New Years Surprise, Burnt Solar Wiring

The controller terminals are typical and the wires look ok to me based on how the battery wires are done and attached

. I always have trouble keeping the positive and neg wires apart at those little terminals being so close together with tiny strands escaping the wire and going next door, but Mr Wiz is doing way better than that by having proper lugs etc..

Which leaves the neg panel wire coming loose in its terminal somehow (stripped screw?) with heat melting the plastic barrier between it and the pos terminal lug next door.

The controller might still be ok. If not, ISTR Mr Wiz says it sometimes clips his amps at the 25a limit, so he could use a 30.

Another way is to use two 20s ( Eco-worthy MPPT at $102 each is one choice) and split his array. I would use the (or two) $35 PWM Solar30 instead of MPPT where Mr Wiz has those roof panels that must get very hot, where heat reduces MPPT amps so much.

If it is hot enough there now, it would be a good chance to see if the PWM gets as many or more amps in than the MPPT did before deciding.

ISTR Mr Wiz was thinking of swapping out some of his roof panels if a good deal came along that would give him higher amps for the same real estate. Two controllers would provide for that if it happens.

If you have two different kinds of batteries you can have one solar set on each with different charging profiles to suit. My T-1275s and the GC2 6s did not do well on the one solar set, where the T-1275s wanted more and that made the 6s get overcharged each day. Be the same with AGMs and Wets I imagine.

I have the same problem of the controller program dropping to Float when I want it to stay at the higher absorption voltage longer. Luckily the float voltage is also adjustable so I just set it as high as the absorption voltage, but Mr Wiz can't do that with his spare controller.

The Solar30 has only one adjustable voltage but once the batts get to that it stays there till dark, no dropping to float. If you are in storage and want a float voltage, you just set it for that instead of a higher number as when camping.

The Eco-W has two adjustable settings but the Float high limit is 14.4, so you can't set it to the same as your higher limit Vabs if desired. Even so, I find the 6s like 14.8 and then 14.4 the rest of the day, so it works out. The T-1275s wanted more of that 14.8 good stuff each day though. The Solar30 was more suited to look after them.

Ouch!

My first thoughts seems like the cables are too big for the terminals. By the time you reduce the wiring down to fit the terminals you may end up with some resistance. I always try to use a strong power crimp on the terminal lugs and if they still don't look good will sometimes add some solder. Solder to me is great to keep the strands more controlled. I know some install techs don't like to use solder.

If I run into this when I finally get going with my solar panel install I will most likely be using some of the good BLUE SEA high current terminal blocks for the large cables and maybe run some short lengths smaller cable runs between that terminal block and the low wattage controller terminal strips. Knowing me this may also be the BLUE SEA four position high current switches where i can do my panel combining and on-off state as needed.

Not knowing what is on the RED cable and the BLACK cable it might be they may have touched each other with small strands in the connectors. If RED is HOT and BLACK is GND that would definitely cause some smoke...

Hopefully the larger controllers have larger terminals...

On the other hand it is noteworthy that you have proof you have some 'fire in the wires' coming from your solar panels haha...

I'm looking forward to maybe get started in my solar panel upgrade this coming season. Been saving my jelly beans...

Roy Ken

Hi Mr Wizard,

An unfortunate start to 2015 for sure!

I'd go for 45 amps myself.

+1 on DrewE's comments. Crimps, wire, connection in general looks poor in hindsight.

Is that 105C insulation? Resembles speaker wire more than solar.

Is it my imagination, or are many of the strands of the (formerly) black wire broken just above the crimp connector? If so, that's likely the cause of the problem—assuming things didn't get hot enough to melt or at least greatly weaken the copper, which seems probable to me. (Copper melts at a bit over 1000°C, though as is typical for metals it gets a lot weaker as it approaches the melting point.)

Heat comes from to much resistance which implies poor connection or undersized wire or terminals. I suspect this didn't happen in one day. As I recall you have a good sized solar system with high current with parallel panels. Can't tell from the pic but the terminals if not the wire do not appear adequate.

It looks like the heat emanated from the screw terminals. So probably either the connection was loose (maybe the crimps) or they're just too small to carry the load.