"Capt. Neal®" wrote in message
...
Duh! the two batteries are in series. The one with the 12v tap cannot
become
more discharged than the one without because the battery without the tap
will charge the one with. Or the one with will discharge the one without
until they are both the same. This is the same thing that happens with
individual cells in a 12v battery. With two 12v batteries in a series one
simply has more cells in a series.

If you became familiar with the concept of batteries in series and batteries
in parallel, then come back and review your own reply.

Meindert