Proactive battery replacement on W221?
The guys at Sears put their meter on it and told me that while it's low on the CCA's, it's within spec and so doesn't "need" to be replaced today.
Nevertheless, I'm toying with the idea of just paying the $175 now for a DieHard AGM, since a) it'll have to be replaced at some point anyway, and b) I'd rather replace it on my own terms, as opposed to the time and place of the battery's own choosing.
I'm curious how long we (as a community) should really expect the OEM batteries to last on these cars when driven in the heat of southern CA and NV?
Your thoughts and personal experiences are warmly welcomed!
Batteries last a long time if you keep them charged up at all times.
12.4V is the magic number, though you may not see that when you open the doors to check, as lots of things switch on and drag the voltage down.
Edit: Agree with others that they don't last long in the heat, though.
Nick
Last edited by Welwynnick; Sep 23, 2017 at 03:50 AM.








So, 5 year 90K mi Texas run on an OEM battery. Below freezing in the winter and +100 in the summer. Not bad for an OEM battery.
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Last edited by llcd; Nov 12, 2017 at 10:44 PM.
I recently bought a 2011 S350, and when I realised on the second day (a Saturday) that it was the original battery, I looked for a replacement -- which I planned to pick up the following Monday. The car used to 'live' at the coast, with temperatures not falling below 16 degrees C (61F). I live 200m above sea level, and that night had 3 deg C (37F). When I tried to start the car on Sunday, it did not start. Battery dead.
The issue with today's batteries is that they die almost instantly. I have no desire to get stuck based on a predictable failure, hence, will pro-actively replace any car battery older than four years; which is way cheaper than the cost of towing and workshop replacement.



