4/0 wire to inverter getting hot

corn18 · Thursday at 10:06 AM

So I doubled up my 4/0 wire from the batteries to the Lynx distributor and they stay ambient now even at 325A. The single 4/0 wire to the inverter (3 ft total run) is getting hot at max load. Not super hot, but warmer than I would like. Would love to double it up but the MPII 12V 3000 lugs will not accept two 4/0 lugs without modification. Best I can do is 2/0 x 2. I would much rather just shave one mm off the side of the 4/0 lugs and double up the 4/0 cable vs. running 2 x 2/0.

This is what 2 4/0 lugs look like on the MPII:

SparkyJJO · Thursday at 10:16 AM

I'm the crazy idiot who would shave the edges of the lugs slightly so they fit.

OzSolar · Thursday at 10:25 AM

corn18 said:
Not super hot, but warmer than I would like.

What's the voltage drop from the Lynx to the Inverter at full load? Voltage drop from the battery to the Lynx?

That will tell us a lot.

Brucey · Thursday at 10:29 AM

SparkyJJO said:
I'm the crazy idiot who would shave the edges of the lugs slightly so they fit.

I would shave a fair bit from both so they arent putting any pressure on those blue components on the left.

corn18 · Thursday at 10:42 AM

SparkyJJO said:
I'm the crazy idiot who would shave the edges of the lugs slightly so they fit.

I'm not sure how crazy it is. The contact area on the Lynx Distributor is just the size of the nut under the lug. Even after some modification, the contact area on the MPII would be a lot larger. Always bugged me that the contact area on the Lynx was so small for the positive lugs. The negative lugs contact directly to the bus bar. The top of the mega fuse does as well. But not the output lug.

Suijkerbuijk · Thursday at 11:11 AM

Somting like this ??
Is this a solution for you ?

Quattrohead · Thursday at 11:37 AM

Measure the voltage drop and that will tell us a lot. How warm is warm? And what is the type/rating of the cables.

corn18 · Thursday at 11:41 AM

Quattrohead said:
Measure the voltage drop and that will tell us a lot. How warm is warm? And what is the type/rating of the cables.

I'll have to measure it next time I am out there.

Cables are 4/0 welding cables and lugs from Windy Nation rated 105C.

ksmithaz1 · Thursday at 4:32 PM

Grind off the sides and roll with it, or find a different lug. They make the latter, sometimes the price is not right, usually it will be a tad thicker. The amount of material you remove is not going to be that significant, and at any rate you will be maximizing the surface contact to the conductor. The screw lugs on the post above would work as well. It will likely separate into two fins once you grind off the edges. A compromise but a reasonable one.

DPC · Thursday at 4:57 PM

corn18 said:
Not super hot, but warmer than I would like.

It is the nature of electricity that things get warm when in use.
If you can keep your had on it without discomfort then your OK.
Hot spots are something to watch for however.

DougfromdaUP · Thursday at 5:04 PM

Are those 5/16 screws? It looks like an awful lot of clearance. I’d try a 5/16 lug.

seneysolar · Thursday at 6:47 PM

corn18 said:
So I doubled up my 4/0 wire from the batteries to the Lynx distributor and they stay ambient now even at 325A. The single 4/0 wire to the inverter (3 ft total run) is getting hot at max load. Not super hot, but warmer than I would like. Would love to double it up but the MPII 12V 3000 lugs will not accept two 4/0 lugs without modification. Best I can do is 2/0 x 2. I would much rather just shave one mm off the side of the 4/0 lugs and double up the 4/0 cable vs. running 2 x 2/0.

This is what 2 4/0 lugs look like on the MPII:
View attachment 225040

These might fit better side by side.

Panduit lugs

They offer "narrow tongue" versions

JBoffgrid2022 · Thursday at 7:18 PM

DPC said:
It is the nature of electricity that things get warm when in use.
If you can keep your had on it without discomfort then your OK.
Hot spots are something to watch for however.

You could go grab a temperature gun at Home Depot and that would give you a good read on the surface temp.

k490 · Thursday at 7:49 PM

Another good option is the FLIR camera for for smart phones. They are about $200 but you can see hotspots easier.

OzSolar · Thursday at 7:50 PM

It's too bad no one's mentioned checking for voltage drop, the easiest possible test you could in just a few seconds with a $30 DVM,

corn18 · Thursday at 7:55 PM

I have a Fluke MM, a laser temp thingy and a FLIR. When I sober up, I will use them to gather data. Might be a few days. I just drunk ordered Taco Bell.

OzSolar · Thursday at 8:00 PM

corn18 said:
I have a Fluke MM, a laser temp thingy and a FLIR. When I sober up, I will use them to gather data. Might be a few days. I just drunk ordered Taco Bell.

The smartest thing anyone's said on this thread so far.

HarryN · Friday at 10:57 AM

High temperature cables just means that the insulation can handle running at higher temps. This allows more current to flow through the same copper cross section (with more power loss ) and "deal with" the cables running hotter.

Don't take this as criticism, but people tend to under estimate just how difficult and perfect things have to be to really make a 4 / 0 crimp that is really optimal. The really pro shops wake up each morning and qual everything by make some and cutting them open to inspect vs just assuming that life is ok.

For substantial cables, I use battery cables usa, but there are a number of places that make good quality cables. I have seen a couple of them on ebay - but I don't buy anything from ebay or amazon.

Quality Copper Battery Cables Made in the USA! - BatteryCablesUSA

www.batterycablesusa.com

0truck0 · Friday at 11:45 AM

325 amps? this is a vehicle?

Aluminum lugs for copper wire? Why not get copper lugs?
not an issue at all to file down the lugs so they fit in that tight spot.
Could you just put both wires into one big lug and bolt on once? err, I guess that would make working on it hard.
Looks like they both touch the same plate. OR double stack them?

Minimoose · Friday at 11:57 AM

corn18 said:
So I doubled up my 4/0 wire from the batteries to the Lynx distributor and they stay ambient now even at 325A. The single 4/0 wire to the inverter (3 ft total run) is getting hot at max load. Not super hot, but warmer than I would like. Would love to double it up but the MPII 12V 3000 lugs will not accept two 4/0 lugs without modification. Best I can do is 2/0 x 2. I would much rather just shave one mm off the side of the 4/0 lugs and double up the 4/0 cable vs. running 2 x 2/0.

This is what 2 4/0 lugs look like on the MPII:
View attachment 225040

Couldn't you just slightly oval the holes to spread them enough? Seems you would still get full contact pressure

SparkyJJO · Friday at 1:03 PM

So, did 8 people like my post because they like the idea of shaving the edges of the lugs, or did they like my post because they agree that I'm a crazy idiot?

rhino · Friday at 1:08 PM

Is there not enough room to reverse the first lug and then place the other lug on top?

Q-Dog · Friday at 1:15 PM

Have you tried to fit 4 pieces of 4/0 into the inverter's cable slot?

seneysolar · Friday at 1:16 PM

SparkyJJO said:
So, did 8 people like my post because they like the idea of shaving the edges of the lugs, or did they like my post because they agree that I'm a crazy idiot?

View attachment 225178

If i was working in a remote location and needed to make it work, trimming the edges would suffice just fine.
If doing this at home with all resources at hand, id spend $30 and get the narrow Panduit lugs so my OCD would settle down.

seneysolar · Friday at 1:21 PM

Q-Dog said:
Have you tried to fit 4 pieces of 4/0 into the inverter's cable slot?

Good point. If i recall its a tight fit. The 2nd negative doesn't make a strait shot out the hole in case.

4/0 wire to inverter getting hot

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