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

[elplutonianodepluton]

Hello!!!

I have a 2006 VW California T5 with two leisure batteries installed. I recently replaced these batteries because the previous ones had the same issue. I'm wondering if there could be any scenarios where both batteries are correctly connected in parallel for consumption but only one of them gets charged from the engine alternator? I just replaced both batteries yesterday.

A brain storm about it is welcome

Thank you folks!

 

[temporarysecretary]

First thing to check would be the continuity of the fuse on the positive terminal on the rear battery.

Search for cube fuse and you will see quite a few threads

 

[elplutonianodepluton]

First thing to check would be the continuity of the fuse on the positive terminal on the rear battery.

Search for cube fuse and you will see quite a few threads

Thank you for the quick answer. I did it before asking. It works. I can make again other double checking..... but I think it is ok.

 

[WelshGas]

Thank you for the quick answer. I did it before asking. It works. I can make again other double checking..... but I think it is ok.

Check with a Multimeter, not just visually.

 

[yossarian]

if there could be any scenarios where both batteries are correctly connected in parallel for consumption but only one of them gets charged

Only possible if the connection between them has failed. The part that is designed to fail is the cube fuse.

 

[elplutonianodepluton]

Allow me a couple of questions that provide a different perspective on the initial question:

With the batteries in parallel, both with the same charge, and the refrigerator running, what is the likelihood that one battery ends up more discharged than the other?

If that were to happen, could you please explain whether one battery acts as a resistor for the other, potentially leaving both completely discharged, or does one battery replenish the other, effectively balancing their charge? (The latest may seem similar question, but it's not the same.)

 

[WelshGas]

Allow me a couple of questions that provide a different perspective on the initial question:

With the batteries in parallel, both with the same charge, and the refrigerator running, what is the likelihood that one battery ends up more discharged than the other?

If that were to happen, could you please explain whether one battery acts as a resistor for the other, potentially leaving both completely discharged, or does one battery replenish the other, effectively balancing their charge? (The latest may seem similar question, but it's not the same.)

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.

 

[Ting Tong]

Allow me a couple of questions that provide a different perspective on the initial question:

With the batteries in parallel, both with the same charge, and the refrigerator running, what is the likelihood that one battery ends up more discharged than the other?

If that were to happen, could you please explain whether one battery acts as a resistor for the other, potentially leaving both completely discharged, or does one battery replenish the other, effectively balancing their charge? (The latest may seem similar question, but it's not the same.)

If they are identical batteries, the charge in both should deplete equally when connected in parallel. The fridge will draw 50% of its current from each one. The voltage across both should also be equal. If it isn’t, then a) your cube fuse is blown, b) the cable connecting the batteries is shot or c) you have a bad earth on the one with the highest voltage.

 

[elplutonianodepluton]

If they are identical batteries, the charge in both should deplete equally when connected in parallel. The fridge will draw 50% of its current from each one. The voltage across both should also be equal. If it isn’t, then a) your cube fuse is blown, b) the cable connecting the batteries is shot or c) you have a bad earth on the one with the highest voltage.

Thank you to everybody... I 'm going to recheck everything one more time

 

[elplutonianodepluton]

One last question folks....

Could a kind of faulty shunt be related to this?

 

[WelshGas]

One last question folks....

Could a kind of faulty shunt be related to this?

Not something I've heard of in relation to the Earth Shunt. Common symptoms are related more to high current draw in relation to Parking Heater start up with accompanying flickering of habitation area lights .

What exactly are the symptoms you are experiencing?

 

[elplutonianodepluton]

Not something I've heard of in relation to the Earth Shunt. Common symptoms are related more to high current draw in relation to Parking Heater start up with accompanying flickering of habitation area lights .

What exactly are the symptoms you are experiencing?

It's more or less the initial issue, thx for asking:

Both batteries are brand new and identical. And I changed the previous ones due to this.

I've noticed that the front seat battery tends to discharge more quickly and doesn't charge properly, while the rear battery remains more charged and operates without any issues.


Thank you in advance for your help folks!

Ps: no new tests. Still pending.

 

[pluc99]

How did you measure the respective battery charge levels for each?

 

[elplutonianodepluton]

How did you measure the respective battery charge levels for each?

I have three simultaneous voltage meters: one is connected to the shunt (original vw meter), which I believe is roughly halfway through the circuit. Another one is directly connected to the seat battery and reads the same voltage as the shunt. The third meter is provided by the solar converter connected to the rear battery terminals (the solar panel is disconnected). I've verified the values at the battery terminals (multimeter) and they match the readings on the meters.

 

[elplutonianodepluton]

Right now!

 

[yossarian]

Two words: Cube fuse.

See posts 2,4,5.

1. Your two batteries are not connected together
2. The part that is designed to fail is the cube fuse.

If you still are having problems detail your cube fuse test procedure. It's almost certain you are doing something wrong.

 

[yossarian]

And if you replace the fuse without charging the under seat battery it is possible to blow the replacement.

 

[dspuk]

What is causing your near 4 amp draw? You should be testing in circumstances where there is no draw I would say.

 

[elplutonianodepluton]

Two words: Cube fuse.

See posts 2,4,5.

1. Your two batteries are not connected together
2. The part that is designed to fail is the cube fuse.

If you still are having problems detail your cube fuse test procedure. It's almost certain you are doing something wrong.

It's all clear to me. I understand I need to double-check the cube fuse, as the second (4th,5...) comment suggested. I sense a bit of annoyance in your text-tone, but rest assured, I've got a grasp of the explanation, and I genuinely appreciate your timely responses. I was just responding to some questions and gathering more context. Your assistance and perspective have been invaluable to me. I'm currently on the road, and I'll need to make a longer stop to recheck everything thoroughly. Thanks again. Please don't worry or feel bothered by my inquiries. I'll return with more feedback or to share the final outcome.

 

[elplutonianodepluton]

What is causing your near 4 amp draw? You should be testing in circumstances where there is no draw I would say.

I'm currently on the road, and what I'm observing isn't a formal test at the moment.

 

[elplutonianodepluton]

And if you replace the fuse without charging the under seat battery it is possible to blow the replacement.

Oh, excellent point! Hmm...I am on the road now so I'll attempt to charge only the seat battery by disconnecting everything else and see if the alternator works solely with that one. Does it make sense for you?

 

[pluc99]

I have three simultaneous voltage meters: one is connected to the shunt (original vw meter), which I believe is roughly halfway through the circuit. Another one is directly connected to the seat battery and reads the same voltage as the shunt. The third meter is provided by the solar converter connected to the rear battery terminals (the solar panel is disconnected). I've verified the values at the battery terminals (multimeter) and they match the readings on the meters.

You hadn't mentioned solar before. Would the following explain what you're seeing? 1) The alternator isn't charging the front leisure battery (blown fuse, bad connection?) and 2) the connection between the 2 leisure batteries is broken (cube fuse?). Therefore the only charge you are getting is to the rear battery via the solar.

 

[elplutonianodepluton]

Two words: Cube fuse.

See posts 2,4,5.

1. Your two batteries are not connected together
2. The part that is designed to fail is the cube fuse.

If you still are having problems detail your cube fuse test procedure. It's almost certain you are doing something wrong.

Right now, I'm making my second pit stop with the goal of ensuring whether the cube fuse is still intact or not (I had checked it before).

Resistance 00.2

That was the easiest route. Thank you, everyone, for your time and patience. It appears I'll have to search for the issue elsewhere.

 

[elplutonianodepluton]

You hadn't mentioned solar before. Would the following explain what you're seeing? 1) The alternator isn't charging the front leisure battery (blown fuse, bad connection?) and 2) the connection between the 2 leisure batteries is broken (cube fuse?). Therefore the only charge you are getting is to the rear battery via the solar.

Hehe... ChatGPT is top... indeed...That's how it seems... but the cube fuse is all good (check the upper message). Thanks for your answers and your time.

 

[WelshGas]

Hehe... ChatGPT is top... indeed...That's how it seems... but the cube fuse is all good (check the upper message). Thanks for your answers and your time.

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?