T6.1 Battery keeps switching between charging and discharging

[rollingbyte]

Hi California community

I have a weird issue with my T6.1 ocean. Sometimes (not always), while driving the leisure batteries keep switching between charging and discharging mode.
I have seen values ranging from -20A to +80A.
It can go on like that for 30 minutes+ while driving. After sometimes, it starts charging as expected.
I cannot really explain the -20A, as I have only the fridge connected.
I tried enabling the "max charge", it doesn't help.

Did anybody already experienced this issue or has an idea what it could be?

I captured on a video:

Thanks for your advice and help

 

[jakubklapka]

This is normal and i think it's called "smart charging", basically the car disconnects the charger when the engine is under load to save fuel.

 

[Blue Yonder]

Hi California community

I have a weird issue with my T6.1 ocean. Sometimes (not always), while driving the leisure batteries keep switching between charging and discharging mode.
I have seen values ranging from -20A to +80A.
It can go on like that for 30 minutes+ while driving. After sometimes, it starts charging as expected.
I cannot really explain the -20A, as I have only the fridge connected.
I tried enabling the "max charge", it doesn't help.

Did anybody already experienced this issue or has an idea what it could be?

I captured on a video:

Thanks for your advice and help

It could be due to how the not so smart charge relay logic works. When you start your engine the relay opens disconnecting the leisure batteries from the engine battery. Once the engine is running the relay closes and all batteries are no connected. Given you just started your engine then it will likely be at a lower potential/ state of charge compared to your leisure batteries thus a charge voltage will flow from the leisure batteries to the engine battery until there potential is balanced. During this time you will see a minus on the battery display. Small point if you have a T6 and you want to emulate the T6.1 max charge feature then just turn on a heated seat. This cause the alternator to put out maximum charge all the time while the engine is running

 

[rollingbyte]

It could be due to how the not so smart charge relay logic works. When you start your engine the relay opens disconnecting the leisure batteries from the engine battery. Once the engine is running the relay closes and all batteries are no connected. Given you just started your engine then it will likely be at a lower potential/ state of charge compared to your leisure batteries thus a charge voltage will flow from the leisure batteries to the engine battery until there potential is balanced. During this time you will see a minus on the battery display. Small point if you have a T6 and you want to emulate the T6.1 max charge feature then just turn on a heated seat. This cause the alternator to put out maximum charge all the time while the engine is running

Thanks for the additional details @Blue Yonder
I have been researching the "smart" alternator and indeed, something must be happening there... I have been traveling the Dolomites recently and observed even weirder behaviors.
Before that trip I went to the local VW dealership. They didn't really know what was happening and changed a Relay (assuming it is the relay you mention). It did not help.

My impression so far is that the alternator is just not running at all. I think it is controlled by the camping control unit?

What I observed (and experimented):
- The cycle of charge / discharge can go on for > 30 minutes of driving
- Yesterday I drove for 1 hour, and when I arrived at the next camp site, the battery was more discharged than before I left... While driving I saw between -20A to -30A on the display
- I saw the current draw increase when I turned on the seat heating, which seems to indicate that all the current draw from the vehicle was taken by my leisure batteries
- I have a T6.1 ocean, I enabled the Max Charge button / disabled it, but nothing changed.

Something to note:
Last year, the VW dealership changed ONE faulty leisure battery (under the driver seat).
I am wondering if that is confusing the CCU and causing all the troubles?

My assumption would be that when I turn Max Charge, the "smart" alternator should be running all the time?

Thank you for your help and insights. Much appreciated.

 

[chockswahay]

I have found that if the engine battery is below 80% and the leisure battery above 80% the smart charger will dump the excess until both are equal. To overcome this (and if needed) I turn on the Max Charge which overides this dumping and just fills both battery systems until full. The smart charger in my opinion is actually not so smart!