Replacing battery
 

Need some quick info on this as the '03 E46 Touring's battery apparently just gave up the ghost after 5 1/2 years.

Does anybody know if a certain amount of voltage has to be maintained on the electrical system during a battery change? I didn't see anything in the maintenance manual and I'd hate to dork up something like the OBC, which would probably require a trip to the dealer for re-programming.

You should be OK... OBC memory will be lost (no different that resetting the mpg, avg speed and trip ODO), but otherwise no problems. You'll have to reset the clock too...

I've disconnected the battery in both the E46 and the E39 many times with no issues, and did a battery swap in the MINI myself. A battery swap isn't any different that disconnecting and reconnecting the existing battery...

There are no codes needed or anything. Just pull and replace.

Cool. Thanks. It's off to Interstate Batteries then. They quoted $154 for a new one. Might be a bit on the upside, but I won't skimp when it comes to a good juicer.

Happy ending
 

After placing the new battery in and hooking everything together (no leftover parts on this DIY this time) it cranked on the first try. I was a little suspicious at first that it could possibly still be the alternator, but they were put to rest when it turned over without a problem.

Like ZBB said the OBC memory was lost, but other than interesting tidbits oh history that were lost, big deal.

Easiest DIY to date.

I feel pretty fortunate to have extracted 5 1/2 years out of the original battery, as I recall having to replace the one in the E36 after only 4 years.

Who says BMW's aren't getting more reliable?

If that were a fear of mine, I wouldn't put it to rest just because a fresh battery cranked and started the car.

But that's just me.

Alex

If that were a fear of mine, I wouldn't put it to rest just because a fresh battery cranked and started the car.

But that's just me, and at 5 1/2 years why are you suspecting the alternator?

Alex

Climate has a big impact on batteries... We're lucky to get 3 summers out of them here (they never die during the beautiful months we call winter).

My E46 had its battery die within a month of moving back to AZ -- the car was about 3 1/4 years at the time. It was mid Sept -- and probably ~105 or so high that day. The MINI battery lasted a little over 4 years -- and it also died on a hot Sept day...

Only because I called my indy mechanic and asked him what else besides the battery could be the root of the problem. He stated the other culprit could be the alternator.

When I noticed the problem Saturday morning I jumped the battery and then drove it around letting it charge for about 30 minutes. After a 30 minute rest I tried to crank it again and it wouldn't turn over.

I reckoned the easiest thing to fix was the battery. Maybe I could have had it tested and milk it for another year or so if it passed, but I figured why gamble when it's on borrowed time anyway.

But going back to the alternator? Are they any tell tale signs when an alternator is about to crap out?

Come to think of it the battery on the E36 croaked on an extremely cold day (minus 15). I guess extreme temperatures can be the death of a battery.