Inverter Cable

Tennesseahawk

Veteran Expediter
I have a 2000 watt inverter, which will be approx 15' away from the batteries. What gauge wire should I use? I was thinking 2 or 0.
 

RLENT

Veteran Expediter
I have a 2000 watt inverter, which will be approx 15' away from the batteries. What gauge wire should I use? I was thinking 2 or 0.
I'd be using 2/0 at a minimum (what I'm using on about 5' run, same size inverter) .... with that much length 4/0 would be better.
 

xiggi

Veteran Expediter
Owner/Operator
I'd be using 2/0 at a minimum (what I'm using on about 5' run, same size inverter) .... with that much length 4/0 would be better.

I was telling someone the other day how you used to post very helpful replies to sprinter questions. Nice to see you offering your thoughts again.
 

Tennesseahawk

Veteran Expediter
2/0 is so friggen huge. They use 4 with a 1500 watt usually. I'm only going to use this for a 1000 watt microwave and charging my puter.
 

RLENT

Veteran Expediter
2/0 is so friggen huge.
Yup, it is .... about as big a round as my thumb.

I used Cobra X-Flex 2/0 .... very finely stranded (1200+) and very flexible.

Cost around $135 for 35' .... the correct Panduit cable lugs for it cost about double that ($300+ .... but that was to wire everything, including the power from the engine and the entire battery bank)

When I bought it, it was done with the intention that it would outlast the vehicle and could be migrated to the next one. That is still the plan.

They use 4 with a 1500 watt usually. I'm only going to use this for a 1000 watt microwave and charging my puter.
You may be able to get by with less ....

Off the top of my head, I'd say that it's more critical on the charging side to the battery bank itself (for the health of the batteries, particularly depending on battery type) depending on your investment in batteries .... but it also factors into the voltage drop on equipment side .... which may affect the health/longevity of your inverter and connected equipment downstream.

There's some good info on wire ampacities and a voltage drop calculator the following link:

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies

On the above I would defer to Turtle, he helped me spec my setup out and really knows his stuff.
 
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Turtle

Administrator
Staff member
Retired Expediter
They use 4 with a 1500 watt usually.
Yeah, at four feet.

It's not about how much you actually draw through the inverter, but how many volts the inverter gets from the battery bank. If the volts at the inverter are consistently lower than what the battery is putting out (due to voltage drop for a given length of cable), the batteries will be overworked, as will the inverter. Neither will last as long as they could.

A 1000 Watt microwave, assuming that's not "cooking" Watts and is the actual amount of Watts the appliance draws, that's 92 amps (83.3 plus 10% for the inverter loss). If the computer draws 3 amps, that's 3.3 amps, plus the 83.3 is 86.6, let's call it 87 amps. Assuming nothing else is connected to the inverter or the batteries, you'll need 4/0 cable to keep the voltage drop below 0.15 volts (a little over 1% drop). 0.15 doesn't sound like much, and it's not if it's between the charging source and the battery bank, but it's about the maximum voltage loss you want between the battery and the inverter.

For a 2000 Watt inverter that might actually carry 2000 Watts (167 amps plus 10% is 183 amps) you'd need a cable that's just stupid thick, a 500 MCM, which is a 7.7/0 and .8 inches thick, nearly twice as thick as a 2/0 cable. 500 MCM FlexCable costs like $17 a foot, and you'll need to take out a loan for the proper lugs and the proper Class-T fuse block and fuse for it.

Have you heard about this nifty new invention called an "extension cord" where you can put the inverter within a few feet of the battery bank and then run an extension cord as long as you want, to wherever you want? 'Cause that same inverter 4 feet away can use 3 or 2 AWG cable for what you want to use it for, and 1/0 cable if you want to use all 2000 Watts, all while keeping the voltage drop to the appropriate level.

Rule is, when connecting the inverter to the battery use the thickest wire available, in the shortest length practical. Ideal length is 3-4 feet, with the maximum length generally recommended being 10 feet. But shorter is always better. If you need more length it is much better to put it on the AC side (with an extension cord from inverter to appliance) than on the DC side (with gnarly-thick cables). But, 15 feet may indeed be the shortest practical. Don't skimp on the cable, lugs or the fuses (Class-T for its arc-smothering capability). Keep the pictures of Bruno's flaming truck burned into your brain.
 

Tennesseahawk

Veteran Expediter
Unfortunately, it's about 12' from the batteries to where the inverter will be. After what Turtle says, I'm thinking 2/0. Does this sound right?
 

RLENT

Veteran Expediter
I'm thinking 4/0
Given the distance involved, I would concur.

I'm using 2/0 on about a 4' or 5' run feeding a 2000w AIMS Pure Sign Inverter.

My microwave would seem to be a similar size to 'Hawk's (it's a small Magic Chef) ..... and while I no longer run the microwave with the vehicle off as a matter of practice, I just went out and run the microwave for one minute with the vehicle off to gauge the inverter power draw.

The Xantrex Battery Monitor showed a draw from the battery bank ranging between 105A and 110A, with no other devices being powered (I unplugged the refrigerator/freezer, which could add another 8A to 10A IIRC, and the laptop charger, while plugged in, had nothing connected to it)

One thing to keep in mind is that if you are not running a pure or true sign-wave inverter, the run times on your microwave will roughly double.
 

purgoose10

Veteran Expediter
I'd be using 2/0 at a minimum (what I'm using on about 5' run, same size inverter) .... with that much length 4/0 would be better.

I run 2/0 on my C/Vans from the main battery back which is about 5-8 feet and the rest is 1/0. My TT I also use 2/0 as a main line. You need a cable that not only carrys the current with less restriction but one that doesn't create heat.
 

RLENT

Veteran Expediter
Depending on the wattage, but when he goes to pay for the 12' of 4/0 cable he'll probably pass out.
Heheheh .... yeah ....

I looked at the price of 4/0 cable after I concurred .... looks to be around $8/ft currently ....

Back when I bought the 2/0 (4+ years ago) it was a little under $4/ft (including shipping)

The lugs ain't cheap either .... fortunately, if all you are doing is running a pair of cables, you'll only need 4 ....
 

RLENT

Veteran Expediter
You need a cable that not only carrys the current with less restriction but one that doesn't create heat.
Yup ....

I put in a Sterling Alternator-powered Intelligent Battery Charger to charge the auxiliary bank. What it does is take the alternator output and and hold the voltage down (on the alternator side of the charger) to boost the amperage output of the alternator.

The unit then takes this feed and splits it, boosting the voltage internally on one leg (the charging current going to aux battery bank), leaving the other leg (charging current going to the starting battery) unboosted.

It's able to coax over 200A out of a 150A Bosch alternator (temperature dependent)

I don't recall offhand exactly what size cable I used from the alternator to the charger ... but it was a good bit larger than the stock cable that went from the alternator to the starting battery.

At any rate, it gets very, very warm when the unit is operating - you wouldn't want to hold onto it for long ....
 
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