You do raise some interesting points, though I don't think any of them are even
close to the downside of an extra battery. For instance, you still need a
fairly large wire run to deal with, though not 1/0. And how do you prevent that
from melting if it ends up carrying the windlass load. BTW, all windlass
connections should be through an appropriate breaker, and should be turned off
when not used - you certainly don't want to start the windlass going if you're
stumbling around the foredeck and trip on a switch! Scorching should not be a
possibility in any proper setup.

The house bank won't get run down (hopefully) because its monitored by an
AmpHour meter, and since the odds are high one will be powering for at least a
few minutes before or after setting or hauling, there should be not problem. A
dedicated battery could have a problem that goes un-noticed until total failure.
If spiking is a concern, the windlass could be wired not to the house bank, but
to the starter battery.


"DSK" wrote in message
...
Jeff Morris wrote:
I never bought the logic, neither did my builder, who used the "long wire"
approach.

IMHO there are benefits to both approaches, but to choose one over the
other, you need to do some careful math.


Consider, for a 80 foot round trip and an 80 Amp load, you want "2" gauge
wire
for a 10% loss.

I think that's a bit on the light side. Most charts only show wire run
lengths up to 60' and a medium size windlass is going to be a 100 amp
load anyway.

A 10% voltage drop is significant. Might knock other things off line,
especially any digital devices. I'd prefer to size things for a lower
voltage drop anyway, where practical.


... Being conservative, you might go to "0" gauge. That 80 feet
weighs 35 pounds. So the result is you would put a 35 pound starting
battery in
the bow instead of distributing 35 pounds along the length.
And we're not
talking about all the complications of keeping an extra battery charged and
happy. The only virtue is that you now have some redundancy in a critical
area.
But you also have another failure mode.

Either way you go, yo have another failure mode possible. If there is a
short somewhere along the 80' wiring run, the lack of resistance will
kill your whole battery bank really quick, and possibly leave scorch marks.


There are other issues, like how do you prevent 80 amps from going down the
charger wire if you raise the anchor when the engine is running? And if you
don't keep up with the use, how large a battery to you need to ensure you
have
the juice to reset the anchor several times, the last time, of course, in
the
middle of the night?

Well, how do you insure that your house bank isn't drained by resetting
the anchor in the middle of the night? How do you feel about sawing
holes in bulkheads to run two passes of #0 cable (or bigger) with
looming of course? How about running that big a load to ground and
putting back voltage spike on everything else in your 12V system?

There are plusses and minusses to both running cable and putting in a
dedicated windlass battery. IMHO Ray's case is just over the edge where
it looks like a good case for a dedicated windlass battery.

Fresh Breezes- Doug King