W211 battery keeps dying (Ctek charger)

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mav01987

Active Member
Joined
Jun 18, 2017
Messages
112
Location
Uxbridge
Car
w211
Hi all

I am have a problem where my battery has died after being left for 4 days. The battery was replaced by the Rac in December/January as my old battery was doing the same thing so when they plugged in there computer they had told me the battery was no good so replaced it.

Unfortunately now when I plug in my ctek mxs 10 it goes into standby mode after 2 minutes because it’s not picking up the battery ( the old battery it would still charge and I could still use the car )

According to ctek this happens if the battery is completely sulphated and needs replacing.

I am just incredibly surprised it has drained and completely sulphated within 4 days, is it possible?

Also my computer (icarsoft MB 2) was telling me that my battery control module was faulty when the old battery started playing up ( before RAC replaced it ) but on the RAC computer the battery control module had no faults, it was purely the battery.

Now I have RAC coming out tomorrow to have a look,

Could there be any other components which is making my computer show the fault of the control module and not the RAC computer showing no faults on the control module ? As I don’t mind replacing the control module but I do not want to replace it just for the battery to die again. I feel I replaced my old battery for no reason now [emoji17]


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I'd be inclined to follow your instinct, and your code reader and point the BCM as being at fault.
I'd also pay a MB indy with Star to run a full test on the car, clear the stored codes and see what is current.
It's not impossible for a newish battery to be faulty, but that would also show up on a Star test.
 
Have the alternator output checked. It wont take long for a faulty regulator to fry any battery.
 
Have the alternator output checked. It wont take long for a faulty regulator to fry any battery.

The RAC checked this before they replaced my old battery and alternator checked out fine


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The old battery may have become faulty due to having been fully discharged several times.

So you are right in thinking that the cause may be more than a faulty battery.

The BCM needs to scanned for fault codes using STAR, not a generic code scanner.

If it's not the BCM, it could be an electric consumer that draws too much current and drains the battery. This can be checked by connecting a suitable Ammeter between the battery terminal and the car.
 
So RAC came out told me alternator and starter motor are fine but couldn’t test anything else as I seem to have fried his tester (according to him), the battery was completely flat hence why the ctek couldn’t pick it up.

I plugged in my mb 2 and it’s throwing up codes everywhere, Can I assume this is because the battery is still not fully charged ?

Also on average how much does it cost to check on star diagnostic?

Also as the battery was completely flat it’s not covered under warranty ( not happy)

P.s RAC are useless as I’ve always been told not to jump start a mb due to sensitive electronics but he thought it was a good idea.


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P.s RAC are useless as I’ve always been told not to jump start a mb due to sensitive electronics but he thought it was a good idea.
Some models have dedicated jump terminals, so if done correctly shouldn't be an issue.
 
I plugged in my mb 2 and it’s throwing up codes everywhere, Can I assume this is because the battery is still not fully charged ?

Yes. Once the battery is fully charged, erase all of the fault codes, then check which (if any) come back.

Also on average how much does it cost to check on star diagnostic?

A specialist will charge £20-£50, a dealer £50-£100. But this is just for reading the codes using STAR (which is more comprehensive than the iCarsoft). For an actual fault diagnosis session most garage will charge an hourly rate.

Also as the battery was completely flat it’s not covered under warranty ( not happy)

To be fair, it's not the battery manufacturer's fault...

P.s RAC are useless as I’ve always been told not to jump start a mb due to sensitive electronics but he thought it was a good idea.

You shouldn't jump-start the car from another vehicle with its engine running. But it is permissible to jump-start the car using an external battery.
 

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