T&T: Inverter calculations

[capteric36]

 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
capteric36 at sbcglobal.net