Recommissioning my W211…

[Bobby Dazzler]

The batteries in the boot and I seem to remember it being AGM , my only doubt is that there’s 2 batteries (there’s also that smaller Aux one for the brakes somewhere in the engine bay) so will this be charging both do you think? (As it’s currently connected directly to fuse box)

If I remember right the circuit doesn’t charge both, the charging points in the engine compartment will charge the starting battery, but probably won’t charge the other smaller battery. I’ve never charged the other small battery so I would wait for guidance from someone more knowledgable than me before doing it.

 

[Wearsthefoxhat]

Both of the batteries charge up on mine, charger connected to the AGM battery in the rear… 2005 S211.
The other smaller battery is under the pollen filter, pass side engine bay.

 

[Skd884]

Disconnect the battery if storing car.

 

[bolidemichael]

Both of the batteries charge up on mine, charger connected to the AGM battery in the rear… 2005 S211.
The other smaller battery is under the pollen filter, pass side engine bay.

How can you tell that both are being charged when connected from the rear?

 

[Lenny63]

I rate the Ctek MXS 5.0. Had mine about 6 years and the recon function works well

 

[Smiley]

Disconnect the battery if storing car.

In my experience it is better to connect a CTEK or similar intelligent trickle charger - I used to disconnect batteries but had a couple of problems in the past when the batteries were reconnected - audio systems not working, convertible roof needing reprogamming etc. Nothing terrible but a nuisance nevertheless. I've also found that the CTEKs have paid for themselves in longer battery life in little used cars

 

[Wearsthefoxhat]

How can you tell that both are being charged when connected from the rear?

I had tested both batteries and planned to charge the rear one first. Once the trickle charger had charged the rear battery I, out of interest checked the front battery, that too was now at >12v and iirc 7ah.. I did connect the charger and it showed full after five mins or so.
Since then I have only ever connected the rear battery and had no problems with the front one. In fact I have just replaced the front one, it was from the MB parts counter and six years old, still above 12v and still 7ah..

 

[bolidemichael]

I had tested both batteries and planned to charge the rear one first. Once the trickle charger had charged the rear battery I, out of interest checked the front battery, that too was now at >12v and iirc 7ah.. I did connect the charger and it showed full after five mins or so.
Since then I have only ever connected the rear battery and had no problems with the front one. In fact I have just replaced the front one, it was from the MB parts counter and six years old, still above 12v and still 7ah..

Thanks a lot -- some peace of mind.