# Power required for battery charger (1 Viewer)

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#### Ivory55

##### Free Member
what size generator would you need to power a stand alone battery charger for 350 amp battery bank using something like c tek 300 to 500 amp charger. Cheers

#### pappajohn

LIFE MEMBER
300amp to 500amp.... Typo?... A large arc welder runs at a couple of hundred amps.

30 to 50amp maybe but even that sounds big.

It depends on the chargers input watts, not the output amps.
You would only need a very small genny.
A 600watt 2 stroke would be more than sufficient but noisy.

#### TheBig1

Deceased RIP
honda eu10i nice and quiet and 1kw output should suffice

#### Minxy

LIFE MEMBER
300amp to 500amp.... Typo?... A large arc welder runs at a couple of hundred amps.
I suspect it wasn't a misquote ... I hear he's a descendant of 'Dr Frankenstein'!

OP
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#### Ivory55

##### Free Member
I just wondered if it would charge the batteries quicker then the standard Sargent charger so the generator would need run for so long. Cheers

#### autorouter

To find the maximum recommended charge current for 350 amp-hours of battery capacity, just divide by 5, so that's 70 amps.

If they are discharged to 50%, then you will need to put back 350/2 = 175 amp-hours. At 70amps, that's 175/70 =2.5 hours. At 50 amps it's 175/50 = 3.5 hours. In reality add at least an hour, because the charger slows down after 80% full.

I don't know what the Sargent charger rate is, but I guess it's less than 50 amps.

OP
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#### Ivory55

##### Free Member
Think it’s 20amp hour charger.

#### autorouter

To find the power required, first find the amps output of the charger. Then multiply by 12 (volts) to get the power output. For example, a 20 amp charger will be outputting 20 x 12 = 240 watts.

Then add about 10 or 20 percent for efficiency losses. For this example that's 24 or 48 watts. so a generator with an output of 300 watts will be OK for this job.

Downside is, at 20 amps it will take 175/20 = 8.5 hours to charge up the batteries from 50%.

If it's 50 amps, that's 600 watts, so a 750 watt generator will be OK. As above, that will take 3.5 hours.

#### pappajohn

LIFE MEMBER

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