My 2/0 cables are getting hot

[Carl Boyd]

Hello, 4 of my 2/0 cables gets warm to hot like 80 degrees or so, even blew the 300amp anl fuse. The 2/0 cable from the battery positive to the battery cutoff switch
doesn't even get warm, cutoff switch doesn't get hot. The 2/0 cable from the negative busbar to the inverter get pretty warm but from the negative side of the battery
to the busbar doesn't. The inverter get pretty warm like 80-90 degrees also but I'm not sure how hot they get normaly.
I have 600ah of batteries and 800 watts of solar 400w on each controller, 1 has 4 renogy 100w panels series/parallel the other has 2 200w hightec panels in series.
I haven't tried turning off the solar (not that is should matter, I think) and use the inverter and batteries to see if the cables still gets hot.
The inverter it's self has 2 grounding wires hooked to it a 10 gauge and even a 6 gauge battery cable. None of the other cables even get close to warm.
The setup is for a 50amp RV, the 3 wire output of the inverter is running to a 50amp transfer switch on the generator side and hot leg 1 is jumpered to hot leg 2.
The transfer switch doesn't seem any hotter on the generator than the shore power side. I'm not running any a/c's or big amp draws at the same time or anything but
after a few hours the cables get hot and the anl fuse smells like it's burning. Is the 300amp anl fuse too small, I ordered a few 300amp anl fuses and even
an extra 400amp fuse also. Does anyone have any ideas why only those 4 cables and fuse gets hot???
Thank You!!!

 

[chrisski]

There’s a couple types of ANL fuses. Cheaper audio fuses and a little more expensive ABYC rated fuses for main battery protection. Do you have the ABYC fuse?

I can’t tell from the pic, but does the wiring have fuse to lug contact without a washer between them?

The busbars also look like a 250 amp brass busbar, which if true would not be my choice for a 12 volt 3000 watt inverter. First because brass is not the best conductor, and second at max output could be close to or exceed 250 amps.

I used 4/0 on a 12 volt system with a 200 amp ANL fuse and never saw any heating by touch or IR thermometer on my inverter or wiring or lug or busbar.

For me a 300 amp fuse blowing on 2/0 wire is worrisome and going to a 400 amp fuse seems like a bad idea based off ampacity of the wire 2/0 wire.

 

[eXodus]

When you got two identical sized cables in series and one getting hot and one doesn't - I would suspect bad crimps. Or bad connections where they are connected.

Since cooper is a good heat conductor it could be that it radiates from on terminal up into the cable.

The busbars also look like a 250 amp brass busbar,

That could be the issue - it looks like all warm cables are connected to those bus bars. The red identical sized cable from the battery to the cutoff switch is not warm.

 

[corn18]

When I first installed my Victron MPII 12/3000, I was using 2/0 wire bigger buss bars. The wire running from the buss bar to the MPII would get hot. I swapped everything out for 4/0 cable and it is all cool, even @ 300A.

Some issues I see in your setup:

T-Tocas circuit breakers - junk. There are many videos showing how they heat up and don't work. Replace them with Bussmann or Blue Sea circuit breakers.

Buss bars - They look like cheap Amazon crap. I had similar ones rated for 250A and they were a lot larger than yours. Can't tell with the covers on, but they look undersized for your application. Replace with 600A Blue Sea or a Victron Distributor. The nice thing about using a Victron Distributor is you can get rid of all the other circuit breakers.

Cheap disconnect - can't tell the brand name, but again, get a Blue Sea disconnect.

ANL fuse - replace with a class T

Buss Bars -

Remeber, you are basically running a welder here. 3000W inverter can pull 400A. I know you said they heat up with no load, but that is scary. If you put a 3000W load on that inverter, you may burn something up.

This is my setup that is similar to yours.

 

[Bluedog225]

you guys have the best pics/diagrams. Gotta figure out how to do that.

 

[corn18]

you guys have the best pics/diagrams. Gotta figure out how to do that.

I just use PowerPoint. I download an image of the stuff I have from the interweb and then just connect the dots.

 

[chrisski]

A couple more comments:

-I agree with the battery disconnect switch comment. For a smaller project, I have the one in the OPs photo and that is rated at either 250 amps or 275 amps at 12 votls, and half that at 24 votls, and half that at 48 volts. I use it for a 24 volt project that I planned no more than 40 amps out of it, but I really only push 15 amps. I actually cringe when I see this in a n RV or house system.

-How did you make the crimps? I have a manual hydraulic crimped I use for up to 4/0 cable, rated for more, but I don’t want to go thicker. I‘ve seen hammer crimps and soldering as a cheaper way, but in a power application where the amps are running high all the time, not so good. May be OK in an automotive application, but not a power application.

-I bought a brass busbar that looks identical to what you showed, but opted not to use it:

All busbar s not created equal

In my new battery build, I was going to use a busbar I did not on my last build and found that this cheaper busbar had screws on that do not allow connection of the 4/0 lugs I would like to use. This shows the bottom 4/0 lug does not fit between the screws that secure the busbar to the plastic...

diysolarforum.com

One of the problems I had with the brass busbar, is not really designed to take 4/0 cables,

-I’m not a fan of 3000 watt inverters on 12 volt systems. I think 1000 watt is the limit of a 12 volt system with the exception that it is OK to go to higher wattages to do things like warm a meal in a microwave up for a couple minutes five or six times a day, but use the microwave for 20 minutes straight. The microwave I have counting inverter efficiencies pulls up to 155 amps from the batteries, or about 2000 watts at 13 volts. In part the limits are because of this:

Inverter Size vs Battery Size Tutorial. - Solar Panels - Solar Panels Forum

Discuss remote solar applications for homes, cabins, RV and boats. If you have a question on equipment for an off grid system, such as charge controllers or inverters, then post your question in this forum.

www.solarpaneltalk.com

 

[A.Justice]

This might sound like a stupid question, but is it 80° Celsius or Fahrenheit? 80° c is definitely not good, 80° f is within normal ranges.

 

[John Frum]

3000 ac watts / .85 conversion factor / 10 volts low cutoff = 352.941176471 service amps.
352.941176471 service amps / .8 fuse headroom = 441.176470588 fault amps.

Your system is constrained by the 2/0 wire and the 300 amp fuse.
Also likely the cheap brass busbars.

 

[TacomaJoe]

I'd bet on the fuse getting hot and thermal conduction heating the cables. Ramp up your load slowly and watch the fuse temperature.

 

[DJSmiley]

If you have access to a flir camera it's easy to see where the heat originates from.

If the wire is too thin, the heat should be evenly on the full wire length.
If it's a bad crimp or the fuse, that clearly pops up.

 

[eXodus]

-I’m not a fan of 3000 watt inverters on 12 volt systems.

I second that.
trying to stay under 100A when ever possible.
1200W for 12V (1500w occasional)
2400W for 24V (3000W occasional)
4800W for 48V (6000W occasional)

If you need more power on any voltage get a second inverter.

 

[corn18]

I'm good with running my MPII off 12V for now. If they had a 24V version of the MPII 12/3000 2x120, I would have gotten that. But the ease of install of the MPII 12/3000 2x120 on a 50A RV is just magical.

 

[JimJr]

Hello, 4 of my 2/0 cables gets warm to hot like 80 degrees or so, even blew the 300amp anl fuse. The 2/0 cable from the battery positive to the battery cutoff switch
doesn't even get warm, cutoff switch doesn't get hot. The 2/0 cable from the negative busbar to the inverter get pretty warm but from the negative side of the battery
to the busbar doesn't. The inverter get pretty warm like 80-90 degrees also but I'm not sure how hot they get normaly.
I have 600ah of batteries and 800 watts of solar 400w on each controller, 1 has 4 renogy 100w panels series/parallel the other has 2 200w hightec panels in series.
I haven't tried turning off the solar (not that is should matter, I think) and use the inverter and batteries to see if the cables still gets hot.
The inverter it's self has 2 grounding wires hooked to it a 10 gauge and even a 6 gauge battery cable. None of the other cables even get close to warm.
The setup is for a 50amp RV, the 3 wire output of the inverter is running to a 50amp transfer switch on the generator side and hot leg 1 is jumpered to hot leg 2.
The transfer switch doesn't seem any hotter on the generator than the shore power side. I'm not running any a/c's or big amp draws at the same time or anything but
after a few hours the cables get hot and the anl fuse smells like it's burning. Is the 300amp anl fuse too small, I ordered a few 300amp anl fuses and even
an extra 400amp fuse also. Does anyone have any ideas why only those 4 cables and fuse gets hot???
Thank You!!!

In my opinion I agree the bus bars need to be replaced , but the 2/0 wire should be ok . the lugs appear to be the thinner wall ones , they are ok for momentary high loads only. Also use washers to to spread out the clamping force more evenly . ( copper sticks to the bolt) The fuse is assemble is rated for for momentary use ( audio )

And lugs
https://www.busbar.com/resources/copper-ampacity/

Wire Size Calculator

Jimjr

 

[John Frum]

In my opinion I agree the bus bars need to be replaced , but the 2/0 wire should be ok . the lugs appear to be the thinner wall ones , they are ok for momentary high loads only. Also use washers to to spread out the clamping force more evenly . ( copper sticks to the bolt) The fuse is assemble is rated for for momentary use ( audio )

And lugs
https://www.busbar.com/resources/copper-ampacity/

Wire Size Calculator

Jimjr

How do you figure?
I showed my math earlier in the thread.

My 2/0 cables are getting hot

Hello, 4 of my 2/0 cables gets warm to hot like 80 degrees or so, even blew the 300amp anl fuse. The 2/0 cable from the battery positive to the battery cutoff switch doesn't even get warm, cutoff switch doesn't get hot. The 2/0 cable from the negative busbar to the inverter get pretty warm but...

diysolarforum.com

The least conservative ampacity table that I know of is this one.

http://assets.bluesea.com/files/resources/reference/21731.pdf

It shows that 2/0 awg pure copper wire with insulation rated for 105 Celcius in free air at an ambient temperature of 30 Celcius is rated for only 330 amps, which is less than the service current I calculated and far less than the fault current per my calculations.
Is there a problem with my math?

 

[JimJr]

How do you figure?
I showed my math earlier in the thread.

My 2/0 cables are getting hot

Hello, 4 of my 2/0 cables gets warm to hot like 80 degrees or so, even blew the 300amp anl fuse. The 2/0 cable from the battery positive to the battery cutoff switch doesn't even get warm, cutoff switch doesn't get hot. The 2/0 cable from the negative busbar to the inverter get pretty warm but...

diysolarforum.com

The least conservative ampacity table that I know of is this one.

http://assets.bluesea.com/files/resources/reference/21731.pdf

It shows that 2/0 awg pure copper wire with insulation rated for 105 Celcius in free air at an ambient temperature of 30 Celcius is rated for only 330 amps, which is less than the service current I calculated and far less than the fault current per my calculations.
Is there a problem with my math?

Not disagreeing with your numbers . But at max load on the rest of the assembly will have problems long before that 2/0 cable will . The 2awg battery wire should be connected to the buss directly for each battery . #2 is only rated for @200a . With 3 batteries set paralleled together ( not knowing the battery, 100a BMS ( typical ) ) He won't see any thing over 300a for very long before the BMS's cascade off.

 

[John Frum]

Not disagreeing with your numbers . But at max load on the rest of the assembly will have problems long before that 2/0 cable will . The 2awg battery wire should be connected to the buss directly for each battery . #2 is only rated for @200a . With 3 batteries set paralleled together ( not knowing the battery, 100a BMS ( typical ) ) He won't see any thing over 300a for very long before the BMS's cascade off.

From memory those batteries have a BMS rated for 200 amps continuous.
@Carl Boyd you should parallel your batteries using the posts method on page 19 of https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[caymaanedge]

High strand wire like Battery, Welding Cable or DLO carries a 300amp rating for 2/0 and a 405amp rating for 4/0. I have almost the same configuration and and have no issues, I'm running 4/0 everywhere.

 

[John Frum]

High strand wire like Battery, Welding Cable or DLO carries a 300amp rating for 2/0 and a 405amp rating for 4/0. I have almost the same configuration and and have no issues, I'm running 4/0 everywhere.

The strand count has no impact on the current carrying capacity of the wire.

 

[A.Justice]

I'm still waiting on clarification for the temperature units. I have a theory but don't want to sound dumb.