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Just for the record, my car is suffering regular low battery/critical battery warnings although it is only a couple of months old. It is on charge now as today the screen display was telling me critical battery and I have received emails. If the car is displaying messages I can't see this is a mercedes-me fault. At the moment it isn't used a lot but then again other cars I have had have had similar treatment without problems. It isn't garaged so charging is not convenient. It obviously needs a bigger battery so it has more capacity to deal with any power use between driving charges.
 

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This is just a quick post script, I bought my A250 six month old with 800 miles on the clock, picking it up in Norwich and drove it back I to Bristol so the battery sould have been fully charged when I got home. I mainly do short trips with occasional long journeys but like others in early lock down received the Critical battery warning.

In post #30 I said that the on board volt meter normally showed 12v+ during normal driving with this rising to 14v+ when coasting.

When I took my car to the dealers in June they replaced the battery under warrenty, presumably because they found that the SOC was not right, i now find that unless the lights are on the voltage during normal driving is 14v+ and during coasting 14.9v, the only time it drops below this is when the engine is stopped when it drops to 12.7v.

My guess is that as my car had only done 800 miles in 6 months it had been laid up for a long time which lead to the battery going flat and damaging it. Any how for now at least I seem to have a well functioning battery :giggle: and what I take from this is if the voltage drops to 12v+ during normal driving I will probably give it a quick charge with my CTEK just to keep it in prime condition.
Glad to hear things have stabilised .. pretty much the same for me..

I am resigned to the fact that you must periodically use a charger as part of your normal routine. Further, you must leave your car on a charger if you go away.

They, I believe are the new realities of life. Without knowing battery SOC at any point and whether the battery is charging or drawing power when driving, it pays to use the charger, to be sure, to be sure.

And of course charging the battery fully before going away on leave, and leaving it on trickle charge while away.

My car has been checked over by the dealer and tweaked. I have yet to test the stand by readings as I have previously. I will, but at my leisure, as I am really really over the testing thing. It is what it is.

I have been advised the standby has improved noticeably and my gut feeling is the alternator is charging more readily than before. Watching the dial it seems the charging function is much more responsive. So that is positive as well.

I feel the car is now stable, it holds a charge longer than previously, and will be reliable. And like you, I will use the charger to provide additional confidence and to make sure the battery charge levels are maintained long term.
 

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A180 AMG Line Premium Plus Auto with Distronic (the one bit I wanted!)
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Did a good run yesterday (80 miles) just to charge the battery and bought a Ctek and gave it four hours on that. Reading 12.6v at that point (up from 11.7). Never been sure whether I was playing around with buttons which was causing previous battery warnings so I am avoiding that and checkeing daily now. In 24hrs dropped to 12.3v.
 

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Did a good run yesterday (80 miles) just to charge the battery and bought a Ctek and gave it four hours on that. Reading 12.6v at that point (up from 11.7). Never been sure whether I was playing around with buttons which was causing previous battery warnings so I am avoiding that and checkeing daily now. In 24hrs dropped to 12.3v.
As you will have read I did a lot of testing a few months ago and found that the only way to get a reasonable idea of the daily voltage drop is to not use the car for a few days, open the bonnet, lock the car up and test the voltage at the battery with a meter and test at the same time if day.

Of course if you have a State of Charge meter all the better but not many of us have.

Any other way just adds a whole load of variables that make any readings meaningless.

I found that testing this way I had between 0.2 and 0.3v drop per day (possibly due to temp difference), this didn't seem high but it is higher than I would have expected which the dealer agreed with. Apparently they have a diagnostic tool that enables them to historically look at what has been using battery when the car is locked up & on mine they found that one of the CAN bus had been waking up too often so they reset it & put a new battery in. All good for now.
 

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Did a good run yesterday (80 miles) just to charge the battery and bought a Ctek and gave it four hours on that. Reading 12.6v at that point (up from 11.7). Never been sure whether I was playing around with buttons which was causing previous battery warnings so I am avoiding that and checkeing daily now. In 24hrs dropped to 12.3v.
Just a thought, and my 10cents worth of advice, consider dropping the car into the dealer and having the battery checked to see if it will hold a charge.

Not sure of your driving pattern but,

Short trips can drain the battery, but regular long trips to charge the battery can be inconvenient.

If the battery is a dud, best to get it replaced. From what you have mentioned you have received multiple battery critical messages and that is not good. It is possible that your battery will not hold a charge and thus have a bad battery.

A battery test by the dealer will require the car to be left overnight, so it is inconvenient but better in the long run and it can allow the dealer to consider if other tweaks may help.

I am getting the idea that the dealers may be getting more expertise in resolving these issues 😊
 

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Thank you for your helpful comments. I intend to book the car but wanted a clearer picture of whether the battery was dropping of it's own accord. I had used the in-car display, leaving it long enough to settle, but I take your point Mac and will open the bonnet and test at the battery.
 

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Wow, I thought the replacement battery had eased your discharging problems @First and last, clearly not.

I'm sorry I cant offer any words of wisdom on this except to say that my dealer has said that when they hook a car up to their diag machine they can see which module in the car is putting a load on the car when it's switched off and locked, in other words what is switching itself on and off and draining the battery. With this knowledge they 'should' be able to then do something about it.

In your case,for what ever reason, they don't seem to be doing this. All I can suggest is use this snippet of info to challenge them and ask why they have not found the cause of your battery drain and then give them just one last opportunity to repair it, otherwise you will reject the car (if this is what you can do in Australia). I would suggest doing this in writing addressed to the general manager of the supplying dealership.

I cant see what else you can do, your battery problem is far different from the 3 plus week drain that many of us have experienced in lockdown, so your car seems to have a clear fault on it that needs repairing, as you have given MB several opportunities to repair it you need to bring this to a head one way or the other.

Best of luck
Glad to hear things have stabilised .. pretty much the same for me..

I am resigned to the fact that you must periodically use a charger as part of your normal routine. Further, you must leave your car on a charger if you go away.

They, I believe are the new realities of life. Without knowing battery SOC at any point and whether the battery is charging or drawing power when driving, it pays to use the charger, to be sure, to be sure.

And of course charging the battery fully before going away on leave, and leaving it on trickle charge while away.

My car has been checked over by the dealer and tweaked. I have yet to test the stand by readings as I have previously. I will, but at my leisure, as I am really really over the testing thing. It is what it is.

I have been advised the standby has improved noticeably and my gut feeling is the alternator is charging more readily than before. Watching the dial it seems the charging function is much more responsive. So that is positive as well.

I feel the car is now stable, it holds a charge longer than previously, and will be reliable. And like you, I will use the charger to provide additional confidence and to make sure the battery charge levels are maintained long term.
Just a quick update.

I am definitely getting a better charge in the battery whilst driving the car. The alternator is more sensitive and charging more often and longer than before whilst driving.

On one occasion after normal driving around the local area stopping starting shopping and getting things to eat i.e. Out and about for half a day, I returned a GAIN of 10 wks battery charge ( stand by power readout ) ... yowza, the only way I got that sort of gain before was after around 200km drive and the other day after a simple drive of about 2 kms up the road in school pick up traffic (read stop/start) I gained three wks.

This totally excites me. Before I worried that even if my battery was low but the car would start, Iwould flatten the battery after driving let’s say to a doctors surgery only a short distance away. and be stranded. I was consistently losing battery charge whilst driving the car. As well as in lock down.

My “smart” alternator is now way way more smarter.

So in summary to get over my anxiety, I have

  • Had a new battery installed under warranty
  • Bought a charger that seemed to condition the new battery and improved battery performance. Allowing it to hold a charge better.
  • Had the car tweeked at the dealer and now have a smarter alternator, possibly due to new software
And thus now have confidence that under my normal urban driving my battery and car will support my daily needs and I have a charger in reserve to top it up and keep the battery in good condition.

I have not tested battery drain in “ stand by” mode yet ( I have the charger so no urgency anymore, and not sure MB or myself can do any more than has been done to resolve it, if it is still not right) but will test it when we go into lock down again which I expect will happen soon, as the virus spreads it’s second wave.

I may not be any wiser as to the actual cause and what actual improvements were made as no clear explanation has been forthcoming but I can live with the outcome now with less anxiety, and have the charger in reserve ( and for when I go away) to cover any shortcommings.

The real takeaway that gives me pleasure is the smarter alternator, love it, love it, love it.
 

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Sorry, but I have absolutely no idea what you mean.

Is it something to do with UK culture that is going over my head?
It sure is, it went over my head and I'm British 🤣

I had to look it up, she is some sort of minor TV celeb

@veeeight you are giving away your viewing habits 🤣🤣🤣
 

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Just a quick update.

I am definitely getting a better charge in the battery whilst driving the car. The alternator is more sensitive and charging more often and longer than before whilst driving.

On one occasion after normal driving around the local area stopping starting shopping and getting things to eat i.e. Out and about for half a day, I returned a GAIN of 10 wks battery charge ( stand by power readout ) ... yowza, the only way I got that sort of gain before was after around 200km drive and the other day after a simple drive of about 2 kms up the road in school pick up traffic (read stop/start) I gained three wks.

This totally excites me. Before I worried that even if my battery was low but the car would start, Iwould flatten the battery after driving let’s say to a doctors surgery only a short distance away. and be stranded. I was consistently losing battery charge whilst driving the car. As well as in lock down.

My “smart” alternator is now way way more smarter.

So in summary to get over my anxiety, I have

  • Had a new battery installed under warranty
  • Bought a charger that seemed to condition the new battery and improved battery performance. Allowing it to hold a charge better.
  • Had the car tweeked at the dealer and now have a smarter alternator, possibly due to new software
And thus now have confidence that under my normal urban driving my battery and car will support my daily needs and I have a charger in reserve to top it up and keep the battery in good condition.

I have not tested battery drain in “ stand by” mode yet ( I have the charger so no urgency anymore, and not sure MB or myself can do any more than has been done to resolve it, if it is still not right) but will test it when we go into lock down again which I expect will happen soon, as the virus spreads it’s second wave.

I may not be any wiser as to the actual cause and what actual improvements were made as no clear explanation has been forthcoming but I can live with the outcome now with less anxiety, and have the charger in reserve ( and for when I go away) to cover any shortcommings.

The real takeaway that gives me pleasure is the smarter alternator, love it, love it, love it.
I'm so pleased that you have a working car at last 😎
 

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So here I am at a Mercedes dealer waiting for my car to be serviced, when I get a message from Mercedes Me that the charge level of my car's starter battery is critically low. A walk over to the part of the customer area that looks out on to the workshop, and my car is on the lift with its bonnet open and all its lights are on! Could these two events be related??
 

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I wouldn't worry too much about this, well in my case anyway, My starter battery was on critical during the first lockdown for 4 weeks, and when I came to start it for the first time in around 6 weeks, it fired up no problem.
 

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Hi, I’m looking to see if any other have had issues with their 12v batteries. My car is almost 3 years old and is due its first mot and it’s service next month. My battery is showing as partially charged. I drive each day around 38 miles, on mercedes me after my daily journey it states fully charged and then within a few hours it states partially charged. My question is, is this normal? Never had this issue prior to now. Also how long should a battery last. After how many years do mercedes recommend the battery be replaced? Would this be something that could be changed under the warranty as surely a battery should last longer than just under 3 years. Any info would be appreciated. Thanks
 

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Does you start stop work?
that’s one of the symptoms that your battery isn’t up to full state of charge.
If your start stop doesn’t work, tell the workshop that, ask them to check the health of the battery and replace it under warranty if faulty.
 

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Hi, I’m looking to see if any other have had issues with their 12v batteries. My car is almost 3 years old and is due its first mot and it’s service next month. My battery is showing as partially charged. I drive each day around 38 miles, on Mercedes me after my daily journey it states fully charged and then within a few hours it states partially charged. My question is, is this normal? Never had this issue prior to now. Also how long should a battery last. After how many years do Mercedes recommend the battery be replaced? Would this be something that could be changed under the warranty as surely a battery should last longer than just under 3 years. Any info would be appreciated. Thanks
How long a battery lasts is often a factor of how it is used. Car batteries last longest if they are kept fully charged so modern charging systems are no friend of batteries as they are designed to improve mpg by reducing the charging current from the alternator (ie load on the engine) in preference to the longevity of batteries.

I bought my A250 at six months old with just 800 miles on the clock so it is a reasonable bet that it had been laid up for long periods and the battery had probably depleted or even flat for some time. However, there was no obvious evidence that the battery was less than perfect because when driving the dashboard volt meter tended to read 12.3 - 12.5 volts except when decelerating when it went up to 14.5v, then in the first lockdown I regularly got the Critical Battery warning so when it went in for its first service I asked them to look into this and they fitted a new battery. After this the dash voltmeter read 14.7v most of the time except after a long motorway run when it dropped to 12.5v but soon recovered after some town driving which seems to suggest that if a battery is in perfect health we should see a 14.5v+ when driving in town but it also tells us that when driving on Mways that the charging system will only keep the battery partially charged.

But back to your battery, after 3 years it would be handy to have a new battery under warranty so telling the dealer that your battery is not holding its charge overnight might be enough to get them to replace the battery, particularly if you explain that you don't want a hefty bill for replacing the battery just when the warranty runs out.
 
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