Help! Melting negative wire

So I had my Chinese diesel heater running for about 5 hours today with no issues. The heater is wired straight to the battery as recommended. I have a fuse panel that I had just wired my 6 led ceiling puck lights to. After about 5 mins my lights went dim, the heater lost power and I noticed smoke coming from the wire that goes from the negative terminal on battery to the negative on the fuse block. The wire melted and almost caused a electrical fire. The wire seemed to be pretty loose on the negative terminal on the fuse block and I was able to rip the wire out before any fire happened. What could be the issue here? Battert voltage dropped too low? I have 2 100watt solar panels wired to a renogy 30amp wanderer charger. The batt light was red and so was the PV light was red as well.

Loose or corroded connection causing excessive resistance leading to excess heat. You said the connection was pretty loose, which leads me to believe that there was way too much resistance (causing heat). Also, what gauge wire are you using? If the wire is too small it could heat up like that. Is there a fuse on the positive wire between the battery and the fuse block? If so, what’s it rated at? What’s the wire gauge?

All the terminal connections that I use are both tightly crimped and then soldered. The crimp makes the physical connection, and solder keeps moisture out and reinforces the physical connection. Terminal lugs should be free of corrosion or tarnish in the case of silver. If you live in a wet climate, use dialetric grease to seal the terminal screw connections. You want lots of clean metal surface area on all connections, screwed tight. Squeeze the dielectric grease into the connection AFTER screwing it tight - clean metal to clean metal, nice and tight, then the grease.

Be sure to use proper gauge wire for the amp load, and be sure it’s stranded wire. Stranded wire is less likely to break when subjected to vibration in a vehicle. Solid wire is only for houses/buildings. I usually go bigger than what’s called for.

Wire gauge chart. For your 30-amp system use 10 gauge minimum, 8 gauge is better. That’s assuming that the wire length is less than 10 ft.

Also make sure that every circuit has a fuse appropriate for what’s on it. How many amps do your “Puck lights” draw? All together, how many amps does your whole system use?

I have a 12 Ga wire on there. I will go to a 8 or 10 today. And the lights it said 3 watts online. And thank you very much for the response!

Okay, the lights draw almost nothing, probably LEDs. But since that’s all you changed be sure the wiring for them isn’t chafing/grounding on something. After installing the new wiring, give them a good tug to be sure everything is tight and secure, and that each circuit has an appropriate size fuse. The wiring between the battery and fuse block should also have a fuse close to the battery. Fuses always go closest to where the energy comes from. Good luck.

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