HELP W221 S600 Aux Battery Malfunction re-occurring

[RANA_1]

Hi,

The Aux Battery has been replaced twice and within a couple of months on each occasion I get the Aux Battery Malfunction message.

Any ideas on what could be causing this. All kinds of tests have been done by the dealer and nothing found ?

Thanks in advance

Rana

 

[television]

You must have a drain taking the battery down, my car will stay good for weeks. Something is leaking or staying awake, lots of dealers are not good at finding these problems.

 

[RANA_1]

I concur Malcolm, The problem is they had the car for 3 weeks and couldn't find a leak and eventually replaced the Aux battery.

 

[television]

well if it goes flat again,then a problem. My 2007 batteries are original

 

[RANA_1]

Ah I wasn't clear it has gone flat, I had the fault this morning !

 

[television]

Ah I wasn't clear it has gone flat, I had the fault this morning !

On these cars up to mid 2008 they have 2 batteries, if the Aux goes flat the car should start on the starter battery. The SL also do this.

 

[RANA_1]

Yes it starts and then displays the failure message.
If this is a repeat of the previous failiures the Aux will only charge when the car is driven a long distance but eventually it will permanently fail. I.e. No matter how far the car is driven or the main battery is charged the Aux Battery Malfunction will alway happen:

After which a new Aux Battery will be fitted and the cycle will start all over again !

 

[television]

You would have to drive 1000 miles to fully charge an AGM battery, if it goes flat again you will have a fault.

 

[RANA_1]

Hi I'm confused... my main battery is a AGM. Is the auxiliary battery also AGM ?
Should the AUX battery be charged if the main is on a battery conditioner ?

 

[television]

Hi I'm confused... my main battery is a AGM. Is the auxiliary battery also AGM ?
Should the AUX battery be charged if the main is on a battery conditioner ?

OK you have the Aux battery or main battery as some call it in the boot. The other battery is the starter battery, and this one is not used for anything else.