Originally Posted by MyronL
Plugged oxygen concentrator into Kill a watt plugged into wall AC last night. Display results this morning, 10 hours later:
- 3 KWH
- 124.5 volts
- fluctuating 260 to 2.89 amps output
- power factor fluctuating from .79 to .86
Is this right? 1000 x 3 = 3,000/124.5 = 24.09 amps
it is just the kwh divided by the hours to get the watts
3000 / 10 = 300
and the volts times amps comes up with the same answer
average amps 2.7 * 124 volts is 334 watts
so it must spend more time around 2.6 amps then 2.89.
mathmatically 300 watts / 124 volts = 2.4 amps
These are all with a 124 ac supply and that would probably be a 12v 400watt inverter running all night. So what would the inverter be sucking out of the 12v batteries?
I wonder what the 12volt units are using?
in real life...
The formula that I've seen thrown around is that inverters are 85% efficient and so
300 watts / .85 = 353
353 watts / 12volts = 29.4 amps
That would be per hour so the full ten hours would drain 294 amps from the batteries.
More than the capacity of the dual 6v system of 220 amps.
( the other formula that i've seen is
300watts / 12v * 1.1 = 27.5amp
its adding only %10 for inverter losses. )
But I really don't know if a modern day inverter uses what the 'common' formula says.
I'd like to have a trimetric meter installed so that I could measure the same as the Kill-a-Watt but on 12v dc systems.