Renogy DC-DC charger - heat at fuse

[MountainBiker]

Hi folk. I have replaced the inline breakers (tried a few and none worked...they tripped OR the charger would blink on and off) that I originally had between the disconnect that goes to my Van battery (180a alternator) and the DC-DC renogy charger with a fuse as in the picture below. In the diagram you can see the relevant parts. I am getting heat at the connection of the fuse and wire that goes to and connects with the DC-DC charger. The fuse seems to "work" "but its warm to the touch but not really hot. I am thinking of replacing the wire from in the segment from the existing 6awg to 2awg.

I am looking for any advice about this. I will test it but worry i will only transfer the heat somewhere else...like maybe to the charger itself. Thoughts?

 

[Checkthisout]

Hi folk. I have replaced the inline breakers (tried a few and none worked...they tripped OR the charger would blink on and off) that I originally had between the disconnect that goes to my Van battery (180a alternator) and the DC-DC renogy charger with a fuse as in the picture below. In the diagram you can see the relevant parts. I am getting heat at the connection of the fuse and wire that goes to and connects with the DC-DC charger. The fuse seems to "work" "but its warm to the touch but not really hot. I am thinking of replacing the wire from in the segment from the existing 6awg to 2awg.

I am looking for any advice about this. I will test it but worry i will only transfer the heat somewhere else...like maybe to the charger itself. Thoughts?

I had that exact fuse holder and returned it because it got hot.

I verified it wasn't a bad crimp by bolting both cables to the same post.

 

[MountainBiker]

Thanks! Did you try to increase the size of the fuse? ie...i could put in a 70amp fuse because...maybe its a wee bit too small?

 

[grizzzman]

Thanks! Did you try to increase the size of the fuse? ie...i could put in a 70amp fuse because...maybe its a wee bit too small?

What is the Amps rating for the DC to DC charger? never mind the pic shows it to be a 40 amp unit. When testing my Renogy 40 amp DC to DC charger at 14.7 output the input amps was 50 amps. Without voltage drop info it is hard to say. The purpose of the fuse is to protect the wire in case of a short. If you changed the wire to 2 AWG you could go to a much larger fuse. This would reduce the voltage drop across the fuse.

 

[Checkthisout]

What is the Amps rating for the DC to DC charger? never mind the pic shows it to be a 40 amp unit. When testing my Renogy 40 amp DC to DC charger at 14.7 output the input amps was 50 amps. Without voltage drop info it is hard to say. The purpose of the fuse is to protect the wire in case of a short. If you changed the wire to 2 AWG you could go to a much larger fuse. This would reduce the voltage drop across the fuse.

In my case the fuse mounting post is what got hot, not the fuse itself.

Same fuse in a different holder (Fastronix) was fine.

 

[Checkthisout]

Thanks! Did you try to increase the size of the fuse? ie...i could put in a 70amp fuse because...maybe its a wee bit too small?

The fuse itself didn't get hot, just the mounting post and cable end.

Just one of the many frustrations on my solar learning curve.

Changing to a different fuse holder solved the issue.

 

[MountainBiker]

The fuse itself didn't get hot, just the mounting post and cable end.

Just one of the many frustrations on my solar learning curve.

Changing to a different fuse holder solved the issue.

OK. Its the same for me. the mounting post is the warmest bit followed by the lug/wire that runs out to the DC-DC charger.

 

[MountainBiker]

What is the Amps rating for the DC to DC charger? never mind the pic shows it to be a 40 amp unit. When testing my Renogy 40 amp DC to DC charger at 14.7 output the input amps was 50 amps. Without voltage drop info it is hard to say. The purpose of the fuse is to protect the wire in case of a short. If you changed the wire to 2 AWG you could go to a much larger fuse. This would reduce the voltage drop across the fuse.

Its a Renogy 40a DC-DC charger. The Amp Rating is 40a. It also specifies the current limit at 20a. How did you test your DC-DC charger at 14.7a output (edit>never mind...you tested it at 14.7v I assume<edit)... Mine basically charges at 37amps. The dipswitches on it are for specifying the type of battery and the voltage behaviour over the charge.

 

[MountainBiker]

What is the Amps rating for the DC to DC charger? never mind the pic shows it to be a 40 amp unit. When testing my Renogy 40 amp DC to DC charger at 14.7 output the input amps was 50 amps. Without voltage drop info it is hard to say. The purpose of the fuse is to protect the wire in case of a short. If you changed the wire to 2 AWG you could go to a much larger fuse. This would reduce the voltage drop across the fuse.

Just thinking more about what you are saying....if there's a voltage drop across the fuse...other things being equal, there will be an amperage rise leading to more heat. If I increase the wire size, it should reduce the voltage drop and the amperage...thus reducing heat. Sound right? I think its very possible that I need a new fuse holder as suggested by Checkthisout but I have some pieces 2awg wire so Ill try this out and see if it reduces the heat.

 

[Checkthisout]

Just thinking more about what you are saying....if there's a voltage drop across the fuse...other things being equal, there will be an amperage rise leading to more heat. If I increase the wire size, it should reduce the voltage drop and the amperage...thus reducing heat. Sound right?

Bypass the fuse by attaching both cables to same post and re-test just to make sure you don't have a bad crimp.

The other thing that can be an issue is washer placement.

Make sure that's all correct.

 

[MountainBiker]

Bypass the fuse by attaching both cables to same post and re-test just to make sure you don't have a bad crimp.

The other thing that can be an issue is washer placement.

Make sure that's all correct.

Will do. I should add that after 20 minutes of running, the fuse isn't "blowing" its just as you said...the post is hot and the wire is warm at the lug end that attaches to the post.

 

[MountainBiker]

Tried a larger size wire and still getting heat at the post. The hot post end of the fuse is hot as well. Ill try a different fuse and if no luck, ill send it back and try a different fuse holder.

 

[MattiFin]

Just to make sure: there was no washer between the fuse and the cable lug?

When the lugs are bolted directly to the fuse the fuse ”holder” has very little to do with heating and differences between brands and models are mostly irrelevant.
Sure, some fuse holders migh have more holes to allow the fuse to cool a little bit better.

And some heating on fuse is perfectly normal on fuses. For fuses with ceramic body the fuses can heat up to burning hot(60…100C) under nominal max current. Plastic fuses should stay cooler, maybe 20-30C temp rise above ambient.

 

[Checkthisout]

Tried a larger size wire and still getting heat at the post. The hot post end of the fuse is hot as well. Ill try a different fuse and if no luck, ill send it back and try a different fuse holder.

So lastly, make sure the nut is tight. People have a tendency to under-torque things.

If you apply hefty side pressure to the cable and it will rotate on the stud then it's not tight enough.

The other thing, if the stud is say 1/4 and your cable end has a 3/8 hole, that will also cause high resistance.

I controlled for all this and ascertained that in my case, the studs and fuse were made of material not suitable for electrical connections. That happens with stuff sometimes.

 

[MountainBiker]

Just to make sure: there was no washer between the fuse and the cable lug?

When the lugs are bolted directly to the fuse the fuse ”holder” has very little to do with heating and differences between brands and models are mostly irrelevant.
Sure, some fuse holders migh have more holes to allow the fuse to cool a little bit better.

And some heating on fuse is perfectly normal on fuses. For fuses with ceramic body the fuses can heat up to burning hot(60…100C) under nominal max current. Plastic fuses should stay cooler, maybe 20-30C temp rise above ambient.

Thx. Yes, from bottom up its washer, fuse, lug, washer, lock washer the nut. Its not burning hot...just.. hot. I have a few more fuses coming tomorrow so ill try one of those a d see if it makes any difference!

 

[MountainBiker]

So lastly, make sure the nut is tight. People have a tendency to under-torque things.

If you apply hefty side pressure to the cable and it will rotate on the stud then it's not tight enough.

The other thing, if the stud is say 1/4 and your cable end has a 3/8 hole, that will also cause high resistance.

I controlled for all this and ascertained that in my case, the studs and fuse were made of material not suitable for electrical connections. That happens with stuff sometimes.

I haven't focused on
matching lug size to post diameter. Ill try that too. To me the odd thing is that its just that one fuse holder post that's warm....nothing else. I've tried a few diff cables of different sizes on that post and still hotish.

 

[Checkthisout]

I haven't focused on
matching lug size to post diameter. Ill try that too. To me the odd thing is that its just that one fuse holder post that's warm....nothing else. I've tried a few diff cables of different sizes on that post and still hotish.

Flip the fuse holder 180° and re-test to see if the other post gets hot.

Or just wait and see if a new holder helps.

Which one did you order to replace it and what brand is that? RENOGY? WINDYNATION?

 

[MountainBiker]

Flip the fuse holder 180° and re-test to see if the other post gets hot.

Or just wait and see if a new holder helps.

Which one did you order to replace it and what brand is that? RENOGY? WINDYNATION?

I have some different fuses coming tomorrow so I am going to try that first but swapping the posts is a great idea too. If these two things fail, ill get a new holder. Its a Renogy. I dont know why i bought there brand; i guess because its a renogy dc-dc charger that its connected to lol. Most of the stuff I have is renogy. One throat to choak?

 

[Checkthisout]

I have some different fuses coming tomorrow so I am going to try that first but swapping the posts is a great idea too. If these two things fail, ill get a new holder. Its a Renogy. I dont know why i bought there brand; i guess because its a renogy dc-dc charger that its connected to lol. Most of the stuff I have is renogy. One throat to choak?

Mine was also a Renogy. You can see my 1 star review of your exact fuse holder on Amazon due to the exact same problem you're having.


Edit:

My bad. Mine was a windynation but they are the exact same fuse holder.

 

[Checkthisout]

Thx. Yes, from bottom up its washer, fuse, lug, washer, lock washer the nut. Its not burning hot...just.. hot. I have a few more fuses coming tomorrow so ill try one of those a d see if it makes any difference!

FYI, you're out of order.