All batteries are not created equal

[Horrgakx]

A friend with a W211 had a lot of electrical issues, the main problem being that the battery would be flat very quickly. He had a non-Mercedes battery fitted before this started, a higher amp-hour capacity than the original version.

Mercedes tore their hair out for ages trying to diagnose what was wrong until a certain mechanic said "that's not an approved battery", changed it for an MB one, and everything has been fine for over a week.

So, what's the difference, that would explain this issue, between an approved MB battery and a run-of-the-mill higher capacity one?

 

[Satch]

When I had my battery changed asked if I could upgrade to a higher capacity one was told that was a very bad idea and that only "specified" batteries should be used.

Sounded like BS to me but having been asked to checked the answer came back that the battery management software works off a number of basic assumptions can be tripped up by a non specified battery.

 

[AdamG]

I think modern mercedes need "Absorbent glass mat (AGM)" batteries. These have different charging/discharge characteristics.

Unfortunately these batteries are a lot more expensive.

Adam

 

[rlowy]

Not sure if this is any help but I had a new battery fitted in my W211 E55 late 2009 at the dealer as it was not going flat but after a few days would struggle to start the car and I had a red battery warning sign showing.

Start the car run it for a very short while start again, no problem no warning sign.

Everything seemed fine after battery fit untill I left the car for 10 days then the same problem. In truth it was not causing a problem so when I had it serviced in May this year I mentioned the problem again.

The diagnosis was that the new main boot battery was fine but the second battery under the bonnet (I was unaware of this one) needed replacing. I had that done and everything is perfect.

Regards

Richard

 

[ecossebev]

If you were to find out who makes/supplies the batteries for Mercedes, buy the branded make from a motor factors a bit cheaper possibly?

 

[rlowy]

My battery in the boot is Bosch