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I have an A200 sport 68 plate, about a week ago I started to get a message on the dash saying 12 volt battery see user manual, spoken to Mercedes me who advised me to leave the car running for about half an hour, next day happened again and then also had a message saying to stop the vehicle and leave running, did that also, the stop start function was also not working at this point, went to the car on Monday and it would not start, roadside attended and got the car going, I went to the dealership and was told this has happened because apparently I don't drive the car enough, granted I have only done 5000 miles in the car but it is still used every day, roadside said the battery was charging fine and had enough charge in it and he was not sure why the 12v battery sign was appearing on the dash. I'm going to pick the car up later on today but have been told they have charged up the battery for me, I personally don't think that is the issue but will see what happens, has anyone else had anything like this happen?
 

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do you have Auxiliary battery in your car? make sure to check on that.

on MBUX, there is section, you can actually look at your battery voltage, when drive you should have 14.7-9 ( new battery ) when park, you should never lower than 11.7-8v,
 

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its at the dealership still, they called me to collect it on Monday saying it was fixed, however when I arrived the car wouldn't start, they called me today with an update saying they had charged the battery fully and went to start the car this morning and a warning notice came up saying to stop the vehicle and leave running, they have had it on the diagnostic machine and no fault codes are registering so they are stumped as to what it could be.
 

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its at the dealership still, they called me to collect it on Monday saying it was fixed, however when I arrived the car wouldn't start, they called me today with an update saying they had charged the battery fully and went to start the car this morning and a warning notice came up saying to stop the vehicle and leave running, they have had it on the diagnostic machine and no fault codes are registering so they are stumped as to what it could be.
suggest them to give you a new battery to try,
 

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So this morning I get a call from the dealership saying the car was ready to pick up, I asked what had they done, she said charges the battery, I asked anything else and she said no, I explained to her what issues the car was having and she told me that the technician was left a post it note to tell him to charge the battery and send it out, I can not believe how terrible the service is so far, anyway I have told them I will be keeping the loan car they have let me use until they have fixed this issue for as long as it takes and they also need to test everything before I take it back. Worse this is that 3 hours after they called to say I could have it back I get an email from Mercedes me saying the battery level is critical so clearly it’s not fixed. Will see what happens next week. Not happy!!!
 

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So this morning I get a call from the dealership saying the car was ready to pick up, I asked what had they done, she said charges the battery, I asked anything else and she said no, I explained to her what issues the car was having and she told me that the technician was left a post it note to tell him to charge the battery and send it out, I can not believe how terrible the service is so far, anyway I have told them I will be keeping the loan car they have let me use until they have fixed this issue for as long as it takes and they also need to test everything before I take it back. Worse this is that 3 hours after they called to say I could have it back I get an email from Mercedes me saying the battery level is critical so clearly it’s not fixed. Will see what happens next week. Not happy!!!

on my A250, if i park for 4-5 days, if i check on Mercedes me, it will says battery level only partly charged, need to charge the battery. the system takes a lot of power, so i bought a battery charger which i will connect to the car 24h/7 if i'm not drive it. to keep battery for longer life.
 

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Discussion Starter #7
Surely that must be a fault, you shouldn’t have to charge a battery on a car that’s a year old or less,
 

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Update, so the dealership called again today to say the car was ready, I asked what had they done to it and they said they had replaced the battery, been to pick it up and have driven 9 miles in traffic, everything seems fine now, stop start works ok so hopefully it was just something simple. Will see what happens in the next few days.
 

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Update, so the dealership called again today to say the car was ready, I asked what had they done to it and they said they had replaced the battery, been to pick it up and have driven 9 miles in traffic, everything seems fine now, stop start works ok so hopefully it was just something simple. Will see what happens in the next few days.
oh, yes! for that Stop and Go, turn it off. your battery will thank you
 

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Another thread bump!

Think I have a battery issue too!

It started with the stop/start not working at all, then after a few days when starting up, after several minutes down the road, randomly I'll get the same message...

6955


So I did, but it's been happening each day and I can't just stop for long when I have work to get to, or on a dual carriageway!

Based on the center screen's information, it says about the charge level...

6956


Not sure if this battery is separate to the charge level, but it shows the voltage at 14.3v and only really rises to 14.5v and back down.

6957


So based on Barthez16 having a new battery, presumably that's the case for me!?

(It's booked in for another issue next week, so I'll of course mention the charge level too).
 

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That’s exactly the same thing that mine was doing too, they changed the battery on mine and it’s been ok ever since, I’m sure it should be covered under warranty,
 

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It better be under warranty, considering the amount I'm paying/have paid already!
Hopefully they have a new battery on site!

You wouldn't think a nearly 2 year old car would need a new battery so soon!
 

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I was on servis "B" last friday, my car is from 2019. The service shoud take max 2 hours, but I spend there 4 hours unfortunaltelly. The reason was that they said they have to change my battery, because the battery was to small and service MB decided to replace it with a more powerful battery. They did it for free as my car has still guarrante.
 

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Yes I get frequent messages that my battery is critical I've charged it up a couple of times. Granted I don't do a lot of miles, My A35 has only 3200 on the clock but it's used every day. Can't remember ever having a car that needed to be driven so often to feed it's gadgets. The stop/start stopped working a couple of months ago, clearly the OEM battery is not up to it. What upgrade battery are you all fitting?
 

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Yes I get frequent messages that my battery is critical I've charged it up a couple of times. Granted I don't do a lot of miles, My A35 has only 3200 on the clock but it's used every day. Can't remember ever having a car that needed to be driven so often to feed it's gadgets. The stop/start stopped working a couple of months ago, clearly the OEM battery is not up to it. What upgrade battery are you all fitting?
There was a thread back in April about this because lots of cars were parked on the drive during the first lock down and receiving the critical battery warning. I was interested in this so I did a great deal of testing which did little other than show that there was some sort of load on the battery when the car was parked up. My dealer looked into it when I took it in after lock down, apparently their diagnostic systems can look at a history file and it showed that one of the CAN bus was waking up more often than it should. They reset this and gave me a new battery and 🤞 it has been fine ever since, like you I do little mileage made up of infrequent short trips. Whether the problem I had was the battery, my car only did 800 miles in the first 6 months so might have been standing for some time with a flat battery, or the CAN bus issue I will never know.
 

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There was a thread back in April about this because lots of cars were parked on the drive during the first lock down and receiving the critical battery warning. I was interested in this so I did a great deal of testing which did little other than show that there was some sort of load on the battery when the car was parked up. My dealer looked into it when I took it in after lock down, apparently their diagnostic systems can look at a history file and it showed that one of the CAN bus was waking up more often than it should. They reset this and gave me a new battery and 🤞 it has been fine ever since, like you I do little mileage made up of infrequent short trips. Whether the problem I had was the battery, my car only did 800 miles in the first 6 months so might have been standing for some time with a flat battery, or the CAN bus issue I will never know.
That's interesting, do you happen to know if they just changed like for like battery or was it a higher rating? As I mentioned my S/S has stopped working, I suppose to conserve the battery. It does seem ironic that a car with ECO tech tells me to go and drive for 1/2 hr. to charge the battery. It's due it's first service in Feb. so I'll raise the issue then.
 

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They didn't say what battery they put in but I would imagine it would just have been a standard one.

Although I think the problem is exacerbated by only driving short distances the main cause of batteries not being kept fully charged is probably down to the 'smart' charging system being a bit to cleaver for its own good. In the Old Days the alternator just chucked out about 15v with as much current as it could muster but the focus on mpg has lead to smart charging which puts as little load on the alternator as possible which might be leading to batteries not being kept fully charged.

As I said before I did quite a bit of home testing but it was all very inconclusive, largely I think due to the smart charging being so complex as well as me not knowing what it is actually trying to achieve. I know that under acceleration it is supposed to reduce the load on the alternator and on over run it gives maximum output but in between is a mystery. When my original battery was in the car the volt meter in the car showed 12.5 - 12.8v most of the time and 14.5 - 14.8 when coasting. With the new battery fitted I see 14.8v most of the time whilst driving in town but after a long motorway run its about 12.8v which recovers back to 14.8v quite quickly in town.

Coming from a lifetime of conventional battery charging this is counter intuitive as you would expect the opposite, I could put forward various theories but I would be hard pressed to substantiate any of them as there would always be an alternative explanation. What I think I can say from experience is that when I had a fully charged battery (both the original and new one) I normally see 14.8v most of the time when driving in town so this might indicate what is normal for a fully charged battery but then again perhaps not.

Its also worth remembering that the alternator is not designed to recharge a battery but to just keep it topped up so in your case a monthly charge with a CTEK charger might be worth considering.
 

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In common with all other Euro6 spec engines, the engine ECU doesn't allow the "smart" (actually dumb) alternator to charge the battery to more than 80% capacity on the move, the remaining 20% is spare capacity for when you brake, the alternator over-voltages and uses "energy recovery" to top up the remaining 20%.

We've seen this since 2016, in particular some W176 A45 owners having replacement batteries around the 2 year mark - plenty of old threads in that section with exactly the same complaints!

With the W177 and the power hungry MBUX and associated systems, this has just exacerbated the issue.

This has also caused owners of caravans and motorhomes huge headaches, the traditional "split charge relay" system no longer works effectively to charge a leisure battery.

And it's not the length of the journey that matters, it's how much of that journey you spend braking, or coasting to the extent of triggering the over voltage charge required to top up that last 20%.
 

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In common with all other Euro6 spec engines, the engine ECU doesn't allow the "smart" (actually dumb) alternator to charge the battery to more than 80% capacity on the move, the remaining 20% is spare capacity for when you brake, the alternator over-voltages and uses "energy recovery" to top up the remaining 20%.

We've seen this since 2016, in particular some W176 A45 owners having replacement batteries around the 2 year mark - plenty of old threads in that section with exactly the same complaints!

With the W177 and the power hungry MBUX and associated systems, this has just exacerbated the issue.

This has also caused owners of caravans and motorhomes huge headaches, the traditional "split charge relay" system no longer works effectively to charge a leisure battery.

And it's not the length of the journey that matters, it's how much of that journey you spend braking, or coasting to the extent of triggering the over voltage charge required to top up that last 20%.
Well that explains why our batteries are failing so quickly then because batteries degrade rapidly if they are not kept fully charged. Yet another home goal for the environmentalist, we pollute less by employing smart charging but pollute more by manufacturing twice as many batteries 🤣

So many of these 'bright' ideas are just not thought through in my view, if what you say is true someone who does a lot of M-way driving may never have a fully charged battery because you will need a significant amount of coasting to top up 20% of a batteries capacity. It also means that if you have to travel a significant distance to the airport for your holidays you may park up the car with just an 80% and three weeks later get the critical battery email whilst sipping your martini by the pool. Lucky I bought a solar charger 😇
 
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