Here are the pieces and ratings. Also my measurements. Trying to figure what I am doing wrong on the math.


300 Watt Sine Wave Inverter
10-16vdc input range
120V - 300W output.


Cordless Tool Battery Chargers
1-85W
1-95W
1-50W

When I plug them into the house power I measure just about 1 Amp draw from each.

My math... 120V - 300W = 2.5Amp

So I was thinking if I plug the Inverter to 12V Batt. Which I did. Not being charged, just a free standing Batt.. I figured if I plugged two of those into the inverter I would be drawing near 2 Amps.

However, when I plugged just the 85W rated one in and put a battery on charge it only drew about 5.5Amps DC after a surge to about 7Amps DC. So it seems I could run two of those chargers well under 20 Amps from the battery.

What I wanted to figure out was circuit draw, wire size, fuse size, etc..

My problem is I'm doing something wrong DC Math side.

If I go to a calculator and use 12V - 85 Watts = 7 Amps, that makes sense, but that's for the battery charger. Does the inverter simply pass the wattage through? It is not marked for wattage draw.

It seems like to me Wattage from the Batt. Should be Inverter+Charger
I measured the Inverter ON at 0.2Amps DC so maybe it's just insignificant?

IIRC the Blue Sea fuse panels will take 30Amp fuses so it seems like this Inverter with maybe three chargers would still be plenty safe. I'll probably run two and then some lower power chargers for AA, Camera batts., a Laptop feed as well hopefully, etc..

So if my testing and reasoning is correct or close. It seems like I can build charging station off that 300W Inverter and run it off one 30Amp Blue Sea circuit with the correct sized wire for distance which will be very short.

Does anyone see anything wrong or dangerous with this?