Wire sizing for inverter in small camper

McCarthy

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Chinese inverter that is being sold under different names, here an example:





At that price one would hope that they put some proper capacitors inside to handle inrush draw.


Fused with 100 Amps. Inputs for 4 AWG or 2 AWG, depending on cable lengths:

 

12VoltInstalls

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It isn't about book and code. It is about a competent, functional install. If installing 1Kw inverter is is simple common sense to wire it for 1 kW. I'd call that taking personal responsibility for the equipment you install
Not sure this is read or understood
“Wire for the equipment” is not an instruction as much as perhaps a principle, just like “fuse to protect the wire”
You can weld with 20V and 40A; not giving respect to low-volt electricity can result in injury or serious death.

nothing I’ve installed has ever caught fire
 

joepah

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Nice trailer and rig!

Even though you are safe with running two 4 AWG wires per terminal for 15 feet, the voltage drop is 0.4 volts at 1000 watts.. not good.

Per my wire combiner calculator, two 4 AWG cables are equivalent to a 1 AWG wire

1000 watts/12 volts = 85 amps... Voltage drop would be 0.4 volts

If it were me I'd keep the inverter close to the batteries and run an extension cord to an outlet where ever you need it.. Power losses a lot lower at 115 VAC.
 

PerryB67

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That renders his question and intent useless. I go by what people say and want, not by eventualities that may arise when somebody else hooks up more than he planned. As soon as we start treating everybody like a kid we are doomed to begin with. In reality we need to go back to personal responsibility and away from more regulations, code and laws.

If you want to stick to the book and code, most of the builds I have seen won't pass.
And that attitude is why many RV fires start because someone inadequately wired their inverter.

It's not just about you, but anyone who uses your RV in the future. That's one solid reason for code!

Perry
 

McCarthy

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And that attitude is why many RV fires start because someone inadequately wired their inverter.

It's not just about you, but anyone who uses your RV in the future. That's one solid reason for code!

Perry

As I said 2 times, one 4 AWG is enough for his setting.

Have fun installing 4/0 AWG in your rigs.
 

boondox

Chief Engineer, RedNeckTech Industries
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As I said 2 times, one 4 AWG is enough for his setting.

Have fun installing 4/0 AWG in your rigs.

Saying it twice doesn't make it a good idea. Wiring an inverter for less than half of its rated output just isn't wise. Nobody is talking about running 4/0. Believe it or not there is a place between too small and too big.
 

McCarthy

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Saying it twice doesn't make it a good idea. Wiring an inverter for less than half of its rated output just isn't wise. Nobody is talking about running 4/0. Believe it or not there is a place between too small and too big.

Your own linked calculator says it right there!

Allowable voltage drop 3%:


1633104773499.png




1633104781570.png



Now, average discharge V on LifePo4 cells is 3.2 V.

Vdisch-pt 3.2 V * 4 = 12.8 V

If you would use 12.8 instead of 12.0 volts, amps and resistance on wire would be even lower.

I have been working on electronics ever since I made my masters in Electronic Engineering back in the 90s, incl on such things like S-76s.

Really love Will's YT channel and his inspiration, but this forum is full with a bunch of hobbyists trying to tell people what to do. I think I'm done here for good.
 

boondox

Chief Engineer, RedNeckTech Industries
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Your own linked calculator says it right there!

Allowable voltage drop 3%:


View attachment 67122




View attachment 67123



Now, average discharge V on LifePo4 cells is 3.2 V.

Vdisch-pt 3.2 V * 4 = 12.8 V

If you would use 12.8 instead of 12.0 volts, amps and resistance on wire would be even lower.

I have been working on electronics ever since I made my masters in Electronic Engineering back in the 90s, incl on such things like S-76s.

Really love Will's YT channel and his inspiration, but this forum is full with a bunch of hobbyists trying to tell people what to do. I think I'm done here for good.

Just relax. Why can't we disagree without getting hot under the collar? I've been wrong so many times in my life I really don't get too worked up when I am wrong again.

The problem you are having is that the total distance is 30 feet, 15 there and 15 back. So you are getting 1/2 of the correct answer.
 

McCarthy

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Just relax. Why can't we disagree without getting hot under the collar? I've been wrong so many times in my life I really don't get too worked up when I am wrong again.

The problem you are having is that the total distance is 30 feet, 15 there and 15 back. So you are getting 1/2 of the correct answer.

You are kidding, right!? You don't double the resistance / lengths of any wire just because there is ANOTHER cable for negative. Could be chassis ground, would be the same thing. The source of energy is on one end, the consumption happens on the other end, and there are 15 feet between those 2 points, not 30!
 

boondox

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You are kidding, right!? You don't double the resistance / lengths of any wire just because there is ANOTHER cable for negative. Could be chassis ground, would be the same thing. The source of energy is on one end, the consumption happens on the other end, and there are 15 feet between those 2 points, not 30!

Nope, not kidding. It is the total run the determines resistance. Using chassis ground is another bad idea for high amp loads but even if you do it adds resistance. I personally would always run both positive and negative wires for inverter installation. All the professional installs I have ever seen do the same thing. So yes, it does wind up at 30 feet of wire.
 

McCarthy

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Nope, not kidding. It is the total run the determines resistance. Using chassis ground is another bad idea for high amp loads but even if you do it adds resistance. I personally would always run both positive and negative wires for inverter installation. All the professional installs I have ever seen do the same thing. So yes, it does wind up at 30 feet of wire.

You are going on my ignore list, buddy, for spreading false information and sticking to BS.
 

boondox

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You are going on my ignore list, buddy, for spreading false information and sticking to BS.


I'm sorry, but it is true. There are 30 feet of wire in the circuit. So 30 feet of wire need to be accounted for. Some calculators specify one way distance, in which case they add the second run. Some, like the Blue Sea ask you to put in the total length.
 

chrisski

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At this point, we seem like we are just stating the same beliefs over and over again hoping someone else will change. This thread is derailed. The OP will not likely get anything useful.

I am dropping out. For others, the UNWATCH is at the top right of the screen.
 

boondox

Chief Engineer, RedNeckTech Industries
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While it has gone OT there is a vital point here. It is important to know that when calculating voltage drop that both conductors need to be accounted for. Some calculator ask for 1 way length, some for both directions. In either case it is accounted for. This isn't a belief, that is simple physics.
 
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