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Leisure battery not charging while driving

funkyegg

Member
Sorry for starting a new thread on this but I really need some help please. My leisure battery doesn’t charge while driving (even for long journey) and I have been back and forth with my local dealership, Mercedes Epsom for a few times now and the issue is still not resolved. The vehicle is currently with them and has been there since last Wednesday as they couldn’t figure out what’s causing the issue so they logged the case with the Technical Department in Milton Keynes. However, all they advised was that the battery would need to be charged through the charging cable to be at least 12.5v before the alternator charge can kick in. When I took the vehicle in last week, the battery was 50% charged with 12.4v, but I’m not sure if charging the battery to above 12.5v would make any difference as I previously tested the vehicle when there was only two bars dropped and with higher than 12.5v (although not 100% certain). Please can anyone confirm this or possibly even offer a solution?
 
WILLH

WILLH

Active Member
VIP Member
Do you disable(turn off)engine start/stop off when driving?I believe the leisure battery does not charge if you do this
 

funkyegg

Member
Do you disable(turn off)engine start/stop off when driving?I believe the leisure battery does not charge if you do this
Well, I do disable engine start/stop indeed! I would be really embarrassed if that's all there is... Is this mentioned in the manual at all as I don't seem to be able to find it.... Thanks
 
WILLH

WILLH

Active Member
VIP Member
I had the same problem early on in my ownership and likewise I disable the start stop all the time.I read about it either here or on the Facebook page and it does seem to be the case as I tolerate the start stop now and my battery charges!
 

funkyegg

Member
I had the same problem early on in my ownership and likewise I disable the start stop all the time.I read about it either here or on the Facebook page and it does seem to be the case as I tolerate the start stop now and my battery charges!
Great info, I will tell the dealership tomorrow (I'm a bit embarrassed though if that's the case). Cheers
 

Spekky

Member
I have been plagued with leisure battery problems as well and used the same dealership. My problem was that the battery would not charge fully, or hold a charge and eventually died and dropped to 6V and would not respond to the cable at all. After driving 60 miles, the battery started working and showed charging bars on the console when plugged in once again, but still dropped power quickly and it has been replaced within the past few days. I wait to see how this works. As far as the start stop function. This would only start to work after a drive of about 100 miles and the dealer blamed the poor battery function.

I don't believe from my experience that the cable charger is needed to bring the battery up to a voltage where the engine will then charge it. In fact completely the opposite. I wonder if you (and I) suffer from issues with the charging function which Mercedes has yet to resolve.

I have had the vehicle for 16 months from new and the battery function has been a constant problem. Other threads have suggested that the battery can be damaged before delivery by being left with a very low charge by the manafacturer/dealers.
 

funkyegg

Member
I have been plagued with leisure battery problems as well and used the same dealership. My problem was that the battery would not charge fully, or hold a charge and eventually died and dropped to 6V and would not respond to the cable at all. After driving 60 miles, the battery started working and showed charging bars on the console when plugged in once again, but still dropped power quickly and it has been replaced within the past few days. I wait to see how this works. As far as the start stop function. This would only start to work after a drive of about 100 miles and the dealer blamed the poor battery function.

I don't believe from my experience that the cable charger is needed to bring the battery up to a voltage where the engine will then charge it. In fact completely the opposite. I wonder if you (and I) suffer from issues with the charging function which Mercedes has yet to resolve.

I have had the vehicle for 16 months from new and the battery function has been a constant problem. Other threads have suggested that the battery can be damaged before delivery by being left with a very low charge by the manafacturer/dealers.
Thanks for the reply Spekky. My leisure battery had been replaced at the beginning of the year by the same dealership as I left it uncharged for too long so the battery wouldn't hold a full charge no matter how long it had been plugged in. Since the battery replacement, it charges perfectly when plugged in but I couldn't charge while driving the vehicle. I always disable stop/start before any journeys so I wonder if this is what prevents the leisure battery from being charged. I am going to collect the vehicle from the dealership today and take it for a drive with stop/start enabled to see if it resolves the issue. If you have not replaced the battery, I think you should get them to replace it under warranty. They didn't ask any questions when they replaced mine.

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askho

Member
Do you disable(turn off)engine start/stop off when driving?I believe the leisure battery does not charge if you do this
REALLY!!!??? Why would that be?
I always drive with the stop/start function disabled. I hate that feature.
 
WILLH

WILLH

Active Member
VIP Member
Because most MB dealers had(still have) little understanding of the MP model many vans were left for months with an uncharged leisure battery which damages it and the buyers of these vehicles then had an unsatisfactory battery and all the associated problems that causes right from when they picked up the vehicle.

From what I understand the alternator has an ‘intelligent’ system where it can charge and maintain both the leisure battery and the normal vehicle battery.I don’t know why disabling start stop would stop charging the leisure battery I can only assume that it is linked to the system that monitors the vehicle battery to make sure that it has sufficient charge to start again during the stop/start process.

I’m sure this has been discussed here before a while back.
 

funkyegg

Member
Took the vehicle for a long drive today with stop/start enabled all the way but the battery still didn't charge for one bit...need to take it back to the dealership again....errrrrrrr

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Andy B

Andy B

Member
VIP Member
I thought I would check with MB direct regarding this. They advised me that disabling the start /stop function would not affect the way the leisure battery charges. However, as I recall, the priority in charging the batteries is:

1. Main battery

Then

2. Leisure (but only after the main battery has reached its normal charge state - this is why a long journey is required to get any charge into the leisure battery)

For reference - I find it better to hook up to the mains when our Marco Polo is at home and charge the leisure battery this way. In fact in the supplementary manual it suggests that if the MP is left standing for a period of time, then the leisure battery should be charged in this manner at least once a month.

Hope this helps.

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Steve B

Active Member
I've noticed that the stop start function doesn't kick in on short journeys and the symbol in the instrument cluster stays yellow, it only turns white after quite a few miles. My Audi is active right from the start in mild temperatures
 

askho

Member
I have a feeling that the stop/start is "intelligent", ie it learns. As I said I hate that feature so I always switch it off when I drive. Very occasionally I forgot to switch it off and yet the stop/start didn't function. Maybe it's because the journey wasn't long enough.
 

BabaJen

Active Member
It's hardly cutting edge technology. I'm a Cali owner but the technology for charging batteries through a split charger is the same and has been for about the last century or so:

The battery should charge from whatever generation source regardless of voltage rating but only when the battery charger detects less than fully charged to prevent overheating.

Stop/start should not affect it in any way at all.

The engine generation source, if the same as the Cali, will only charge the battery to around 90% full. This is because to achieve 100% the last few bits need to be trickle charged, something that can only happen with mains supply.

To preserve battery life the battery should be charged to 100% regularly, at least monthly, achieved by leaving the vehicle on mains charge for 24 hours once a month.

Any failure to charge outside these parameters is a service issue that if the vehicle is within the warranty period should be performed under warranty. The dealer needs a good kick up the posterior if he is not trying to resolve this situation urgently.

My last Cali had an intermittent problem: It would charge quite normally but in warm weather trip out on mains charging if the fridge was being used, and not restart without being unhooked and hooked up again. Engine charging was fine. It was eventually traced to a tiny failure in the wiring loom that caused a break in circuit when it got very warm. It took VW ages to sort but not through lack of effort and with involvement of the customer Care director who found a replacement vehicle from somewhere. I'm saying this not to wave a flag for VW, some of their dealers are dire, but just to illustrate the sort of focus MB should be having in sorting out this problem for you.

You should not need to think about charging or switching things on and off. The vehicle is designed to deal with those things for you. If you have to think, and worry, then the vehicle is not doing what it is designed to do and the responsibility to sort it lays firmly with the dealer.
 
Last edited:

funkyegg

Member
It's hardly cutting edge technology. I'm a Cali owner but the technology for charging batteries through a split charger is the same and has been for about the last century or so:

The battery should charge from whatever generation source regardless of voltage rating but only when the battery charger detects less than fully charged to prevent overheating.

Stop/start should not affect it in any way at all.

The engine generation source, if the same as the Cali, will only charge the battery to around 90% full. This is because to achieve 100% the last few bits need to be trickle charged, something that can only happen with mains supply.

To preserve battery life the battery should be charged to 100% regularly, at least monthly, achieved by leaving the vehicle on mains charge for 24 hours once a month.

Any failure to charge outside these parameters is a service issue that if the vehicle is within the warranty period should be performed under warranty. The dealer needs a good kick up the posterior if he is not trying to resolve this situation urgently.

My last Cali had an intermittent problem: It would charge quite normally but in warm weather trip out on mains charging if the fridge was being used, and not restart without being unhooked and hooked up again. Engine charging was fine. It was eventually traced to a tiny failure in the wiring loom that caused a break in circuit when it got very warm. It took VW ages to sort but not through lack of effort and with involvement of the customer Care director who found a replacement vehicle from somewhere. I'm saying this not to wave a flag for VW, some of their dealers are dire, but just to illustrate the sort of focus MB should be having in sorting out this problem for you.

You should not need to think about charging or switching things on and off. The vehicle is designed to deal with those things for you. If you have to think, and worry, then the vehicle is not doing what it is designed to do and the responsibility to sort it lays firmly with the dealer.
Good info as always BabaJen! Collected my van yesterday after the dealer replaced the relay between the leisure battery and alternator. I will take it for a long drive today to test out if the issue has been fixed.

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