I just installed an Alta CAI and removed negative side of battery. When done, I reinstalled the cable and turn on the car and got the excessive battery discharge warning light. Checked everything and it's all where it should be. Left the car with an 18hr slow charge and battery is fully charged and show the green sign on the battery itself but the warning light still comes on everytime I turn on the engine. Any clues???

I have no dealership in my town, leave in brasil and it's hard to find tech support here for this car. Any help appreciated...

 

check the battery cables

could be as simple as a loose connection

 

I already checked and it's all in the right place. I just unplugged the negative side and after install plugged back on. No rocket science there... I think these cars are so sensitive for everything. My friend that works at BMW now advised never to unplug battery on these cars and it could a bunch of different issues. And for me is not as easy as you guys to drive 20 miles to a dealer. Closest dealer is 2000 miles away... Not a chance. any other suggestions? Is there anyway to reset that light?

 

maybe try removing both cables and then connecting again. When I installed my Alta CAI, I removed both just to be safe, then connected both at the end.

 

Normally disconnecting the battery "resets" the ecu. I know this may sound crazy but maybe your alternator is on its way out and since it was a gradual process the ecu "learned" that it wasnt providing the same charge as when it was new, and now that the ecu is back to the stock parameters it noticed that its not getting the same charge as it thinks it should and this is causing it to throw a light.

Now you can tell me I'm crazy, I wouldn't take offense, but somehow this crazy idea of mine makes some sort of "what if" sense to me...

 

How about looking at the hood....maybe you bumped something...a switch, or wire, and an underhood light is staying on....
Perhaps the warning is unrelated! Crazy things have happened....knew a mechanic once, told ne he changed the oil on a minivan....caught fire 2 miles later...was unrelated. Crap happens.

 

Hate to say it, but MINI batteries are fail. I've replaced more then what I consider a fair share. I bet you have a bad cell. If you have a local shop (doesn't even have to be BMW/MINI) that has a Midtronics (or any brand) Battery and Electrical system tester I would have them run a test on it, or if you have a DVOM you could do your own voltage test on the electrical system. Like I said earlier, I bet its your battery regardless of how long or how many miles you have on your JCW. I've seen cars (2012's) with less then 1500 miles come back with batteries that have taken a complete dump. The alternators not so much (solid for most part @ early life).

Oh and whoever told you that you shouldn't disconnect the - terminal/connection when doing anything related to removing sensors or working on these cars you should stop taking their advice. Yes you can get away with allot of service and repairs leaving the battery connected, but a good rule of thumb is "why risk it". Also disconnecting the - terminal will not reset anything DME wise or how your car will function in terms of learned values.