So I have a base 57. It's a 07 cooper base with a push button start auto trans. Wife drove to work, 8hrs later put fob in no light, nothing..... after several jump attempts got it going and home. Now it died again. Put brand new battery in still nothing. While I put fob in everything lights up, I can hear the relay kick on and when I push start all I get is one click and nothing. Switched starter out with known good one and same issue. 1 click. Battery is 12.6 v I put the starter on a stand alone battery and it seems good spins and soliniod pushes plunger out then spins. So I don't know what else it could be. Any advice????

 

Voltage is only one aspect of the battery's power. You need to find out how many amps (cold-cranking amps, or CCAs) it's producing. The fact that you were able to get it running by jumping indicates the new battery may not be producing sufficient CCAs. Get the new battery tested first.

 

Old battery showed 1 bad cell so got a new one. Cold crank amps 650 out the gate. I didn't check old one. But both batteries have done the same 1 click . Also I was able to puta socket to the cranckcase and turn it freely so I know the motor isn't ceased.... I didn't think it would be but thought I would check.