The submarine USS Tiru (SS 416) had a battery bank of 126 cells which were
essentially 126 separate 1 ton batteries wired together externally.
However, the electricians were constantly monitoring each cell so a cell
that was going bad was identified in a timely manner and dealt with.

Should a Westy owner wire 2 batteries together and routinely monitor the
specific gravity of each cell there would be little chance of one battery
being a problem for the other.

Mike