I'd just buy a separate small charger.The thruster is only
operated intermitantly and a small charger should do the trick.
I have friends that have done the same with a LectraSan with
good results. The downside of having a separate battery is
that you are limited by the capacity of that battery. My thruster
draws about 80A but is connected using the heavy wire. I only
run it when the engine is running so power is not a limitation.
DOes the cost of a separate battery and charging system offset
the cost of the wire?

Doug
s/v Callista

"KNebulon" wrote in message
...
I wired up a new Lewmar 12v bow thruster and put a battery right next to
it to
minimize cable size. The boat has 4 pairs of 6v batteries all charged
with an
older Freedom 20 inverter/batt. charger with no separate float charge
output.
How can I charge the thruster batt. without it drawing from the ships
banks.
I'm thinking a batt. isolator won't work because the current flow is in
the
same direction. Any solutions? The boat is a 45 ft. 20yr. old Ferreti
sailboat with twin Mercedes diesels, a wiring challenge to say the least.

Thanks Ken