UPDATE:

I am driving the BMW this week. I pulled the battery out of the 300SDL and have been charging it with a trickle charger for two days now. I charged it for 6 hours on Sunday. It went to 13.04 Volts and then on Monday it settled at 12.5 volts. I charged it Monday for 6 hours and it went to 13.1 volts and I could hear it " cooking". I unplugged and this morning it was still at 12.5 volts. I will let it sit all day then charge it again tonite. I know it would be a whole lot easier to just go buy a new battery, but I do not need the car this week and I want to play with the battery and charger. I am going to do this till Friday night and then re-install it on Saturday and see if it works.
If it does not work, Saturday it is new battery day.

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John
1986 300sdl
1985 380se