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Mark Borgerson

In article ,
says...
Wayne.B wrote in
:

The most practical alternative in my opinion
is to drive a sine wave inverter with a high current alternator. This
has a number of advantages starting with extra battery charging
capability, the use of standard/easily repaired/replaced components,
and fewer appendages on the engine. I'm doing this on my trawler to
save generator usage while underway. It is important to size the
alternator very generously since most will not develop rated current
for more than a short period of time. Also important is to use large
cables (at least #2) between the alternator and inverter, and to use
multiple belts to drive the alternator. Single belts will not hold up
very long delivering more than 70 or 80 amps.

I don't think it will be very long before some smart builder tosses
caution to the wind and simply buys the rights to use hybrid technology
from the cars. Unlike the cars, the boats have room and lifting power
for much larger capacity batteries than the little hybrid cars, say
buried into the keel for ballast, instead of topside where they
shouldn't be. Lithium Polymer batteries really require no maintenance
so the battery packs can simply be installed and left for many years,
same as in the cars with much tougher use.

The battery pack in our Prius puts out 350V. I'm not sure I want
to pay for the engineering to make that reliable in the marine
environment. High voltages and salt water on a small boat---
that makes me nervous.

Propulsion for the boat will simply be part of the boat's overall power
system, high voltage traction motors as the cars are using with
electronic controls and automatic engine start/stop as needed for
maximum efficiency. The prime mover will be a high voltage
alternator/rectifier. Saildrive traction motors will also be used as
recharging alternators while underway under sail to supplement the prime
mover, reducing runtime and fuel usage.

Being a high voltage DC system, not this old nonsense 12/24/48VDC from
the 1940's charging lead-acid beasts, the weight of many of the
components will be offset by using small, high voltage wiring in the
boat, instead of these huge battery cables, monstrous contactors and
current, current, CURRENT. 10A at 400VDC = 4000 watts of serious power,
not 138 watts like a 12V system. 10A can easily be switched by a wide
variety of solid state devices that don't even get warm and use
negligible power. High voltage switching AC power supplies running off
the high voltage bus will provide 115/230 50/60 Hz AC to power
appliances and a new range of boat electronics that will run off the AC
bus at sea and simply switch to the shore bus at the dock. 12VDC/24VDC
appliances will be soon phased out as relics of the past.

Boats will, probably, be equipped with twin engines and twin traction
motor/alternators for redundancy made from much smaller prime movers.
Because the prime mover is now running an AVERAGE load, it no longer
needs to produce a peak takeoff power. The battery supplies, just like
the cars, will provide peak power. Engines will run with more constant
loads at maximum fuel efficiency under computer control. If one engine
or traction motor system fails, the other mover simply runs both
traction systems at reduced average power until repairs are made,
automatically cross connecting in the redundant systems. At anchor,
both engines may run to operate heavy loads, dropping automatically to
one as the batteries become charged and loads drop. When batteries
become charged, the engine will be stopped by the computer until the
batteries are drained down and require charging again. How long they
are off is up to the boat owner and his loading. The computer will
handle the discharging/recharging with no input from the humans. This
will eliminate the supercharging, overcharging, undercharging, and crazy
ideas incompetent owners have tortured battery systems with since the
first 6V car battery out of the old Chevy was brought aboard for a
light.

IIRC, Batteries in hybrid cards (at least the NIMH batteries in the
Prius) stay in the 70 to 90% of full charge range to prolong lifetime.
That system will need a lot of work to be useful for long runs
without engine recharge.

Mark Borgerson