I posted most of this on another thread. However, while playing with my new toys, I decided this probably deserved its own thread.
A couple weeks ago I watched three videos from Kent at MercedesSource concerning battery life, charging, testing and reconditioning.
I was so impressed with the videos that I upgraded my equipment.
My old charger served me well for the last 35-40 years and still works fine. It was probably as heavy as any non-wheeled charger you could get when I bought it, weighing perhaps 35# and capable of starting a vehicle/tractor with a completely dead battery. For testing I had a battery hydrometer and a load tester. However, times and technology have changed.
Kent was using a Ctek US 7002 charger/reconditioner/maintainer and a Solar BA-7 battery tester.
I shopped for smart chargers, narrowing it down to the Genius and Ctek lines, eventually deciding to spend the additional $30 to get a Ctek MUS 4.3, and for a tester, I stuck with the Solar brand and found a bargain on a BA-9.
Part of my reasoning in buying the new equipment was discussion in the videos of the squirrely behavior of newer cars with batteries which no longer meet specs. I was having odd behavior from my 129 and though neither of my SLs failed to turn over and start I thought it worthwhile.
By yesterday, I had both pieces of equipment and began playing with them.
My Silverado, with its two year old battery, tested good as I expected. It was nice to have a baseline to "test the tester".
The results on the SLs were not so positive. I began by charging and reconditioning the battery in my SL500, after which, it showed bad. As for my 380SL, on testing it said I should charge and retest, which I'm in the process of doing, but I expect it to fail as well.
One of Kent's conclusions concerning battery life was that perhaps we should consider replacing batteries when they reach 4 years old. I suspected the battery in my Silverado was on its last legs 6 months before it failed. Had I been able to test it properly, I might have avoided the inconvenience.
After saying all of that, perhaps I should let the other shoe drop.
I bought the 380SL in 2008 with a new battery and my SL500 in 2010 with a battery of unknown age... and I've never replaced either of them!
I suppose you could say that they were both past due and both cars will be getting new batteries!