Battery No Longer Powerful

Normally my Z4 stays in the garage until the weekend. Then I started driving it every day to the P.O. and back (10 mrt). Then one day it didn't start. I took the battery to the parts store and they checked it out for an hour. It was O.K. Then I contacted the BWM shop and took it in. Again it checked out O.K. The mechanic asked about my driving habits. He said I had a bad driving profile. The battery would be drained a little during non-use and more upon start-up. I was not driving far enough to charge it back up. He said he has had this discussion with people who buy a new 7 Series and come back a month or two later complaining about a dead battery. Anyway, I bought a trickle charger for $70. I connect it and it "tops off" the battery every 2-3 days.

Measure the battery voltage with the engine idling. Measure the battery voltage with the engine and everything on the car turned off. Post the numbers here.

--scott

Never mind the battery - it kills an engine never getting to full working temperature. Which it won't in five minutes regardless of what the temp gauge says.

I have a charger bought from Lidl for 12 GBP. Charges the battery then switches to a maintenance charge which can be left on indefinitely. Small enough to just about fit in the pocket, but powerful enough to charge a flat battery overnight. Very handy for my other car which doesn't get as much use as my BMW.