# Inverter Question

Discussion in 'Homework Help' started by speedster239, Jul 3, 2010.

1. ### speedster239 Thread Starter New Member

Nov 24, 2009
12
0
If I have an inverter for my boat which allows me to produce 120v AC from 12v DC and I have a 120 watt lightbulb running after the power is inverted that means that 1 amp is flowing after the inversion. BUT, how much current is being drawn from the batteries themselves before the inversion?

Based on what I know I'd say since 120watts power is necessary to operate the bulb that would mean 12 volts/120 watts = 12 amps. That means the bulb is drawing 12 amps from the batteries themselves before the inversion? Is this correct or is my thinking completely flawed?

Thank you so much,
Vaughan

2. ### JoeJester AAC Fanatic!

Apr 26, 2005
3,909
1,738
I = P/E

The problem is you need to know the efficiency of your inverter to determine the current drawn from the battery. Assuming a 80% efficiency means the battery is providing 150 W so you can enjoy that 120 W light. Then P/E or 150/12 = 12.5 amps.