R230 Dual Battery On-board Electrical System

Front (Starter) Battery • Function:

i) supplies electrical power for starter motor armature only
ii) provides back up power to the system circuit

Rear (Systems) Battery - Function:

i) supplies electrical power for entire vehicle (incl. the starter solenoid)
with the exception of the starter motor armature

Everything you need to know about the R230 Dual Battery System

 

Supremely useful - many thanks - especially re not using boot battery for jump-starting

 

Hi the link is not working?

 

This information is not valid for late cars. If you remove the rear battery the starter battery will take over, valid some time after 06-06.

So if working on brakes, take special care on this one.

 

I think the car can start and run just off the auxilary battery, as I did this without realising until I started the car the next morning and the red battery warning light came on, and noticed the starter/front battery was disconnected!

 

Can anybody recommend a quality trickle charger for the auxiliary battery ? I think my battery is on the way out and when I purchase a new one I would like to give it the best chance. This one is probably only two years old so not happy ! Overnight on a proper charger and its still charging at 5 amps in the morning. Any thoughts folks ?

cheers

Ian

 

C Tek MXS 5.0 Ian, was on Amazon recently at £61 with free delivery on prime
Loads of folks use these
Aldi and Lidl do £15 specials occasionally, I have one which works fine but I know of others havent had good experience

 

Thanks for that John.

 

The Aldi/Lidl ones have a major flaw. If you experience a power cut they revert to OFF until you change the mode back to charging. That's fine if you are on hand to re-set but if it happens, 1 week into you being away for 3 months, you come back to a flat battery.

The C-Tek chargers revert to whatever mode they were in before the power cut.

 

The Aldi one i bought had a big flaw, as soon as i turned it on it went pop and never turned on again.

 

^ There you go, 2 good reasons for the Ctek....prices have dropped too, they used to be over £100..

 

As John Laidlow has said, I personally use the CTEK MXS 5.0 here: http://amzn.eu/dW37t1G It has worked perfectly, and has a function specifically designed for the AGM auxillary battery in the boot of the R230. I had a few problems with the battery being constantly low, I gave the battery a solid charge using the reconditioning feature, and battery has been golden since! Highly recommended.

 

Mercedes own charger is a CTEK one in disguise. So CTEK is the answer.

 

Go to a motorcycle shop and get an Optimate charger.
It checks the batteries state and charges as needed.
It is also for sealed lead acid or gel batteries. The battery in the boot is sealed.
These chargers are around £60.
I have 4 of them, one for each bike.

 

A CTEK is cheaper. A bike sized one cant cope with a large car battery (they bike ones are rated to 50Ah). One big enough for the AGM in the 230 is over £110 whereas the CTEK MXS7.0 is under £100

 

I was not talking about charging the big car battery. The bike charger was for charging the small auxiliary battery.

 

Same though! Still not big enough

 

ctek. never had issues with now,5 of them. 12 weeks away and starts straight of or would if i let it .i crank,stop, until oil lights go out ,then allow start.except where pre lube fitted.

 

Excellent link from the OP, thank you. Can anybody confirm the role of the B14 ambient temperature sensor in the charging system? I've got an SL500 with a starting/charging problem that is defying diagnosis, the one thing that is obvious is the ambient temp displayed on the dash is 49.5. I've ordered a new sensor as a starting point, has anybody encountered this before?

 

Temperature alters the charge rate of the battery and the cell voltage fully charged.