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Old 02-29-2012, 04:42 PM   #11
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Quote:
Originally Posted by Titleguy View Post
Is that a 12v charger or a 120?
Watts don't care.
If you are charging a 12 Volt battery with a charger that has a max output
of 25 amps on the battery side my math is correct.

The charger would appear as a 300-400 watt load on the generator.

The generator would be putting out 120 volts at 300 watts (ignoring
losses) so it would be producing 120 volts at about 2.5 amps.

The charger would be converting the 120 volt AC to 12v DC and both would
still be about 300 watts.

Some generators have 12v outputs but they are typically limited to
10 amps or less.
It's faster and more efficient to use a charger plugged into the AC outlet
on the generator.
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Old 02-29-2012, 04:51 PM   #12
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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?
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Old 02-29-2012, 10:31 PM   #13
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Converting Watts to Amps

The conversion of Watts to Amps at fixed voltage is governed by the equation Amps = Watts/Volts

For example 12 watts/12 volts = 1 amp
Converting Amps to Watts

The conversion of Amps to Watts at fixed voltage is governed by the equation Watts = Amps x Volts

For example 1 amp * 110 volts = 110 watts

Converting Watts to Volts

The conversion of Watts to Volts at fixed amperage is governed by the equation Volts = Watts/Amps

For example 100 watts/10 amps = 10 volts

Converting Volts to Watts

The conversion of Volts to Watts at fixed amperage is governed by the equation Watts = Amps x Volts

For example 1.5 amps * 12 volts = 18 watts

Converting Volts to Amps at fixed wattage

The conversion of Volts to Amps if the wattage is known is governed by the equations Amps = Watts/Volts

For example 120 watts/110 volts = 1.09 amps

Converting Amps to Volts at fixed wattage

The conversion of Amps to Volts if the wattage is know is governed by the equation Volts = Watts/Amps

For Example, 48 watts / 12 Amps = 4 Volts

Converting Volts to Amps at a fixed resistance

If you know the volts and the load of the resistance the amps are found by Ohm's law: Amps = Volts / Resistance

Converting Amps to Volts at fixed resistance

If you know the amps and the resistance Ohm's law becomes Volts = Amps * Resistance
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Old 02-29-2012, 10:49 PM   #14
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RubenZ hook a drill up to that Weed trimmer change the male plug to a female plug and you will get a low wattage genny.
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Old 03-01-2012, 07:46 AM   #15
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Quote:
Originally Posted by Titleguy View Post
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.

OR

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.
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Old 03-01-2012, 10:43 AM   #16
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Quote:
Originally Posted by caper View Post
RubenZ hook a drill up to that Weed trimmer change the male plug to a female plug and you will get a low wattage genny.
Check this out!! muddymuddymuddmann's Channel - YouTube
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