On Mon, 06 Oct 2003 04:41:29 GMT, "John Tretick"
wrote:

Hello Group,
+
I have a 24" Bayliner Cierra 2001 and I am interested in using AC when not
at port. No place to install a generator, so I'm thinking an invertor with
a batterstore. Possibly increasing my batteries to 3 and wiring in GFI
circiut to power mixers, inflators , hairdriers, etc.. when I'm anchored.
Northern tools sells a sealed Marine invertor for 399 its 3000/1500W which
works for my purposes.. doubt it would run the AC..
but I guess I'd have to get a larger on for that..

Has anyone installed this redundant power source defore? I'm curious how
long you can run on it without depleting one battery..
Actually thinking about installing a third battery for this purpose.

Thaks,

John

You can use an inverter to power small AC loads for fairly long
periods, or large loads (like a microwave or electric kettle) for
short periods. If you have a 1200 watt 120 V load such as a kettle,
it will draw 10 amps at 120 volts, but the inverter will draw a little
over 100 amps from the batteries to produce that power.

A Group 27 battery (about 25% larger than a traditional car battery)
would be rated about 110 amp-hours, if I recall correctly, but that
rating assumes the battery is discharged over 20 hours, which would be
a draw of only 5 amps. Drawing 100 amps, you will likely only get
around 50% capacity, so you could only run your kettle for about 30
minutes before the battery is completely discharged.

To determine the battery capacity you need, you will have to look at
the likely AC loads you will want to use, and the length of time you
will use each one, to compute the total amp-hours required per day.

You will also have to make some provision to recharge the batteries -
this will require a high capacity battery charger, and probably an
upgrade of the alternator and regulator on the engine, if you expect
to be away from shore power for more than a day or two.

You should also re-arrange the batteries so that one battery is
dedicated to engine starting, and can't be discharged by the inverter
or other "house" loads.


--
Peter Bennett, VE7CEI
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