Why did I buy 2AWG battery cables for my inverter?

[Sean Steele]

smoothJoey, I don't remember the exact chart now but I just clicked the link to bay marine in your first reply and entered my parameters. 2 AWG is at the bottom of the results but still <3% for voltage drop.

 

[John Frum]

smoothJoey, I don't remember the exact chart now but I just clicked the link to bay marine in your first reply and entered my parameters. 2 AWG is at the bottom of the results but still <3% for voltage drop.

Voltage drop, got it.

 

[Sean Steele]

Are you saying I shouldn't use that reference for ampacity?

 

[John Frum]

Are you saying I shouldn't use that reference for ampacity?

The ampacity tables are below.
That calculator is for voltage drop.
You need to consider both.
And you should multiply your max ampacity by 1.25 for fuse headroom.

 

[Sean Steele]

I see 210 for single conductor 2AWG. The Anderson connector I'm using is only rated for 175 and the BMS should shut down at 175. To my mind, 2AWG is good enough. Am I reading/interpreting something incorrectly?

 

[Supervstech]

The 4awg internal copper with high temp insulation is also inside a fan cooled free air space. So heat is dissipated, and the insulation can take more heat than is generally used on feeder wiring to the inverter.
2AWG is fine as long as you don’t load the inverter to the max often.
if you plan on running it more than 1/2 load over an hour, I would use 1/0 cable...

 

[Sean Steele]

Biggest load that will run for extended periods is my tv and blu-ray player. Otherwise short bursts charging laptops and cell phones or long runs of a small fan.

 

[Supervstech]

Biggest load that will run for extended periods is my tv and blu-ray player. Otherwise short bursts charging laptops and cell phones or long runs of a small fan.

Pfft... for that, you would be fine with #8 wire...

 

[Supervstech]

It is all about watts in use.

most tv’s use less than 50 watts now... ditto the players... say a max of 300W... that’s around 25A for your short burst loads...
12 could handle it without much trouble.

 

[Dzl]

By the aybc chart I linked 1 awg is indicated.
4/0 by nec.

ABYC and NEC ampacity charts are pretty well harmonized I think. Are you sure you are referencing tables for similar conditions and wire insulation temperature ratings?

the wires in the inverter can be small due to length..

But ampacity is independent of length, yes? At a minimum the wire used must be off a high enough ampacity to handle the max continuous load, regardless of length. At least that is my understanding.

Voltage drop, got it.

Are you saying I shouldn't use that reference for ampacity?

That is the baymarinesupply.com calculator, and I'm almost positive it accounts for both Voltage Drop and Ampacity.

It doesn't explicitly indicate ampacity, but I believe it will not give results that exceed the wire ampacity. You can confirm this by playing around with really short wire lengths and high current, it will only recommend wire with a high enough ampacity even though the voltage drop #'s are really really low. This is in contrast to many other calculators that only account for Vdrop. Example:

* Its worth noting this calculator assumes 105*C wire and 30*C ambient temperature, if these values are different it is necessary to derate

 

[orangeminnie]

The most important thing is to size the wiring to the fuse you intend to use. For 2000W, something around a 250A fuse is usually recommend, at which point most charts recommend 4/0, even for a short run.

 

[John Frum]

ABYC and NEC ampacity charts are pretty well harmonized I think. Are you sure you are referencing tables for similar conditions and wire insulation temperature ratings?

Nope.
I thought ABYC was just 105C and NEC is 60, 75 and 90C.
I see now that I've been laboring under a misapprehension.
I just found this https://diysolarforum.com/media/abyc-ampacity-chart-single-conductors.7/

That is the baymarinesupply.com calculator, and I'm almost positive it accounts for both Voltage Drop and Ampacity.

You are correct again, see above.
Thanks for setting me straight.

 

[sshibly]

Watch my fav Quebecois test 10 awg wire at 100amps
I need that bench load tester he has, any ideas what that is? lol

 

[Sean Steele]

The most important thing is to size the wiring to the fuse you intend to use. For 2000W, something around a 250A fuse is usually recommend, at which point most charts recommend 4/0, even for a short run.

See, now this sounds backwards to me. I would think you would chose the wire to handle max amps and then fuse to protect the wire.

 

[orangeminnie]

See, now this sounds backwards to me. I would think you would chose the wire to handle max amps and then fuse to protect the wire.

I agree, except for special cases like this: Consider a 2000W inverter. The maximum continuous amps might be 190A, but the recommended fuse might be 250A. The run is short, so voltage drop is not an issue. How do you size the wire? My point is that in limited cases like this where there is a recommended fuse size, the process is inverted. Pun intended

 

[Sean Steele]

Ok. So let's apply this to a 2000W inverter. The maximum continuous amps might be 190A, but the recommended fuse might be 250A. The run is short, so voltage drop is not an issue. How do you size the wire? My point is that in limited cases like this where there is a recommended fuse size, the process is inverted. Pun intended

My inverter has a recommend wire size but no fuse size. Since I went with 2AWG which is supposed to be good for 210 Amps, I figured on installing a 200A fuse. Of course, this is contrary to the *1.25 rule that most apply for fuse headroom. My inverter is 2000W. It's surge rating is 4000 for 40 milliseconds. The circuit I am powering, built in ATS, is protected by a 15A breaker on the AC side and the inverters AC bypass is 2000W.

My BMS is supposed to cut off at 175A output but we all know they go over that rating for a short time. The battery has an internal fuse of 300. With my meager understanding, 200A fuse protects the wire while still allowing for some surge, 2400watts. All of these watts are calculated at 12v but the battery will normally be operating between 13 and 14 so, slightly less amps to make the same Watts.

I'm fine with popping a fuse once in a while, I just want to make sure my wires and equipment are protected. Is my logic flawed?

 

[John Frum]

My inverter has a recommend wire size but no fuse size.

What is the recommended wire size?

Since I went with 2AWG which is supposed to be good for 210 Amps, I figured on installing a 200A fuse. Of course, this is contrary to the *1.25 rule that most apply for fuse headroom. My inverter is 2000W. It's surge rating is 4000 for 40 milliseconds.

40 milliseconds is ~2 cycles of 60hz alternating current and can therefore be ignored as insignificant.

I'm fine with popping a fuse once in a while, I just want to make sure my wires and equipment are protected. Is my logic flawed?

If you are ok with popping fuses from time to time you should be fine

 

[orangeminnie]

My inverter has a recommend wire size but no fuse size. Since I went with 2AWG which is supposed to be good for 210 Amps, I figured on installing a 200A fuse. Of course, this is contrary to the *1.25 rule that most apply for fuse headroom. My inverter is 2000W. It's surge rating is 4000 for 40 milliseconds. The circuit I am powering, built in ATS, is protected by a 15A breaker on the AC side and the inverters AC bypass is 2000W.

My BMS is supposed to cut off at 175A output but we all know they go over that rating for a short time. The battery has an internal fuse of 300. With my meager understanding, 200A fuse protects the wire while still allowing for some surge, 2400watts. All of these watts are calculated at 12v but the battery will normally be operating between 13 and 14 so, slightly less amps to make the same Watts.

I'm fine with popping a fuse once in a while, I just want to make sure my wires and equipment are protected. Is my logic flawed?

For 90dg C insulation, I'm seeing maximum 130A for #2 wire. For 60dg C insulation, it's only 90A. The attached charts may be conservative, but they have served me well, as a guide.

 

[Sean Steele]

What is the recommended wire size?

"2AWG or larger"

 

[Sean Steele]

For 90dg C insulation, I'm seeing maximum 130A for #2 wire. For 60dg C insulation, it's only 90A. The attached charts may be conservative, but they have served me well, as a guide.

The 2AWG I bought from BatteryCablesUSA is 105C.