wires burned up with 4 100 watt panels

[CharlieJ]

Agree, but...there is always a but...I prefer the breaker between the panel and the controller, near the controller, as well as an output breaker between the controller and the battery. I then follow the ABYC 7" rule at the battery. With this scheme:
1. I can easily isolate the panels from the controller.
2. I can easily isolate the bank from the controller and have an easy method for bring DC back to the controller from the bank after controller programming.
3. The fuse at the bank keeps surveyors content that the installation is in compliance with ABYC Standards, voluntary as they are.

And since UL 489 DIN CB are relatively cheap ($30 for a DPCB; 125VDC/63A) it seems reasonable.

[Cadence]

I get a kick out of the positioning of the fuse in the length of wire. It is amperage that blows it and it doesn't really care where in the wire it is located.
Maybe if you expect the wire to be shorted to ground.

[smac999]

Originally Posted by Cadence

I get a kick out of the positioning of the fuse in the length of wire. It is amperage that blows it and it doesn't really care where in the wire it is located.

ok do this test. hook up a 20' long wire to you battery. put a fuse 18' away from the battery. now 10' from the battery strip away the cable sheath and thouch the inner wires to your engine block.

let me know if the fuse blows and what happens.

[Cadence]

Originally Posted by smac999

ok do this test. hook up a 20' long wire to you battery. put a fuse 18' away from the battery. now 10' from the battery strip away the cable sheath and thouch the inner wires to your engine block.

let me know if the fuse blows and what happens.

I love partial quotes. And if that's the case the dressing of wiring runs would be suspect.

[noelex 77]

Originally Posted by smac999

it's a self limited power source. the controller does not need a fuse on the controller side. nor do alternators, battery chargers. and solar panels. they are self limiting sources of power. the power will never exceed the amp rating of the cable.

The maximum current that can be generated by the solar panels is self limited, but with multiple panels the combined limit may be higher than the rating.

Where this applies, fusing on the solar panel side (in adittition to a fuse between the controller and the batteries) is needed to avoid the problem of a fault condition melting the internal wires and starting a fire.

[Gary Mc]

Originally Posted by Cadence

I get a kick out of the positioning of the fuse in the length of wire. It is amperage that blows it and it doesn't really care where in the wire it is located.
Maybe if you expect the wire to be shorted to ground.

The over current device is sized and installed to protect the conductor, not the load, so to do that it needs to be installed next to the source.


I agree with what has been suggested here, that the high resistant connections at the fuse block, is the likely source of the smoke!

[hzcruiser]

Originally Posted by Gary Mc

The over current device is sized and installed to protect the conductor, not the load, so to do that it needs to be installed next to the source.

[..]

That's correct. The person "getting a kick out of it" did not grasp the basic reasoning behind the concept. Time for him/her to kick himself ?

[Emouchet]

What is the brand of the fuse and fuse holder ? Is it a cheap made in china fuse box ?

[mcon12000]

Ok there is so much bad information on this thread that I suggest not reading it.

I’m an ABYC certified marine electrician and you need to either hire a pro immediately or replace your system with a professionally designed one. You need an audit of what you have by someone with experience and training it will be the best money you’ve ever spent.

The amount of bad advice on this thread if horrifying.

[djdeakyne]

Put your panels in series, or at least 2S2P. That will 1/2 or 1/4 your current and your 10ga wire will be fine.

[geekoman]

The amperage capacity of 10 awg is 30 amps - doing a quick Google and seeing several concurring sources. If you can find your wire's manufacture and wire type, you can find the actual value. All my comments below are predicated that your 10AWG wire can handle the 30 amps.

Your solar panels are 100W each and will output at best 8 Amps each. "At best" because output voltage of the panels will be greater than 12 V, so current will be 8 Amps or less from each panel. In reality the panels will output more than 12 Volts, and current goes down as voltage goes up with constant watt output.

So the 10AWG wire coming from each panel is more than adequate to handle the panel's output current.

The cables from the panels feed into a solar charge controller. Right?

The output of the solar charge controller is 12 to 14 V, depending on the charge controller, the batteries being charged and their charge state. Worse case for amperage calculation at 12 Volts. So your charge controller will output 400W / 12 volts or 33.3 Amps. This will occur when your solar panels are outputting at 400W, which will not be often. But, can happen.

The maximum current output of the solar controller dictates that the wire going from your solar controller to your batteries should be 8 AWG or 6 AWG, carrying 40 and 55 Amps respectively. 10 AWG will not handle the expected loads when your getting 400W of solar power. You got away with this (sort of) because you do not often get 400W and the output voltage is above 12 V, probably 13, so current output is 300W / 13 V = 23 Amps.

Using 6AWG with a 50Amp fuse is how I would install the after controller to my batteries. The 6 AWG wire goes for both positive and negative branches. Fuse goes on the positive side, nearest the charge controller.

A reason your fuse block melted might be because the contacts were in bad shape. Bad contacts generate heat at the connection (even if the current is only 10 Amp and fuse does not blow) the block will heat up. Ensure the connections are good (i.e. clean and tight) and ensure that the block is designed for that size fuse.

While you are sorting all this out, you may be able to limit the output of the solar charger to 25 Amps and install a 30 amp fuse to the output cable. My Victron controller can limit current output, you'll need to see if your controller has this capability. Else, there is a chance the wires from the controller to the battery will melt and ruin your day. This will limit your solar generation, but it will help keep your boat afloat.

Another alternative for short term fix, after cleaning up all the connections and replacing the fuse with a 25 Amp fuse, is simply disconnect one solar panel. With only 300 W maximum output, your are in the capacity range of the 10 AWG wire after the controller. 300W / 12 V = 25 Amps, and your 10 AWG wire from the controller should handle this.

Again, look up the amperage capacity of the 10 AWG cable you have installed. Some people have done some pretty poor installs and used crappy wire.

[Sidney777]

As suggested, fuse probably too small

[geekoman]

Yes. Probably didn't blow because the current peaked above 20 Amps, and fuse is slow blow and rode through the peaks.

[Nepidae]

Last July we installed 3-220W Xantrex Flex panels in series. A Victron MPPT 150/60 Smart charge controller is between the panels & the batts, as well as some circuit breakers. IF I could figure out how to post a picture I'd be able to show the setup.

If I remember correctly our wiring from the panel wiring (that had a dual wire and special connectors already attached) to the MPPT and then to the batts is 10g or a little smaller.

The panels are located on a Hard to Top over the bridge and wiring drops straight down to the engine room and then to the batts. A less than 20' run.

BTW, we are a trawler, if that makes any difference.

I'd add, if you aren't sure, bring in a technician who knows what they are doing. You've seen what can occur if you don't know.

Good luck.

[capnorv]

If you don't want to change the fuse and wiring, why don't you wire the panels in series and install a mppt charge controller? Your maximum output would be more like seventy five volts, about twelve amps, end of overload, and the higher voltage will carry the available current much more efficiently through your wires. More important, in less than ideal conditions you will be wringing all the charging current you can out of your system. I've used solar panels since the eighties in both houses and boats, and the change to mppt charge controllers was a true godsend. Try it you'll like it. On another subject, don't expect your panels to put out what they say very often. They are rated on maximum efficiency. A cold day, perfect sun angle, short term exposure. Anything else will be less so having the ability to milk all the available power out of the charging circuit is the way to go. Midday on a minty degree day, you'll be lucky to see seven amps a panel. I usually figure I'll be fortunate to get fifty percent of rated current through the six hours of midday. On another subject, fusing the output of a charge controller is a good way to buy a new charge controller. Always disconnect the panel side before disconnecting the sponge (batteries). I've seen too many sad stories by people doing this the wrong way. Good luck.