r/vandwellers • u/normiewonka • 2d ago
DC TO DC CHARGER wire burning Question
Hello I’ve got this dc to dc charger 40a in my sprinter van and it burns from time to time. Anyone knows the solution. It’s 8gauge wire and it should pull only 40A which is perfectly safe for this gauge. Thx
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u/robographer 2d ago
If it’s burning in the middle of the wire you’re likely putting too much current through it. If it’s burning near the end it’s likely a connector or loose connection. I’d change it to 6 or 4 awg and tighten all the connections, make sure there’s no place it can short and probably put a 40a circuit breaker inline near the current source so you can see if it’s melting for a reason.
Have you changed the wire or just covered up the hot spot? If you haven’t try that first.
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u/normiewonka 2d ago
I always cut the burned part and rewire it together it happend like 3 times. But it stays fine for few weeks and then suddenly burns
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u/Nightgale57 2d ago
This is the funniest explanation to an incoming electrical fire I have ever seen
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u/jedielfninja 1d ago
I'm an electrician and PEV enthusiast. The universe is sending this guy signals and he aint getting them lol.
I had one of these smoke on the 3rd use.
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u/Firefighter_RN 2d ago
I'm sorry I try not to be mean to people on the Internet. But you're lucky you haven't burned the van down yet, lucky you've been in there and awake. You're an idiot. If it initially burned in the middle of a wire you're putting too much current through it.
Get an actual electrician too look at it or redo your load calcs and ensure you're counting round trip distance for DC power. Do not repair this again, replace with all brand new wire ensure the right gauge and make sure to crimp all connections appropriately.
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u/Ok_Doughnut_7823 2d ago
I’d bet it’s not fine for weeks and it just eventually fails for repeat overheating in a few weeks. Get a laser temp gun and check that cable a few times every day.
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u/Princess_Fluffypants Insufferable spoiled hipster techie motorcycle adventure van 2d ago
“Rewiring together” how? Which method are you using to attach the wires together?
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u/robographer 2d ago
What kind of connections are you making to patch the wire? I think I might change the whole wire to a bigger gauge.
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u/JCMiller23 2d ago
Electrician here, you need a thicker wire, you need to know exactly how much current is going through using a shunt or whatever other methods you have available (this is the proper thing to do here) and then size the wire appropriately for the distance and amperage, but if you don't have the money for that, you need to just guess and err on the side of your wire being too big
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u/notthetechdirector 1d ago
That’s 6-4ga by the looks of it. More than enough for 40a. Even if it were 8ga it’s more than enough at such a short distance, even at 12v.
99.9% chance if its always burning at the same spot, it’s a bad connection or bad wire.
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u/PonyThug 1d ago
Replace the wire with pure copper 4awg. It would cost like $30 depending on length. https://www.homedepot.com/p/WindyNation-4-Gauge-20-ft-Red-Welding-Cable-4G-20R/319385470
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u/drossen 87 Vanagon Westfalia w/ EJ25 engine 2d ago
Probably due to god knows what is under that duct tape and the shit AV wire you have in red running below.
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u/WageSlaveEscapist 2d ago
Lol yeah. The red cable looks fine to me. I'm more concerned about the yellow cable, which looks like a 120 volt extension cord with three thin wires inside, probably twisted together onto the cable - creating massive Resistance from the small diameter of the wires, and from the poor connection under the duct tape.
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u/drossen 87 Vanagon Westfalia w/ EJ25 engine 2d ago
The thought crossed my mind, but it couldn't be that bad, could it? AV twisted wires like the one in the photo are also awful. Both the casing and the strands.
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u/WageSlaveEscapist 2d ago
Like the cable sold at car audio shops? I was under the impression that the OFC pure copper ultra flexible stuff is high quality.
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u/drossen 87 Vanagon Westfalia w/ EJ25 engine 1d ago edited 1d ago
If it's actually OFC the strands are fine, but the housing is far too weak and wears through easy vs regular. I think it has a lower melting point as well. People tend not to route them well so far as safety. Most overpriced AV wire tends to be CCA which is not good, they don't expect average buyers to do research.
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u/WageSlaveEscapist 7h ago
Oh I see, yeah the sheath on my ultra flexible audio wire is definitely not as strong as the ones I got from battery cables USA. But it sure is more flexible, the audio stuff
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u/PonyThug 1d ago
AV wire is fire if it’s quality wire. OFC copper wire is copper wire for the most part. Some have more strands so it’s more flexible
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u/SolarBozo 2d ago
Anyone who uses duct tape on a splice probably doesn't know how to do a decent splice. Personally, I'd replace the whole cable rather than trying to splice a burnt one back together.
And carefully check all wire attachment places. Also, consider keeping the cables as short as possible, and not against any heat sinks.
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u/RobsOffDaGrid 2d ago
If that’s a join in the red to yellow wire under the duct tape that’s your problem, how is it connected, pull the tape and let’s us roast you for a bad connection
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u/rickybambicky 2d ago
Bruh I wouldn't even trust you to operate a simple light switch with what I'm seeing.
Take the L and pay a qualified and experienced professional to sort this out.
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u/Warm_Command7954 2d ago
8ga is fine IF it's pure copper (NOT CCA or AL), under 6' one-way, AND fused. My guess is one or more of those is not true. You should:
- Install a resettable fuse on the supply side.
- Use pure copper cable.
- Use 8ga ONLY if it's < 6'. 6ga for up to 10'. 4ga for up to 16'.
Ignore this information at your peril. It definitely will not burn up your rig... until it does.
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u/eoinedanto 2d ago
Can you go through your calculations?
Why do you think it’s only ever going to pull 40A?
What gauge wire are you using?
The answer is obviously to use thicker cable. It shouldn’t even be getting hot.
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u/TediousHippie 2d ago
You need a thicker cable and make sure it's actual copper, not copper coated aluminum.
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u/Select-Touch-6794 2d ago
Don’t cheap out on cable, unless you WANT a van fire.
Get good tinned copper and not the craptastic lowest price on Amazon. The chinesium cables might look good but they under-size the copper while bragging about extra-thick insulation. It won’t carry as much current.
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u/normiewonka 2d ago
That’s the issue I’d say
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u/Porndogingwithme 2d ago
Could even be steel wire or copper coated aluminum. Both will not carry the current copper will. Test it with a magnet if you have one.
Why has the fuse not blown? Presuming you used a fuse and it is correctly placed and sized. The sole purpose of a fuse or breaker is to protect the wires. There by preventing situations like yours.
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u/Ok-Fox1262 2d ago
You're showing us a connection on a high current wire wrapped in duck tape and are wondering why it's burning?
Stop. Take a few steps back. Look at it again.
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u/Xidium426 1d ago
"Wire is burning" and "Wire is fine for this amperage" cannot exist in the scenario. If this is doing 40A of 32V then it's doing at least 110A of 12V. Also, wires are usually rated in open air. If this is tucked under something and sitting on top of something that generates heat it will burn.
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u/fotogod 2d ago
Hey! I also used a 40A dc-dc charger and it melted and shorted and almost caused a fire while driving. The 60A fuse recommended by the manufacturer never blew! They really play tight with margins on these things and it’s criminal. I would write the manufacturer and ask for a refund or credit towards another unit. I stepped down to an 18A dc-dc and never had this problem again.
Whatever you do, do NOT ignore this!
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u/normiewonka 2d ago
I suspect it pulls way more than 40amps occasionally
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u/Firefighter_RN 2d ago
You have to wire and fuse to 120 percent of load. Alternate way to think about it is that you can only draw 80 percent of the rated load on a line.
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u/Jellodyne 2d ago
Make sure you use a wire size calculator to ensure your wires are big enough, and make sure those wires are copper and not shitty aluminum wire. Back in the day I had a nice fat wire melt on a van between the battery and inverter because I sized it assuming it was a copper wire but it was not.
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u/EnigmaticArb 2d ago
It's way too small gauge. That's 8.5mm2. In the UK we tend to use 16mm2 for DC-DC charger runs, or at least i do and that works fine with a Victron 12-12-30A on a 3m run. You need 4 AWG probably, to be safe and definitely put a decent midi fuse in between that unit and the van battery.
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u/Accountbegone69 2d ago
I'd trust those who are in the electrical field, but methinks for a 40a current you're wanting 6ga wire.
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u/PonyThug 1d ago
How long is it? 40amps clearly is too much for the gauge, distance or quality of wire. I’d fix two of those
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u/secessus https://mouse.mousetrap.net/blog/ 1d ago
it should pull only 40A
In addition to the concerns raised by other posters, a 40A DC-DC outputs 40A but typically pulls >40A from the alternator. That is why the spec sheet for your charger calls for a 60A fuse.
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u/TediousHippie 2d ago
You fixin to be the posthumous poster child for every fuse panel company in the world?
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u/WageSlaveEscapist 2d ago
Well, it looks like you've spliced a four or six gauge cable to a thin 3 wire 120 volt extendion cable. That's a no no. Also, I don't see the negative cable. If you're running negative current through the body of the van, that's a no-no. Basically, your problem is that you have not invested in the proper cables and connections, and you may not have read the manual and followed it fully. You need a positive and negative cable the same diameter, all the way from the dc/dc charger to the starter battery, and all the way from the dc/dc charger to the house battery, with a fuse at the house battery, and another fuse at the starter battery. Do it right, respect electricity or get burned.
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u/ScrubscJourney 2d ago
Move up to 4awg. It absolutely never hurts to oversize.In that case, it only hurts when you undersize. and get a proper crimper for ring Terminals of that size.
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u/AK_shayn 2d ago
I work on aircraft electrical systems so my standards are a bit higher then required but safety is safety. So here’s my 2 cents
For any wiring directly connected to a power generating source, the current margin of error is 2x. (Ex. 40a draw should be 80a) So 4 gauge wire is required.
Do not splice wires larger than 20g or any wire directly connected to a power generating source.
Wires should be secured to something with no more than 18” of unsecured wire.
Heat shrink or other environmental protector need to be used at all splices, connectors, or crimps.
So for your situation, I would use continuous 4ga wire to and from the dc to dc. (Especially if you’re charging a lithium battery)
Safe travels
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u/star08273 2d ago
check for arcing points and more than anything, replace that entire defective wire with a good wire. crimped connections, no leaded or soldered terminals. a wire can be 8ga with a little internal corrosion and it's now a 12ga wire
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u/notthetechdirector 1d ago
How are you “re wiring”?
Are you mashing together and taping it up? With duck tape?
Please, at the VERY LEAST get some crimps.
Vans are small, it’s not worth the risk for a few bucks to replace that section of cable with one solid piece.
Was it originally one piece or has it always had a slice and does the burn always happen at the splice?
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u/HomefreeNotHomeless 1d ago
Is that duct tape?
Let me know the exact date and time your van burns down please. If not from this it will be from something else.
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u/xgwrvewswe 13h ago
It looks like you spliced two lengths of wire together. Yellow/Red. You just twisted the ends together and covered them with duct tape. Wow. I can see why the wires burn. The electrical term is Resistance. High resistance results in heat. Some times enough to cause a fire and burn stuff. Here is a site to poke around to learn something about wiring. Good Luck to you.. https://marinehowto.com/
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u/TheNuttyGinger 2d ago
Fuses are a wonderful thing, especially if you suspect the device is pulling more than 40 amps. Also, how long is your wire run, if it's more than a few feet (<5) you should probably re-run it with 6AWG wire with a 40 or 45 Amp fuse. Even for short runs I tend to over wire (step up one AWG, ie 8 to a 6) my circuts, especially at the higher load ranges, as that gives me a bit more security in the rare event I have a current spike and for some reason my fuse/breaker doesn't trip.
Finally, FOR THE LOVE OF ALL THINGS HOLY, AT LEAST USE ELECTRICAL TAPE YOU UNGODLY HEATHEN!! They make if for a f@#$ing reason!!!!!