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Old 08-29-2016, 08:29 PM   #1
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Cable size for inverter

Can anybody tell me what size battery cables I would need for a 1000 watt inverter with a run less than 15'?
I figured I would be pulling about 83 amps at 1000 watts. Most of the time I would only be using 300 watts or less.
And yes I will be installing an inline circuit breaker close to the batteries.
My plan is to install this inverter for the 120 volt circuit for the TV and my Blue Ray player so we can keep our grand children busy while driving.
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Old 08-30-2016, 06:08 AM   #2
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Move the inverter as close as possible to the battery.

At 1000 watts, you'll be drawing 83 amps from the battery.

#2 would be a good size. ALSO - Do not rely on a chassis for your return, you need to use #2 cable in both directions.

If you moved the inverter closer to the battery, say 2-3 feet from the battery, you may be able to get by with #4.

I installed a 1500 watt inverter in my Ole Toyhouse.

1500 watt Inverter Install - Improvement and Do-It-Yourself Projects you have done to Share! - Toyota Motorhome Discussion Board

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Old 08-31-2016, 01:15 AM   #3
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I disagree. I prefer to have as little loss as possible <1%.

1/0 gauge wire is what I would use.
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Old 08-31-2016, 05:57 AM   #4
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Put it in the power bay and use the #6 that the converter uses to reach the battery. If it is a PD unit there are extra lugs to attach a daisy chain. The #6 is ok for the amperage and since you will almost always use it with the alternator running and at 30 amps or so you should be fine. On my 335 I have it that way and it has never shut down for low voltage, including chargers, 2 CPAPs, and TVS when parked OVERNIGHT!
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Old 08-31-2016, 06:37 AM   #5
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I did a few calculations to show what the voltage loose in the wire would be. This is based on drawing 100 amps, and shows a 30 ft run (15 ft in each direction) and a 4 ft run (2 feet in each direction)

DO NOT rely on the chassis for your return, You MUST use a wire for the plus and the minus.


Wire ___ 30 ft___ 4 ft
#6 ____ 1.372 __ 0.183
#4 ____ 0.732 __ 0.098
#2 ____ 0.457 __ 0.061
#1 ____ 0.366 __ 0.049
#1/0 __ 0.284 __ 0.038
#2/0 __ 0.229 __ 0.030
#4/0 __ 0.146 __ 0.020

I don't have any recommendations on what would be an acceptable voltage drop... To me, anything less than 1/4 volt would be OK, but the cost of wire is certainly a factor.

Based on my 1/4 volt loose in the wire, you would need to move the inverter closer to the battery so the wires aren't as long, or go to larger cable to keep the voltage loose down to an acceptable number.

Cable is expensive and may cost as much as your inverter.
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Old 08-31-2016, 08:49 AM   #6
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I took a different approach that any of the above mentioned. I bought a 12volt inverter off the shelf that plugs into the cigarette lighter. It supports 5 amps needed to run some medical equipment while driving. Also use it to power up the tv, haven't added a blue ray but you get the idea. No problems after 5 years doing this and it runs off the engine battery and alternator. Didn't want to go the other route for an occasional use item.


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Old 08-31-2016, 10:27 AM   #7
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Quote:
Originally Posted by wrapperman View Post
Can anybody tell me what size battery cables I would need for a 1000 watt inverter with a run less than 15'?
I figured I would be pulling about 83 amps at 1000 watts. Most of the time I would only be using 300 watts or less.
And yes I will be installing an inline circuit breaker close to the batteries.
My plan is to install this inverter for the 120 volt circuit for the TV and my Blue Ray player so we can keep our grand children busy while driving.
mmm I think a 1000 watt inverter only produces 10 amps not 83. I installed a 900 watt inverter in my van camper and it produces 9 amps. This easily operates a mini frig and tv. I also run a small microwave but turn the other appliances off when microwave is on. I use a heavy duty extension cord with a 4 gang outlet to power all of them. The guage is about the same as house wiring but multiple strand copper for flexability. You don't need heavy cable to carry 10 amps of output. My 900 watt inverter has a standard 3 prong outlet to plug the extension cord into. Also the supply cables from the battery to the inverter are the same guage as my heavy duty extension cord and are also stranded. My battery is right next to the inverter. I use a long run of red battery cable from my engine battery to the deep cycle battery in my van. The ground wire to this battery is grounded to the van frame and is a short black cable. The house battery charges whenever the motor runs but I also have an isolation switch if I don't want to draw down the starter battery. The house battery can also serve as a boost to the starter battery if needed if the isolation switch is turned to on and the house battery is fully charged, When dry camping I turn the isolation switch to off so the starter battery does not draw down.
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Old 08-31-2016, 10:38 AM   #8
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mmm I think a 1000 watt inverter only produces 10 amps not 83. I installed a 900 watt inverter in my van camper and it produces 9 amps. This easily operates a mini frig and tv. I also run a small microwave but turn the other appliances off when microwave is on. I use a heavy duty extension cord with a 4 gang outlet to power all of them. The guage is about the same as house wiring but multiple strand copper for flexability. You don't need heavy cable to carry 10 amps of output. My 900 watt inverter has a standard 3 prong outlet to plug the extension cord into.
Amps an inverter draws -vs- amps an inverter produces are two different things.
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Old 08-31-2016, 11:25 AM   #9
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Amps an inverter draws -vs- amps an inverter produces are two different things.

True. And if he meant draw down from the battery he needs to allow for about 98 amps instead of 83. The inverter looses efficiency mostly due to resistance and heat generated. The actual battery draw down is 1000 divided by 12 = 83 divided by .85 = 98 amps. If the inverter is located very close to the battery you don't need very heavy wire. There are size charts available online.
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Old 08-31-2016, 04:12 PM   #10
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Amps an inverter draws -vs- amps an inverter produces are two different things.
Correct. And for simplified planning, figure BY A MULTIPLE OF TEN. Figure 1000 watts at a probable actual 115 vac is 8.7 amps. Figure with minimal loss, and some inverters ARE NOT very efficient,. That will be 82 to 87 amps draw on the batteries. Hour and a half at full load (that would be a coffee maker or very small heater or little tiny microwave, -- you blow through the useful output of two golf cart batteries. Yer not apt to do that so made the AC run long and get the inverter right near the batteries. Then the manufacturer recommendation of 4ga or up it to 2ga and be OK. You will never be happy with the voltage loss at a 15 ft run for the DC.
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