Battery bank / inverter ratio

[amiklic1]

I need info about batteries working with voltage inverters.

Let's say I got 500 Ah battery bank in 12V, and I got 1000 W voltage inverter      12V > 220 V.

How can I calculate the amperage that's being pulled out of a batteries if the inverter is working in full power ( 1000 watts ) or let's say 300 watts?

[johnlm]

Wattage out=Wattage In/Effieciency

So if you are pulling 1000 watts on the output and lets say the effeciency of the inverter is 90% (0.90) then the wattage in (from the battery) is 1000W/0.9=1111 Watts.

Since the input voltage is 12V the current from the battery is 1111 Watts/12 V =92.6 Amps.

At 300 W on the output the input wattage is 333 Watts and the curent from the battery is 27.8 Amps.

Read up on Ohms Law and the Power Law to understand all the above.

Johnlm

[Zix]

You can calulate the current from the link below.A rule of thumb to figure in your head is a bit more than 10 times the AMPS at 12 volts than it is at 120 volts(approx).

Hope this helps

http://www.angelfire.com/pa/baconbacon/page2.html

Zix------------------------

[nothing to lose]

Yes,

Watts divided by volts equals amps.

For most things I figure that's close enough or add a few extra amps to cover the losses the inverter and wires have.

If I know the amps of a device at 120Vac then I multiplie that by 10 an add a few extra.

So if a frig uses 7.5amps at 120Vac, I figure 7.5amps X 10 =75amps from 12V battery bank and maybe 5-10 extra for the inverter. Or I may use 11 instead of 10 when I multieply. For a 7.5amp frig then I would likely round to 80amps.

It's pretty simple and easy to do in your head fast that way if you have 12V batterybanks, if you use 24V instead then divide that 80amps above by 2 and it's 40 amps, or if you have 48V banks divide by 4 and it's around 20amps.

Still the same wattage though.

Depends how precise you want to figure it.