AGM Battery Faulty -

[ecoman]

Wanted to share my experience and ask your opinions please

Called out RAC to a flat battery and after charging at roadside for a while was told battery wasn't taking/holding any charge. Now this is a 9 month old Mercedes supplied AGM battery that the RAC tested as faulty. Tried my own battery charger at home and same result, not taking any charge.

Returned the car and battery to MB to be told battery all good- here's the £120 bill for the diagnostic.

 

[Gazwould]

https://www.actionfraud.police.uk

 

[John Laidlaw]

Ballcocks

 

[Uncle Benz]

What sort of battery charger did you try on it?

 

[ecoman]

Not sure what to do with that, but thanks for your replies all the same

SO..... received a call at 2.30pm to say battery was at 7.2v and they needed car overnight to fully charge and then do a discharge test. Protested a little and they agreed to charge battery for 2 hours and see if it held charge. Called back at 4.30pm to say battery fully charged and passed MB test. said printout showed 95AH.

question: should the test not show CCA? also 2 hours seems quick to fully charge a 95Ah battery and perform a discharge test.

 

[ecoman]

What sort of battery charger did you try on it?

https://www.amazon.co.uk/d/Car-Batt...ck-Decker-BDSBC30A-Battery-Charger/B00275QPWS

but a 40amp version

 

[ecoman]

What sort of battery charger did you try on it?

Roadside was whatever the tech used

 

[AnthonyUK]

https://www.amazon.co.uk/d/Car-Batt...ck-Decker-BDSBC30A-Battery-Charger/B00275QPWS

but a 40amp version

It doesn't specify whether it has an AGM mode.
Max charge rate for AGMs is around 20% so you could charge yours at nearly 20A.

 

[AMGeed]

The battery needs to be fully charged (12.6V+) then tested under load (CCA)
If the CCA is well below the stated output the battery needs changing.

 

[Uncle Benz]

Low and slow, just like a boeuf bourguignon. AGM batteries don't respond well to a fast charger. I'm speculating here, but that may have been your problem.

 

[ecoman]

thank you for the insights.

My charger is a fully auto charger but I cannot see that it has a specific AGM mode if one is needed - It regulates its voltage between 13.8v and 14.9v depending on the drain.

Given the "low and slow" is it likely to be fully charged after only 2 hours?

 

[Uncle Benz]

thank you for the insights.

My charger is a fully auto charger but I cannot see that it has a specific AGM mode if one is needed - It regulates its voltage between 13.8v and 14.9v depending on the drain.

Given the "low and slow" is it likely to be fully charged after only 2 hours?

If they have a very high tech charger, which tbh is pretty likely, then yes, quite possibly. You'll know in the morning.

That, or they have fitted a new battery and you have paid for it...

 

[ecoman]

That, or they have fitted a new battery and you have paid for it...

Yep, exactly what I feared .......

 

[LostKiwi]

That, or they have fitted a new battery and you have paid for it...

That was my first thought ...

 

[Uncle Benz]

Date code will be stamped on one of the terminals. Might give a clue

 

[ecoman]

https://www.actionfraud.police.uk

That was my first thought ...

Date code will be stamped on one of the terminals. Might give a clue

good shout- how should I approach it..... other than my mates over on mercedesclub think you might have ripped me off?

 

[LostKiwi]

Wait till morning and see if it's fixed...

 

[ecoman]

thanks all

 

[Botus]

wow, didn't occur to me the dealer could be a crook.... you should be able to spot if the battery looks new vs 9 months old, I presume if checked at a main dealer they didn't just stop at testing the battery, what about alternator output?.

when u say issue at the roadside do we mean parked up outside the house or out on a journey?

 

[ecoman]

wow, didn't occur to me the dealer could be a crook.... you should be able to spot if the battery looks new vs 9 months old, I presume if checked at a main dealer they didn't just stop at testing the battery, what about alternator output?.

when u say issue at the roadside do we mean parked up outside the house or out on a journey?

TBH my first thought was that they couldn't be........ then after the explanation over the phone about not being able to do anything unless they had it overnight and then 2 hours later all was well and it passed all the tests (including a drain test). The numbers from the test were for AH and not the CCA which I thought the test equipment output as its measure?

It was parked up over the weekend but away from home and without jump leads! Alternator checked out ok (using a spare battery) and the dealership confirmed alternator was fine.