John Weston wrote:
Dennis Pogson, in article 5fbYf.4574$ic1.1629@newsfe5-
win.ntli.net, says...

I would have divided the 3000watts (AC) by 120 Volts (AC), not 12
volts.

That size of inverter at 12 volts will need a nominal 25amps when
drawing max power. Add on say 15% for loss on conversion and you
would be looking at near enough 30amps.

Personally, for that sort of current draw I would be looking for
about 500A/H batteries and massive section cabling dependant on how
close to the inverter you can locate the batteries.

You need to properly work out the likely maximum draw before working
the figures for required battery power.

Deep-cycle truck batteries are worth a look. Don't buy starter
batteries for this type of application.


Dennis. Watts = Volts x Amps

Watts is power so you need the same power out as into the
inverter plus any losses in the inverters circuits. You can't
get more power out than you put in.

So 3000W = 12V x 250A or 120V x 25A I make it you'll need
250A (plus) at 12V into the inverter to get 3000W out

Does that mean that the 300-watt inverter I use to (occasionally) power 2
laptops is taking 25 amps out of my batteries? Must check that cigar-lighter
fuse!