Car is a 1985 W126 500SEL that I installed the 5.6 ECE Euro V8 into a few years back.

Before I go crazy trying to figure this out, maybe someone can give me a second opinion.

I recently did the 'Saab' aternator upgrade, because I'm running alot more electrical equipment, electric fans, electric waterpump, modern sound/media installation etc. I used the alternator from a late model 9-5, and its got a 130A rating.

My battery is a Bosch Silver, and is the correct size for the car (it fills the battery tray) but is about 3 1/2 years old.

In the cold weather we have been having recently here, the outside temps havent been much above freezing. The car is sluggish to turn over after its been sat for anything over several hours, and i'm frightened that its going to leave me stranded somewhere.

Battery measures 12.5v with car off.
At cranking, battery measures around 10.2v
Once started, the battery measures 14.3v or so.
I checked for equipment draining the battery when the engine is off, and its around 20-30ma, so thats ok.

I've googled about how long these Bosch batteries should last, and most people reckon longer than the 3.5 years that i've had mine for.

Any suggestions welcome

Ben.