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Mark Borgerson

In article 529e2675-f8de-4c10-b09c-9b2bedc19cb6@
29g2000prb.googlegroups.com, says...

err... you house is 110 VAC and the boat is 12 VDC. Your 200 amp load
center is handling 110 X 200 = 22 KW (approximately) while the boat is
handling 12 X 250 = 3 KW.

Cheers,

Bruce

Hello Bruce:

Yes you and et al are totally correct. I aplogize deeply for my quick
read of the original post and mislead reply. After 4 beers and a
quick look at his post I though the guy was going to hang an AC 110V
generator off his main. So at face value of my post I must apologize
for a seemingly ignorant rant. But to be honest most the times the
problems guys here seek guidance are off on the wrong foot to begin
which leads them down a path of frustration, expense, loss of
reliability, added complexity, and compromised safety.

Time for me to cross my legs and ask for that last spike. Crucify away
gentle men, I am guilty of not giving a member of RBC a sincere read.

Even still............. do you actually believe a boat 45' should
consume that many amp/watts ??? I still say that its either time he
reduced his amp consumption or get a larger vessel capable of
providing the volume to support that kind of load,,, as in a dedicated
gen set.

Based on my experiences in some of the inlets of British Columbia, I
would greatly prefer cruisers to have the alternator and battery
capacity to avoid running a generator while at anchor.

I try to practice what I preach. On a 21-day cruise this summer from
Ketchikan to Bellingham, we only used the genset to charge the
house batteries about 3 times. We didn't watch TV or use the microwave
too often---except the night the propane tank ran out. ;-) (Propane is
hard to find between Desolation Sound and Nanaimo.)

We also had the benefit of quite long daily runs to get the
house battery charged. It was the days where we ran only 3 or 4 hours
that required the most attention to power management.

If you look at a worst-case short cruise as four hours of engine time,
then you can charge at 200A for 4 hours. That will put about
160AH back into your batteries for later use.

160AH x 12V = 1,920KWH.

From that, you have to subtract running loads---which can be
considerable if you have the radar and chart plotter on
for four hours.

Let's say you have 1600KWH in the battery bank to keep you
going for the 20 hours the engine is not running.

In the summer, you may be up and about for 12 hours
in addition to the running time.

1500KWH/12 = 133 Watts per hour.

125 Watts isn't a lot if you're going to recharge all your
portable electronics and keep the sounder on for comfort's
sake. (We probable keep the depth sounder on more often in
the Northwest with 20+ foot tidal ranges.)

Investing a thousand dollars or so in LED interior lights
is probably the best way to cut the AH budget. After all
each of the old-style incandescant lamps was about 15-20 Watts.
Reasonable cabin lights alone could be 150 Watts.

Mark Borgerson

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