Leisure battery charging problem – voltage not stable

[szczota81]

Cali 5.1 2015 2.0TDI 4 motion with 2 leisure AGM battery get charging issue after generator failure.

It all started when the isolation relay under the driver's seat started switching between generator and battery by itself (while driving). Few days later, I got an error indicating charging of the engine starter battery. VW service replaced voltage regulator, bearings and overhauled the whole generator. After this repair, it is very rare for the leisure batteries charging voltage (on the camper unit display) to get above 14V. Usually it is 13,7V. Which is probably way too low.

Recently I've noticed that during the drive, despite the generator symbol on the display, the voltage on leisure batteries drops to 12.5V and the current consumption is -3A (negative value). So there is no charging from generator. After some time charging returns, and there is about 6A and 13.9V sometimes 14.2V. And so on and so forth. All the time the generator mark is visible, and all this happen while driving. See picture below.


I add that the voltage on the engine's starting battery is stable at 14.45V (monitored by CTEK Sense). It seems that the generator is working properly.

Fuses checked. If they were even burnt there would be no effect of charging appearing and disappearing.

Do any of you have any idea what could be causing this? Could the relay under the seat be damaged and causing these issues?

Can someone of you record your display while driving so I have a reference of what voltage I should expect! I would be grateful for such a video or photos while parked with engine on and while driving

I will be glad for any ideas.

 

[icic]

Hi did you find the issue behind this and a solution ?

 

[WelshGas]

Hi did you find the issue behind this and a solution ?

Just a point. If you don’t use the Reply button, bottom left, when commentating on a post the the Original Poster never gets a notification and may never see your post unless they check back on the thread regularly.

@szczota81

 

[szczota81]

Unfortunately not. But one week ago the situation began worst even. Now I have no leisure charging at all. Engine battery voltage looks good, 80A fuse is OK. But no charging.
Anyone have idea what can be wrong. I would like to replace relay 2D0 951 253B.
I expect that relay was damaged when during generator failure. Directly before generator failure, there was a lot of strange sound coming from relay which was switching all the time.
I will keep you inform.
@icic Do you have the same problem?

 

[szczota81]

@Loz Your help will be highly appreciated.

 

[szczota81]

Quick update. I removed the seat and checked the split relay. First engine start. There is voltage on both relay cables. On one 14V from alternator on the other 12.3V (battery voltage). I turned the engine off and measured the conductivity between the cables on the relay. Generally as far as I know relay is either conducting or not depending on the signal. Unfortunately mine showed that there is a conduction but with high resistance. I disconnected all three batteries and then with only the engine battery connected I started the engine. The split relay jumped and there was voltage on the second cable. At the same time I checked the conduction between the cables with the engine on and off. Now the multimeter showed a good value 0 or 1. So there is or there isn't conduction. I hooked up all the batteries and charging came back.

Question.
Could this switch be blocked?
Could what's happening be indicative of a fault split relay?
Or maybe the Onboard Supply Controller is giving the wrong control signal.

I would be grateful for any information.

Does anyone know where the fuse S339 75A is located? The one from the second battery.

 

[yossarian]

Does anyone know where the fuse S339 75A is located? The one from the second battery.

This is the cube fuse on the positive pole of the rear battery.

 

[szczota81]

This is the cube fuse on the positive pole of the rear battery.

Hahah I was wondering what is this cube for. Thx

 

[szczota81]

Question
Split relay is controlled by Onboard Supply Controller.
Is it by any chance that the system logic is designed to cut off charging of the leisure batteries in case the engine battery voltage is too low?
I have never had a situation where the split relay malfunctioned when all batteries were well charged.
Does anyone have any information on this?

 

[WelshGas]

Question
Split relay is controlled by Onboard Supply Controller.
Is it by any chance that the system logic is designed to cut off charging of the leisure batteries in case the engine battery voltage is too low?
I have never had a situation where the split relay malfunctioned when all batteries were well charged.
Does anyone have any information on this?

All I know is that the system prioritises the engine battery over the Leisure Batteries initially, due to the requirements of Stop/Start. This means that the Leisure Batteries voltage doesn't rise initially and maybe not for 10-20 minutes, but if a power hungry system is activated, heated seats, AirCon or headlights then the Leisure Batteries voltage rises to 14+ volts immediately.

 

[Loz]

You need to check the supply cable (black wire) to the relay to see if the control is failing or if it is steady, it might be the relay.
Also, check all earth connections.

 

[szczota81]

You need to check the supply cable (black wire) to the relay to see if the control is failing or if it is steady, it might be the relay.
Also, check all earth connections.

@Loz Can you describe how to do it?

 

[elplutonianodepluton]

Unfortunately not. But one week ago the situation began worst even. Now I have no leisure charging at all. Engine battery voltage looks good, 80A fuse is OK. But no charging.
Anyone have idea what can be wrong. I would like to replace relay 2D0 951 253B.
I expect that relay was damaged when during generator failure. Directly before generator failure, there was a lot of strange sound coming from relay which was switching all the time.
I will keep you inform.
@icic Do you have the same problem?

One year ago from the last reply, but just curious, what was the end of this story?