Starter Battery Worry

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John N

MB Enthusiast
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Mar 22, 2017
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Location
Peterborough. - (Scot on Permanent Tour!)
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GLB 220D 4Matic P+
My car has been sitting unused in my Garage since 26 Dec, this morning I noticed Mercedes Me has the "Starter battery has Partial Charge" message. I have hooked it up to my CTech Trickle Charger hoping that it's just down to Cold Weather and Lack of Use, not the first signs of a Dying Battery. :eek:
 
How old is / are your battery/ies?

It may well be the use it had before Christmas was not enough to fully charge from what you took out of it and with a couple of weeks it's dropped too low.

I had something similar on my aux and main batteries (a year old and 3 month old respectively) - full charge has resolved so far although tomorrow morning will confirm for sure!
 
When I'm not going to use the car for a few days the first thing I do when I put it away in the garage is charge the battery because with the modern ECU controlled alternators you can be certain the car will not have finished the last journey with a fully charged battery. It will still slowly discharge in storage but at least it's had a head start.
 
How old is / are your battery/ies?

It may well be the use it had before Christmas was not enough to fully charge from what you took out of it and with a couple of weeks it's dropped too low.

I had something similar on my aux and main batteries (a year old and 3 month old respectively) - full charge has resolved so far although tomorrow morning will confirm for sure!

I bought it new on the 13 March 19, now has 17,515 Miles on the Clock, just checked and the message has changed to "Fully Charged":D

I have a 100 Mile commute every working day so I suspect I won't see any more problems:dk:
 
When I'm not going to use the car for a few days the first thing I do when I put it away in the garage is charge the battery because with the modern ECU controlled alternators you can be certain the car will not have finished the last journey with a fully charged battery. It will still slowly discharge in storage but at least it's had a head start.

Yeah, this is what I decided to do in future after my car very nearly didn't start after sitting from 24/12 > 01/01 although I was planning a trip to Sheffield and back in a day which may well have negated the need but nevertheless.

I bought it new on the 13 March 19, now has 17,515 Miles on the Clock, just checked and the message has changed to "Fully Charged":D

I have a 100 Mile commute every working day so I suspect I won't see any more problems:dk:

I'd be confident in your situation that you will have no issues.

My commute is 26 miles daily but I have an upgraded sound system with a subwoofer the size of the Blackwall tunnel which I imagine draws a lot of current at reasonable volumes, and I probably had a lot of consumers on in the run up to 24/12 due to the time of year (and I didn't do the aforementioned planned journey above).
 
I bought it new on the 13 March 19, now has 17,515 Miles on the Clock, just checked and the message has changed to "Fully Charged":D
I have a 100 Mile commute every working day so I suspect I won't see any more problems:dk:

If it's like my C Class & SLC, which are 2016/17 models, then you won't have a second battery.
What mine have is a capacitor instead, that does the same job. "Starter battery has partial charge" would not worry me, I used to get messages that said "Starter battery critical - start engine urgently to recharge" or words to that effect. (After a 2000 mile drive from UK to S.France & back!) In any event, Mercedes renewed the capacitor and the messages never came back.
 
I didn't realise the capacitor-fitting went back to that vintage.

In which case the capacitor is the starter battery as I understand it in which case should be fine unless you keep getting the message.

Mine still has the smaller aux battery as the starter battery as the car is a 2013/63.
 
A modern car has stood in a garage for 11 days and the car has informed the owner of a potential fault with the battery ?

This forum - and others probably - is full of battery faults , mainly on modern cars. My 2006 C55 can sit for weeks , (5 weeks was the record outside Gatwick airport last winter) outside in the winter and starts first time on its original 2006 battery ( I have since replaced the 13 year old battery as a precaution ) on here everyone will cry 'yes , but yours is an old car Pete with little electrical demand' I agree. But why then build modern cars with massive electrical demand and fit batteries in them that simply can not do the job - other than keeping the car light to comply with some bull$hit emissions law - and then printing warnings in the hand book about not leaving your brand new expensive car standing for more than a few weeks without charging the battery.

I wonder how MB owners in In the North of Canada or Scandinavia cope ? The mind boggles.

I still think we need a separate section on here purely for battery issues.
 
I hope that a bigger battery is not the answer. Car manufacturers have already increased battery size or number of batteries to cope with the wasteful design of the cars electronics. Mine is an 85 Ah battery which a 1.6 engine would never have been needed as a starter battery 20 or 30 years ago. It's also not about the current consumed when the car is asleep as the figure is no worse or perhaps even less than older cars. What they need to do is stop the waste by having the car reduce the number of computers consuming a large wake up current every time you open a door whether the car is going to be driven or not. Between deliberately not fully charging the battery and then the go to sleep consumption plus a wake up every time you open the door they have made it completely impossible to have the car finish a journey with a fully charged battery which means it's not best placed to survive a long period of storage and can not be fully charged when you start the next journey. That seems to me to be the reason why batteries have got bigger, to enable the car to start on a partially discharged battery.
 
I understood the problem was that modern cars are right on the limit of 12v which I'd read a few years ago when I had my W211 E55.

I don't know enough about electronics to know why that matters but I do know my current steed is a lot more electrically-complicated than my E55 ever was and there is roughly a decade development gap between these two vehicles.

I understand, for example, that a W221 S Class draws 30 amps on I2 before it's started just from all the electrical systems.

This is probably why at least modern COMAND wants to shut down within 3 minutes if the engine is not started!

And I think as technology has moved on and manufacturers compete with other for who has the car with the most gadgets amongst other things, the problem is probably getting worse save for the onset of 48v electrical systems in EVs which may well save the day if 12v is the issue.
 
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The voltage matters because if you have high power consumption then with 12 volts that means high current levels and big cable sizes to cope with that current. Increasing the system voltage enables cable sizes to be reduced which saves cost and weight. With a 48 volt system you can distribute the same amount of power with only one quarter of the current.

Conversely it's the same reason why we moved on from 6 volt electrical systems which were common before the 60's. I owned a 6 volt vehicle which was a pain unless you kept every electrical connection perfectly clean.
 

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