Charger says 100% full - Car says critically low

[Devizes2008]

Hi

I have an S213 220d and it is now 3 years old. I don't drive it much and now since the Covid saga even less, so that the Me app keeps warning me that the battery is critically low. So far the engine always started; I try to drive it every Friday afternoon for about an hour which gives me another week of no warning messages. However, I would prefer not having to drive it and charge it fully. To help with that I have bought a trickle charger off Amazon, but have now returned it because it kept saying the battery was charged after about 3 hours charging but the car kept warning me that it was still critically low. I bought a more expensive one CTEK but it does the same thing. What am I doing wrong? When I drive the car for an hour it goes from critically low to partially charged which indicates that the battery is OK, right?
Any idea what is happening?

 

[AMGeed]

Have you put a multimeter on the main battery to see what voltage it is reading with the car resting? It should be around 12.7v fully charged. Screwfix sell an inexpensive one for under £10.
If the app is showing "partially charged" its not yet reached fully charged, which an hours run once a week won't do.

Did your Ctek go through all the battery modes until it reached a full charge?
If it did, then I'd suspect a failing battery. At 3 years old and assuming its not been replaced, it may be time. AGM stop start batteries don't seem to last long.
If you have a small auxillary battery in the boot I'd check that too to rule out low voltage.

Finally, do you trust the Mercedes Me app is giving you the correct info? The multi meter test will help determine that.

 

[OneForTheRoad]

Buy a proper battery charger 4 to 8 amps and use that. Some batteries can get stuck in a transition period and need a good shake up.

 

[John]

I'm thinking it could be complaining about the secondary / auxiliary battery (which is either a proper small battery or a capacitor in your car).

If you are connecting a battery charger to a main battery and the trickle charger is connected, you should be able to read the voltage and see the status on the battery charger.

If that is fine, it's not likely to be the main battery - especially if two different chargers are doing the same thing.

If you can, identify what you have: Where is auxiliary battery in w213 E220d located? | Parts, Maintenance & Servicing

If you have a capacitor, that can only be charged by driving the car for long enough as far as I am aware. Drive the car for say 30 minutes > 60 minutes and see if the warning goes away. If so, don't worry about it.

If you have a proper aux battery, charge that up - I've run some temporary wires from my aux battery from behind the trim and into the boot. I don't have the same car as you and I do mine once a week as after the first recharge, it takes a few seconds - I leave a trickle charger on the main battery all the time.

Regardless of what you have, keep your main battery maintained with the charger you bought and do the aux battery periodically too.

 

[markjay]

Mercedes me app says 'battery critically low'.

Car dash says nothing and battery seems fine.

Now, who do I believe? Hmm... let me think...

 

[Petrol Pete]

Hi OP, Many modern Mercedes Benz cars with stop start (especially ones that don't get driven much) will break down within 3 years due to battery failure of one type or another. Get used to it.

My view is that virtually ANY car should be able to stand doing nothing for a few weeks without breaking down (because not being able to start its own engine is a breakdown in any road car) but I might be in a minority on here as most think its normal to have to buy battery conditioner and plug the car in like it is some sort of a F1 pampered technical masterpiece that needs to be spoon fed.

People will bang on about how modern cars have massive electrical loads , etc, etc It's all bollock$ , it's just making excuses for poor design. If something needs a stronger battery then fit it or make it fit or decrease the load.

They choose not to , so these days the expensive batteries in modern MB's are consumables just like windscreen wipers and brake pads. Yes, car batteries have always been consumable items but my guess is some owners have probably been forced to replace their car battery(ies) before they have even had to replace the windscreen wiper blades/tyres/brake pads/brake fluid etc.

The quest to meet emission standards have pushed manufacturers to build these systems I just wonder if they factored in the environmental damage caused by a car might have to have 6 , 8 or even 10 new batteries during it's life time. They don't really care , as long as it squeezes past it's warranty period before the batteries die...

I know saying anything about this subject on here normally attracts an icy reply , my request for a separate section on batteries on this forum has fell upon deaf ears , even though it seems to be a big subject close to many hearts.

You 3 year old Mercedes Benz has not broken down yet, but it sounds like it soon will . Good luck.

 

[daveenty]

My W213 was always giving me notifications regarding a low battery. A known and common issue apparently.

I ended up just ignoring it as it seemed to be messaging me every other day. I believe that there's a software update for some module or other to prevent it doing it, but good luck getting a dealership to help with that one.

 

[barian]

As stated, this does seem to be a known fault. I would get a "partially charged" warning after less than a week parked. I didn't let it go any further than that. My dealer allegedy did a software update, which seems to have improved the behaviour, although I think the app is still a bit over-sensitive. The advice was that if I wasn't getting a warning in the car itself (on starting) then not to worry, which rather defeats the object of having remote monitoring.

 

[SW18]

I’d be surprised if a CTEK charger is wrong, they’re super-clever. Maybe get someone else to try the CTEK on their car (ideally someone with an old car that’s been standing for a while) to test that the charger’s doing its stuff.

 

[Deleted member 55947]

On the other side of the query I had a very flat battery, you couldn’t lock the car, but the Me App said battery was fully charged. I’d ignore the App

 

[chrisk2010]

Something that hasn't been mentioned is the battery amperage, even though lead acid batteries can show full voltage but eventually towards the end of it's life it won't be able to hold the amperage anymore.

This is more commonly encountered with forklifts traction batteries where they have either been opportune charged, left for a long time without a charge or just simply old. Without going into the science of it and boring everyone to death they can sometimes be brought back with a charger that conditions the battery or re-aciding but mostly it's easier to just replace them as car batteries for the most part are sealed.

Assuming that of course it is the battery and not any of the issues others have mentioned but it's a good place to start.

 

[Dazsw]

The battery charger may have charged it to 100% of its current state, not 100% of what it was when new, seen this before, battery was gubbed.

With the amount of electronic equipment on modern cars there are lots of things that could be wrong, or nothing at all

 

[John N]

^^^^^
Gubbed!

 

[barian]

Thinking about the original post a bit more, I wonder whether, if the car is not woken after being charged, the battery status in the app is not updated. Probably not the explanation, but I wonder if it worth checking.

 

[mark999]

If you can get hold of a memory saver it may be worth trying the recon mode on the CTEC, with the battery disconnected.
Mark

 

[rf065]

Don't bother wasting time with any of these fixes, the Mercedes Me app is the problem.
I got the message "starter battery critical - start engine" every day on a trip from UK to France/Spain/France and UK again covering a few thousand miles in a couple of weeks.
There was nothing wrong with the battery and it was never flat or even partially charged.

 

[Bobby Dazzler]

Apparently AGM batteries (used on cars with stop-start) don’t like recon mode