my understanding that cars either have a 120amp or 150amp alternator.

Hope above helps, good luck,

W

 

Get yourself a digital multimeter and measure voltages.

Measure voltage at the battery with the engine running.

Measure voltage at the battery after the car has been off for several hours.

Post those voltages here. That won't tell us everything but it can tell us a lot.