Hundens

Well I joined the club this morning. I have been getting a message "battery partial charge" on MB Connect for some time. This AM the cargo door would not release by its handle and there was a warning on the dash in yellow "12 volt battery" so I got out the Ctek battery manager I keep for when the other machine goes into seasonal storage. The US manual (p.385) has a good diagram, but the written instructions are incomplete. It only mentions the positive connection.

robert c

The negative would go to any good ground bolt nearby
Robert

JTK44

see post #2: next to the red (+) terminal there is an exposed bolt which is the negative terminal

Hundens

Right you are. There are three bolts that hold a frame member and a brass "terminal" for the negative lead It is clear on the diagram in the manual even though there is no written description. Nice of MB to color code things.

konigstiger

parkwood

Thanks to all who answered. We had 8 weeks hard lockdown and now can go out but only in a max 100km radius from home. The car sat at least 4 times for 6 continuous days after only a 10km run. It would show 11.7 on the output menu in the vehicle section of command. I used my charger for usually 5 or 6 hrs and it would get to 11.9 or 12 volts and after a few days it would drop back a couple of points. She always started as normal though really fast as ever and she is diesel. The car did sink slightly too on the air suspension.
I am cautious about leaving her hooked up as a bad storm blew my better charger so that is totally destroyed (the one I use seems to have lost its winter function). Seems they are rather vunerable things.
eco stop start was working but of late seems not too. I had the aux battery in my c class replaced and fear the same will happen again. It does seem to need regular charging.... it is not an actual battery by the way but some sort of electronic system with capacitors the c class thread has good discussion about it.
I have had a few longer runs so have got a bit laissez faire about charging the battery but wonder what might be the effect long term on battery life but not much I can do about it. Still waiting on changing the winter tyres and the seatbelt recall🙄

Jerberos88

Newbie here, just bought a ctek mxs 5.0 to charge a w213 battery.

Can someone tell me if I need to put the ctek charger in vehicle AGM mode - what happens if I didn't?

2012 merc amg

Pretty sure it automatically detects at least it does with my charger even though not a ctek.

Jerberos88

It is the original battery, their charger did not detect. I spoke to CTEK support and they said to put it in AGM mode. Also asked about recon and they said agm batteries unlike lead acid do not suffer from desulfication so it is not needed but can be done once a year. Has anyone tried that?