Every time I go to start my 06 base cooper, everything goes completely dead, dash lights, headlights, Dome light etc. So I have to remove the battery wires and put them back on every time I go to start the car. I’ve tried parking my car taking off the wires and then putting them back on after I’m gone from the vehicle for a while and that doesn’t help so there is no draw on the battery when the car is off. Bump starting the car still works most of the time, sometimes after I re connect the battery to get my lights all back on a failed start if I go to bump it everything goes dead other times it bumps perfectly fine. I tested my battery to some 12 volts when the car was off and to some 13.85 with the car running and all the fans on as well as lights. Please help with this diagnosis!!

 

first thought is bad battery ..... these lil beasts get very flaky when the battery starts to go. If you don't want to buy one ... try swapping with a battery you KNOW is good. If the battery in the car is four years or older ..... You don't mention JUMPing ..... and YES I've had MINI battery TEST perfect but LO a new battery SOLVED all my problems.

Unlike my 79 and your older cars, when you hit the START in a MINI (or most any car today) you are not simply closing the circuit from the battery to the starter causing it to CRANK (which is when you'd hear a slow crank or signs of a weak battery) TODAY all you do is send a msg to the computer ASKING IT to start the car. The computer then does a bunch of checks and decides IF it will initiate a start sequence. Unplugging the battery and trying again CAN POSSIBLY cause JUST ENUF change ...... NOT uncommon for the car to start fine then 5 minutes later NUTHIN (and NOT unique to MINI ... in the past couple of years have had same thing on a 07 Honda FIT and a 14 Focus ST)

p.s. While I TOO have done it ... bump starting today's computer heavy cars IS risky. You can send a surge into the electrics and cook expensive parts.

 

^ this, the Capt speaks wisely. Most likely the battery.