Two batteries and the engine alternator is charging one, possible?

[yossarian]

S339 is your cube fuse.

You can proceed by checking continuity (resistance) between the marked points.

I would start with a continuity check between chassis ground and points C and D. This checks your shunt as the path from C, D to the chassis ground is through the shunt [N162].

If those are ok probe the voltage between chassis ground and A B and E

As you can see it's a very simple system.

Edit: A24 is the wardrobe battery. A1 is the underseat battery.

Edit2: If you probe and see 12.7 V the path to the rear battery is intact (but might be high resistance). If you probe and see 11.4V your path to the underseat battery is intact (but might be high resistance).

With what we're seeing you look to have an open circuit (broken wire or something disconnected) somewhere.

Edit3: Added note about shunt in step 1.

 

[ThomasHJ]

One last question folks....

Could a kind of faulty shunt be related to this?

@elplutonianodepluton I'm going to do something really stupid here. I'm going to suggest checking the earth shunt. Even though @WelshGas ruled it out and he's probably right, but...

Do your batteries seem to run out of juce quickly according to the control panel? We thought for a while that we were running on just 1 leisure battery because according to the control panel, the voltage seemed to go down (too) fast. Checked the cube fuse, measured the voltage of the batteries directly, etc. In reality the batteries were just fine and the earth shunt problem was causing the faulty readings on the control panel.

VW Camper Centrum here in NL fixed the earth shunt problem (We have a T5 and it had not been done by the previous owner) and after that all was fine again.

As said, @WelshGas is probably right, but consider checking this old thread about the problem we had.

 

[elplutonianodepluton]

@elplutonianodepluton I'm going to do something really stupid here. I'm going to suggest checking the earth shunt. Even though @WelshGas ruled it out and he's probably right, but...

Do your batteries seem to run out of juce quickly according to the control panel? We thought for a while that we were running on just 1 leisure battery because according to the control panel, the voltage seemed to go down (too) fast. Checked the cube fuse, measured the voltage of the batteries directly, etc. In reality the batteries were just fine and the earth shunt problem was causing the faulty readings on the control panel.

VW Camper Centrum here in NL fixed the earth shunt problem (We have a T5 and it had not been done by the previous owner) and after that all was fine again.

As said, @WelshGas is probably right, but consider checking this old thread about the problem we had.

Hey there! Thanks for the answers. That thread you mentioned was my go-to reference when I decided to change my leisure batteries before embarking on my road trip. It's also where I learned how to check the cube fuse the first time before posting here.

As for the shunt, my concern is that I'll have to disassemble everything to access it. It's located beneath the freezer, which is secured under the kitchen. The kitchen has a gas installation, and the whole setup seems like a nightmare for me. Unfortunately, I don't have clear instructions on how to tackle this task, so it's going to take me some time to work through it all. It might be a while before I can provide more feedback on the situation.

 

[yossarian]

Hey there! Thanks for the answers. That thread you mentioned was my go-to reference when I decided to change my leisure batteries before embarking on my road trip. It's also where I learned how to check the cube fuse the first time before posting here.

As for the shunt, my concern is that I'll have to disassemble everything to access it. It's located beneath the freezer, which is secured under the kitchen. The kitchen has a gas installation, and the whole setup seems like a nightmare for me. Unfortunately, I don't have clear instructions on how to tackle this task, so it's going to take me some time to work through it all. It might be a while before I can provide more feedback on the situation.

I would test the shunt before disassembling the van. There is a comprehensive shunt replacement guide in resources.

 

[elplutonianodepluton]

View attachment 115146

S339 is your cube fuse.

You can proceed by checking continuity (resistance) between the marked points.

I would start with a continuity check between chassis ground and points C and D. This checks your shunt as the path from C, D to the chassis ground is through the shunt [N162].

If those are ok probe the voltage between chassis ground and A B and E

As you can see it's a very simple system.

Edit: A24 is the wardrobe battery. A1 is the underseat battery.

Edit2: If you probe and see 12.7 V the path to the rear battery is intact (but might be high resistance). If you probe and see 11.4V your path to the underseat battery is intact (but might be high resistance).

With what we're seeing you look to have an open circuit (broken wire or something disconnected) somewhere.

Edit3: Added note about shunt in step 1.

Wow! The help you're providing is truly incredible.

Your troubleshooting guide with the check points is fantastic, but I'll need to return home and go through all these points properly.

Once again, thank you for taking the time to write that guide.... clap clap clap thank u

 

[elplutonianodepluton]

I would now move onto checking the Earth ( -tve ) connection for the rear battery, as going by your Volt readings the rear battery is not connected in parallel.

If you remove the +tve lead from the rear battery, what voltage do you measure between the detached lead and Earth ( use the battery clamp bolt ) and the detached lead and -tve pole of the rear battery?

Pending for the next pit stop without raining. Today is raining here. Thank you !

 

[elplutonianodepluton]

I would test the shunt before disassembling the van. There is a comprehensive shunt replacement guide in resources.

Mmm.... shunt test without disassembling.....I don't know if that is possible.... is it? I will try to take a look ....thx once again.

 

[Sp0_0k]

Connected in parallel the 2 batteries will be treated as one and both will discharge at the same rate.
Problems of balancing the discharge arise when the 2 batteries are of dissimilar size or type.

Actually you can use different capacity for parallel connection.

 

[Sp0_0k]

Need to test both batteries separately. One can easily be almost dead and still sit parallel simply not accepting charge due to high internal resistance.
Perfect test is full cycle discharge-charge.
More simple just measure internal resistance of each.
Even more simply use cheap battery condition tester. Works similar to internal resistance measure by applying load and measuring voltage drop.
All methods require them disconnected from each other.

 

[WelshGas]

Actually you can use different capacity for parallel connection.

True , but the California with 2 leisure batteries is designed and setup to use 2 x similar leisure batteries rather than 2 x dissimilar batteries in parallel.

 

[WelshGas]

Need to test both batteries separately. One can easily be almost dead and still sit parallel simply not accepting charge due to high internal resistance.
Perfect test is full cycle discharge-charge.
More simple just measure internal resistance of each.
Even more simply use cheap battery condition tester. Works similar to internal resistance measure by applying load and measuring voltage drop.
All methods require them disconnected from each other.

The exact scenario that I had, with 1 battery charging but failing to hold a charge when tested individually.

 

[Sp0_0k]

True , but the California with 2 leisure batteries is designed and setup to use 2 x similar leisure batteries rather than 2 x dissimilar batteries in parallel.

They have nothing designed. They just put 2 batteries in parallel that work according to laws of physics. If you put 2 same AGM batteries one 75ah and another 105ah. You will just have more capacity. Bigger one will accept more current on charge and give more current on discharge.

When you have 1 battery failed as a topic starter has it litterally means he has 10ah and 75ah batteries in parallel that can keep working fine.

Buying same rated batteries will never give you exact same capacity and even IR.

 

[WelshGas]

They have nothing designed. They just put 2 batteries in parallel that work according to laws of physics. If you put 2 same AGM batteries one 75ah and another 105ah. You will just have more capacity. Bigger one will accept more current on charge and give more current on discharge.

When you have 1 battery failed as a topic starter has it litterally means he has 10ah and 75ah batteries in parallel that can keep working fine.

Buying same rated batteries will never give you exact same capacity and even IR.

That may well be true in the California Beach, which has no centralised Control Panel or battery monitoring capability.

 

[bvddobb]

I'm going to do something really stupid here. I'm going to suggest checking the earth shunt. Even though @WelshGas ruled it out and he's probably right, but...

I would second this approach! When the earth shunt is faulty (broken, not well grounded), the Control Unit gets faulty input, and then gives wrong output and takes wrong 'decisions', understandably. It can give all kind of weird, hard to understand issues with your electrical system.

For us, it started with the parking heater shutting off in the middle of cold nights when we were not on electric hook-up. We also went through all the steps of checking batteries, block fuse, etc. All to no avail.
Only when we fixed the earth shunt grounding (using the available kit) the CU started 'behaving' again: showing somewhat more accurate readings, not unnecessarily shutting off the heater, etc.

P.S: for those on the continent, interested in the earth shunt kit: the German Caliboard sells it as wel. For us on the continent a lot cheaper without expensive shipping, customs issues, duties, etc. than ordering from the UK, since Brexit.

 

[elplutonianodepluton]

FIXED! (Some months ago)

After all this time and with the solution working for months, I have decided to come and share my final solution.

In my case, there were two issues.

1- One of the new batteries (new!) was not working properly. One drained much faster than the other one. The only way I found to identify this was by purchasing a new battery. After more than a month of testing, I was certain. All working ok just replacing it.

2- The battery in the engine was old and also had problems. I am certain that this affects the system when the circuit is closed with the motor contact and the alternator starts charging. If the motor battery is not in good condition, it will not charge the other batteries properly. In fact the other batteries drain faster some seconds before the alternator starts to fill the engine battery. I noticed this as soon as I installed the new battery in the motor, because it no longer happens.

If these two points can be useful to your troubleshooting guide... Yeah.

I would like to express my gratitude to everyone for their helpful trial and error suggestions. Your input was truly valuable and I want to extend my sincere thanks.