i have a 600 w invertor to power a tv and dvd player. it will be about 10 ft from the battery.

What size wiring do I need? i have an 80 amp fuse for the hot side.

Chris,

I am assuming this is a "portable" inverter with a single NEMA 5-15R receptacle on it. As such, it needs to be mounted within cord's reach of the devices it powers (TV and DVD). By contrast, a hard-wire inverter could be mounted closer to the batteries and you could get by with running much smaller wire on the 120VAC side with lower overall loss. I am further assuming this is a 12-volt model, and not 24. If either of these is incorrect, please chime in.

600 watts continuous probably implies a 1,000 or even 1,200 watt "surge" rating, but you should check this against the written specs. 1,200 watts at 12 volts is 100 amps, which is pretty significant current.

Since you are using an 80-amp fuse, though, you can size the wires for that amount of current as a maximum.

The size wire you need will depend on the wire and insulation type, but for most stranded copper wire with thermoplastic insulation, 80 amps requires a minimum of #4 for temperatures to 75°C (157°F).

At 10' one-way distance, 80 amps on #4 will have a voltage drop of nearly half a volt and well over 3%, generally considered unacceptable. However, the continuous rating of the device is 600 watts, or 50 amps, and likely you will usually be drawing even less. 50 amps on #4 produces a drop of just 1.7%, considered acceptable.

So the short answer is #4 THWN or THHN, available at most home improvement stores. Note that #4 is extremely thick and unwieldy, so plan accordingly. Also, #4 will probably not fit the lugs (or whatever connection you have) on the little inverter, so you will probably have to transition to something else to make the connection.

600 watt ? does that not come with a cigarett lighter plug?electrical guys will chime in but for that size a #10 wire should be over kill but safe...#10 is good for 30 amps at 120 volts...

Yes, but it's not 120 volts, it's 12 volts, and 80 amps as stated in the original question. So, no, #10 is not sufficient (but it would be for a 600-watt, 120VAC circuit). Also, a cigarette lighter is not capable of 80 amps; generally, the lighter-plug inverters are 100-150 watts max.

This is an excellent opportunity to try my hand at guessing. The wire size is determined by the amperage, so 600w @ 120v output would be 5 amps and a 50 amp input at 12v. According to the below link, you could get by with #12 in and 22 out. The chart does not say so, but it implies the 120 v figures are for AC and the 12v figures are for DC. Actually, I would have guessed a larger input wire than a #12. Proctors, what's my score?

http://www.rowand.net/shop/tech/wirecapacitychart.htmYour score is low, sorry

In fact, your "gut" was right in this instance (where you said you would have "guessed" larger). Specifically, the note above the table you linked says

*"This chart is a simple 'max capacity' chart for a short wire run."* Later he writes

*"The values here for 12V usage are not yet certified to be correct/valid/safe."* In fact, the capacities listed are for uninsulated conductors in "free air," a condition that only exists theoretically, or for overhead power lines. Insulated conductors in real applications follow much stricter rules.

This is one reason I urge caution when surfing the 'net to find this information. A quick survey of five search results for "ampacity" yields five

*different* sets of recommendations.

I would play it safe and upsize to #10 or even #8. Inverters don't like voltage drop.

Correct on the voltage drop, but way too small on the wire gauge. #4 is called for, and I would certainly not go lower than #6.

i say #6 72 cents a foot at h/depot

You win the prize for closest. #6 is good for 65 amps in THWN or 75 amps in THHN. This wire size could definitely be used, but I would recommend in this case replacing the 80-amp fuse with one rated 65 amps max.

HTH,

-Sean

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