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Here are some basics for use with your inverter.
The first thing to do is to determine the
efficiency of the inverter. This figure will be
listed in the inverter documentation. Whatever it
says, subtract 10%, so if it claims 85% efficiency
(you are spending 15% of the power just to run the
inverter) make your calculations using 75%
instead. Now, remember that watts are a measure of
power, so at first there is no conversion, just
take the efficiency, don't forget that extra 10%,
and calculate the power required to drive the
load.
So if you are powering a 1000 watt device with an
inverter that claims to be 85% efficient your
batteries need to produce 1250 watts.
Now we do the conversion. Watts equals volts
times amps. We know the watts and the volts so we
divide the watts by the volts (1250/12) to get the
amps. In this case 109.66 amps.
Since you NEVER want to discharge ANY battery
below 50% you can see that to run that device for
just 1 hour you need at least a battery/battery
bank with 220 amp-hour capacity.
As you can se, inverters eat batteries very
quickly, so either use it very sparingly or get
yourself a HUGE battery bank!
Eric Thompson
S/V Procrastinator
South San Francisco
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