New mb auxillary battery or motorcycle battery?

[CIL 7015]

Having, like many on the forum, suffered battery problems over the cold spell I eventually replaced the main battery in the boot of my w211 only to find that electrical consumers in the car still did not work. A check of the small front battery revealed no electolyte so was duly topped up and charged. Car still preventing use of electrical consumers. The question is can I get away with buying a 12v12ah motorcycle battery for around £35 rather than MB original for considerably more?

 

[CIL 7015]

Just checked voltage with multi meter to find small battery at 13v and main at 12.5v. Suspect BCU or alternator fault for non functioning electrics.

 

[grober]

Time to get some fault codes read I think. The dry front battery would possibly indicate overcharging=faulty regulator control pack.

 

[AndyPCD]

yeah I would also agree about getting the fault codes read.

it might have a have a wiring fault thinking the secondary battery is not fitted and this can cause this problem but should show up on a star test

 

[CIL 7015]

Cheers will venture down to my local independent and get codes read. Update to follow.

 

[CIL 7015]

Just had to crawl home after car drained brand new battery to point that braking defective warning came on. Something is failing to put charge back into the battery.

 

[AndyPCD]

If the car is put on a star machine they can carry out a check on the alternator and check it is working correctly.

Does the car have full mb service history

 

[CIL 7015]

Last 3 services have been with an independent

 

[AndyPCD]

The reason i asked if it was serviced at a main dealer you would have mercedes breakdown and they could come out and have a look at it.

Its a shame you live so far away otherwise i have a star machine and would of offered to have a look at it for you