Originally Posted by Titleguy
I didn't phrase my question right I guess. I was trying to get the math to work right in my head. The way I see it a 25 amp charger would use 120 volts, not the 12 you had stated earlier. So, wouldn't a 25 amp 120v charger be using 3000 watts? not the 300 stated earlier?
OK you just have to look at it one side at a time....
The OUTPUT of the charger is 12 volts and 25 amps so 12 x 25 = 300 watts.
On the INPUT side of the charger if you increase the volts by 10 times
to 120 volts you DEcrease the amps by the same factor of 10 and the
WATTS stay the same. 120 volts X 2.5 amps still = 300 watts.
The above example totally ignores heat losses in the charger as well as
the fact that a battery is usually charged at around 15 volts but my
statement still stands--
Even the smallest generator can power a 25 AMP OUTPUT battery charger.
The problem usually is the smallest cheapest generators are noisy.