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Mark Borgerson

In article ,
says...
In article ,
Mark Borgerson wrote:

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.)

Geez Louise, are all the folks in this NewsGroup math retards?

if you have 160 AH @ 12 Vdc that is 1920 WATTHours, NOT 1929 KWH...

Duh.... Your only off by three orders of magnitude....

Ooops, Sorry about that, The 1.920x10^3 WH on my HP Calculator
suffered a typo in transcription and became 1,920KWH.

I then managed to carry the K throughout the rest of the
calculations. DOH! I should know better than to try
such calculations before my morning caffeine dose!

It's good to see that someone is actually checking the
math.

At least I think I arrived at the proper conclusion----that
you only need to use about 133 Watts continuously to require
quite a large alternator to recharge your house bank in
4 hours. In tropical waters, you might reach that load on
refrigeration alone---particularly if you want ice in
your cocktails! ;-)

Mark Borgerson