x2 12 volt batteries in Canter

How are they being charged?

Is it an after market additional battery, is one of the batteries an auxiliary that runs things like a fridge, etc.

Is it the main battery that discharges or the auxiliary?

It sounds like you are using 12v from one battery of the vehicles 24v system. By doing this you will flatten/wreck the battery involved as it will never be charged correctly.
To allow the use of 12v accessories on a 24v vehicle there are a few ways to do it correctly.
For very small loads a 24v to 12v transformer while inefficient can be an easy solution.
A better way is to use a Charge Equaliser which floats the batteries at the same potential allowing 12v to be drawn from either one or both batteries.
The current thinking is to use a switch mode power supply to provide 12v from the vehicles 24v system.
companies like Redarc or GSL make both charge equalisers and switch mode supplies.

If as you say it's always position "B" and never position "A" even when the batteries are swapped over, then I believe the battery in position "B" must have some accessories attached to it that is not attached to the battery in position "A" ??

Maîneÿ . . .

whot state are you in morry

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