I agree with Loius - one or more cells went dry and that's that - it's gone.

I haven't seen a self-maintainable auto battery in years, but that's how it is in the U. S.

12 volt batteries contain 6 cells and the ideal charge in each is 2.1 volts. 6 x 2.1 = 12.6 volts - the ideal reading one would get with a VOM set on the 20 scale and after the auto had been at rest for 6-8 hours.

If you cancel out one cell(2.1 volts), and the other 5 are healthy(2.1 volts each), you're down to 10.5 volts. That won't work. In all likelyhood if one cell is dry the others are probably below optimum.

Time for a new battery.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"