Did I miscalculate wire size?

[TrekkerPlanet]

Guys, so it looks like the point of resistance was the fuse itself. Where the wire and the fuse connected. It got so hot that it started to melt the shrink wrap tubing as well as the casing of the fuse itself. This happened within a 5 minute timespan.

I went head and bypassed the fuse and was drawing over 800w consistently for 20 minutes and the cable (Bus to Inverter) temperature didn't go beyond 83F degrees which I think is acceptable. I did notice that where the cable that goes from the Battery to the On/Off Switch was at 89/92F. Wondering of I missed something there.

Every other connection was at or near room temperature.

 

[740GLE]

That's correct.

Is the fuse base also in direct contact with the buss bar with the washers and nut on top?

Correct, the stud is isolated from the bus bar so all current must travel through the fuse.

 

[740GLE]

Guys, so it looks like the point of resistance was the fuse itself. Where the wire and the fuse connected. It got so hot that it started to melt the shrink wrap tubing as well as the casing of the fuse itself. This happened within a 5 minute timespan.

I went head and bypassed the fuse and was drawing over 800w consistently for 20 minutes and the cable (Bus to Inverter) temperature didn't go beyond 83F degrees which I think is acceptable. I did notice that where the cable that goes from the Battery to the On/Off Switch was at 89/92F. Wondering of I missed something there.

Every other connection was at or near room temperature.

I take it Amazon “letter salad” brand fuse and fuse holder?

Glad you sorted it out.

 

[soylentgreen]

I like the idea of a bogus MRBF.

However, I also notice some red melted insulation on top of the fuse pad - could you have accidentally trapped some part of the red wire insulation between the fuse and connection causing a high-resistance connection?

 

[MisterSandals]

I like the idea of a bogus MRBF.

However, I also notice some red melted insulation on top of the fuse pad - could you have accidentally trapped some part of the red wire insulation between the fuse and connection causing a high-resistance connection?


View attachment 292360

Yes, you gotta watch the shrink wrap too for this.

 

[soylentgreen]

In fact, doing more zoom + enhance, I think I see clear evidence of a pretty sizable patty melt going on...




Looks like you caught some red insulation under the right edge of that fuse?

 

[TrekkerPlanet]

That's correct.

Is the fuse base also in direct contact with the buss bar with the washers and nut on top?

What brand MRBF? Cheap ones are cheap you know.

Can you get a close up picture of the connections?

You could try and remove the MRBF from the bus bar and go direct lug and see there is heat generated.

I bypassed the MRBF and the wire didn't go beyond 82f degrees. The point of resistance was the fuse itself.

 

[Koyaanisqatsi]

Also this:



Looks like battery terminal corrosion resistant spray. Gotta clean up that fuse and the stud plate.

 

[740GLE]

In fact, doing more zoom + enhance, I think I see clear evidence of a pretty sizable patty melt going on...

View attachment 292365


Looks like you caught some red insulation under the right edge of that fuse?

Except the lugs had black heat shrink.

This may have been the red mrbf insulation cap that also got warm when the heat of the bad fuse couldn’t escape.

I’d be curious about the other fuses.