Originally Posted by pattersonb
First question: Even though the inverter is rated for 3000 watts continuous, will it only supply whatever the device is demanding (i.e. 1200 watts, 10 amps, 120 volts)? I understand that this impacts battery drain, cable sizing, etc. Second question: The inverter manual says to use 1/0 (zero gauge?) for the connection to the battery. Is this overkill?
Here is my answer:
1) 3000 watts is its rating, it will only supply what the device you plug in requires.
2) What size wire you use depends on how much of the 3000 watts you want to use at any given time AND FUSE THE WIRE accordingly.
Since if you actually tried to use the entire 3000 watts your OEM battery would last about 10 minutes, my guess is you won't ever need that much.
So, suppose you only need 1200 watts of that inverter's capability. 1200 watts at 10 volts (the point at which your inverter will shut down and stop pulling juice from the battery) would require 1200/10 = 120 amps. The absolute minimum sized wire for 150 amps is #8 @ 12VDC although most folks (including me) will recommend no smaller than #4 Wire Capacity Chart
MAKE SURE you put the correct size FUSE in the line to limit current draw to the size wire you use and maximum anticipated amperage draw at 10 volts. You might be tempted to use 12 but don't. 10 volts is worst case.
Your inverter has a continuous wattage of 3000 but it has a peak wattage much higher (Say 3400 watts). At 3400 watts and 10 volts, your inverter is going to try and draw 340 amps from your battery. To handle 340 amps, your wire will definitely be a minimum of 1 or 0. (Your battery would melt into a puddle if it was possible to deliver that kind of amperage)
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