Actually... maybe my battery still is OK, even after 9 years. I am charging it right now with my trickle charger battery tender. It puts out a whopping 1 Amp 12 volts so it takes forever. I might just be underestimating exactly how long it should take. I had it set for the last month to run 2 hours/day. I guess that just wasn't enough.

Multimeter reading just read 11.35V, gunna leave it on for a while and see if it increases closer to 13V and holds the charge at all.

My other car is reading 12.32V and starts fine. But I also had a new scion not long ago and I remember that one reading > 13V.

Well after another 12 hours of charging it's still at ~11.35V :( Guess I am gonna try to charge it again tonight for another 12 hours but I doubt it's gonna do any good. I'll probably start getting the back gutted so I can pickup the Bosch battery tomorrow and drop it in.

I guess you are supposed to let the battery sit for a few hours for testing voltage so I will check it again when i get home, still not very optimistic here.

I actually went Optima blue-top (marine 12volt). I did have to build custom brackets and due to the extra height had to dump the spare tire. That's not a problem for me since I drive mainly local, but I always throw a spare in the cargo area for cross-country trips just in case. I also run alot of electrical accessories and additionally have a 3000w power inverter which connects nicely to the "extra" posts on the blue-top model. I've been very pleased with Optima...

Dang, how much is that beast? I measured my voltage when i got home, a dissapointing 10.65V - pretty sure it's done for. I'm not sure if this is the normalized voltage after letting the batt sit for a while after charging (i was thinking it would increase) or if the car was actually drawing significant power from the battery during the 9 hours i was gone.

one thing i noticed is that if i volt test right after i take the the charger off - it reads 11.6V+ but then pretty rapidly drops to 11.35V, holds steady and then again drops over time.

Would driving the car and charging off the alternator provide any advantage over the trickle charger?

Old battery just isn't cutting it. It will barely start the car, but usually not on the first attempt and I have to wait about 30 seconds for all the startup shit drawing current to finish. So the hell with it.

I bought the last Bosch 49 they had at the local Pep Boys store. I didn't realize they give you $5 back for the old battery. Will be $108 total when all said and done.

I think I paid around $210 or so for the Optima Blue-Top. The nice thing about a marine battery of course is that fully draining the battery (e.g. letting the car sit for weeks at an airport) won't permanently impair it like a regular battery and it just takes an average drive or two to fully recharge it to like-new condition. It's well worth the piece of mind in my opinion....

I went with the bosch for $108 bones. Dropped right in, works great.

Multimeter reads about 12.5V engine off, 14V engine on. BMW Diagnostics Menu reads ~13.7V and no problems with codes.

I put a little dialectric grease on the terminals since the old batt had a tiny bit of corrosion on it (amazing since battery is INSIDE the vehicle).

Hey this is great info. How do you access the BMW Diagnostics Menu to read the battery voltage?