wires burned up with 4 100 watt panels

[uptickguru]

Originally Posted by Sailing Ohm

Forget the fuses and get a fast acting breaker designed for solar and rated for your system.
Your panels are rated at ~30 amp output at 12vdc. I’d get a 40 or 50 amp breaker (you always want more room on the breaker/fuse than the absolute minimal required)
Upsize your wire by one or two gauges. (Why play it so close?)

If you have mppt controller (if you don’t have one you should they are worth it) running panels in series will allow smaller gauge wire (if cost or hole size is an issue) and you’ll actually get more power long term.

If none of this makes sense hire someone.

I agree with this. I run 600W in two string of 300W per string wired in series for a Max Output of 72V at 15A into a 100/20 Victron MPPT Smart Solar. Each string has its own controller as I have one on the port and the starboard side due to shading from sails. Crazy thing is I have never come close to 600W or even 300W on each string dues to shading, bird poop, etc . I have 10 Gauge cable connecting all and have thermal breakers of 25 amps between the panels and controllers and 25 Amps between the controller and batteries. I am an electrical engineer and I put blue sea thermal breakers on all connections. I have seen a controller connect the batteries directly back to the panels when it failed popping the isolation diodes on the panels. I not longer buy chinese converters off ebay. Laughs. That one was scary.

My suggestion is to disconnect the panels. after covering them with a towel and see if you have residual voltage on the leads where the panels connect. Also, get a cheap meter with a current clamp and clamp only one of the panel cables going to controller and then plug each panel back in one at a time. This will give you an idea if you are pushing too much current. Try each panel individually and then both in parallel.

Also I like to push the highest amount of voltage I can to the controller as it will convert to the proper voltage and current for the set battery type. Hence my 300W in series. This is usually around 14.4 volts for bulk on my lead acid bank and controller will limit the current automatically if you have the correct battery type set. The more voltage the less current and you can use a smaller size wire and breakers etc. I always make my system identical and redundant as you can bet one will fail when you need it. Especially on a boat usually in a place where you can't get spares. I carry a spare system of the exact thing above that I deploy when we get somewhere we are staying a while and want to break out the ice machine and blender for some adult beverages. These also act as my spares.

I always believe in smaller identical system components over one large controller as everything is simpler, safer, and best of all, less expensive to maintain and repair. Leaves more funds to keep the blender full.

Best of luck to you!

[SSgtPitt]

Lot of really good information here when sorted through.
I was having nearly the same problem. I have 4 - 100amp panels run to a Epever Tracer 40amp MPPT controller. It’s worked great for 4 years.
Then blew a 60amp block fuse from the controller to the batteries twice.
After a couple days checking everything I found the controller must have shorted because the positive cable leaving the controller was now internally grounded somewhere in the controller and the display on tje controller no longer works.
The only thing that has changed was we moved the boat from the storage yard to the work yard 3 weeks ago and plugged into land power. Maybe during the move something happened.
I also did not unhook the controller before connecting and disconnecting the panels, so maybe I caused it. I will unhook next time.
I have a new controller arriving today.

[Slacktime]

This cannot be the wire size. If the 10 awg wire was overloaded it would eventually melt the insulation along the entire length. Check connections for corrosion after repair check the resistance of the connection. Make it good and solid use conductive grease if necessary.

[Nicholson58]

Originally Posted by s/v Thea

400 watts / 12.5 volts = 32 amps

Assumes series connection.

This sounds more like a fault permitting the batteries to discharge through the solar circuit.

[Talbot]

I had a similar incident to the OP.

My system 3 x 185 watt =555 watts Through an Outback Flex 80 controller and a 50 amp fuse.

One very hot day mid summer in the middle of the Bay of Biscay, my solar stopped charging. When I investigated - the fuse should have been sufficient, but the expert believed that operating at max capacity for a while, it had heated up (so less efficient, and this compounded the problem until the fuse holder had melted completely and disconnected the circuit.

I replaced the 50 amp fuse with a 75 amp breaker - not been a problem since.

[eMarineSystems]

Sounds like the fuse and fuse holder is the problem. Inexpensive barrel fuses and holders have such high connection resistance that the heat will build up and cause things to melt. Recommend using a Maxi fuse type fuse and holder. The 10gauge wire is a little bit light in size and would recommend going to and 8gauge wire as was mentioned in one of the other posts, this is to be on the safe side.

How are the parallel panels connected? Buss bar, terminal block? If you are using an MC4 splitter arrangement, keep in mind that these connectors are only good for 25 A. We typically recommend maximum of 22 A to be on the safe side. These these will heat up and melt as well when you push too much current through them. You might want to check them to be on the safe side.

[skenn_ie]

400W at 18V MPPT is equivalent to 22A. £0A would be a good protection fuse. Wire gauge is selected for voltage drop rather than current capability in sub 50V systems. The lower the working voltage, the more sensitive the components get to voltage drop.

[KPRick]

So that I can look up the specs and provide some guidance:
What charge controller are you using?

What is the open circuit voltage of the panel? (Voc) or better yet what panels are you using?

[Aethelwulffe]

This one has my +1.
4 100W panels, assuming that the voltage/wattage ratio does not have some weird spot that allows the current to achieve 200% of assumed load, is never gonna get close to putting a hunk of *verified quality* 10ga cable of either fancy soft boat cable or a hunk of romex into position of smoking out the cabin.
HOWEVER:
Lightning happens. Electrolite intrusion (salt water) happens. Galvanic corrosion happens. If your insulation has a bunch of blue vertigis gunk in it, yes, the whole wire may think it is a heating element. Stray currents and shorts happen. Regulator failures happen. Fancy inverter/charger/iso transformer failures happen. One goofy microcontroller and you may never figure out what it did.


Personally, I am a fan of high DC voltages with very short runs, but short answer is that hacking into a wire and adding a cheesy fuse holder introduces more possible dangers than it fixes. Buss bars with ring terminals and a good simple bridge of automotive style spade fuses (please let pole fuses die forever!) in a single unit box, and if you exceed the rating of the fuses, they die silently. Any other behavior and I would use the operative assumption you are merely dealing with crap material, despite what the package said and how much they made you pay.


In whatever situation, I hope you find something you can confidently say "yeah, this is what happened". It would not be fun to have to clench your jaw with worry every day around noon.

[Mudfoot57]

Just a thought if there were poor crimps, broken strands or a high resistance connection caused by surface corrosion it is possible at high currents for the heating effect to melt the adjacent cable insulation or mounting around the fuse holder depending what it's made of.

The heating effect is I X I x R hence at or around 20A that's 400W for 1 ohm resistance, and still 100W with 20A at 0.25 Ohms.

There is an element of diversity assumed in gauging most battery or supply cables relating to the intended loads but the fusing should always be rated to protect the cables rated capacity. Not to the total load current if everything on the circuit I switched on.

If you are thinking or have Stainless Steel Crimps with Aluminium stranded cables on main high current cables, it's my limited experience with some at work on a 100A test that the crimped junctions get very hot.

David Hadaway

Reading, England