Fire risk posed by solar panels

[Pelagic]

Originally Posted by andreas.mehlin

Well...
When talking about 12v panels, they don't put out 12v....more something around 18v. So if you would assume a 200w panel put out 100% (which it more or less NEVER does), it would be something around 11A.

Just to clarify using my Specs for 4 of these panels connected in parallel

My rated output voltage Vmpp is 54.7v and current is 5.98A
The NOCT DATA is even more conservative
So what is my risk?

[Yellowjacket]

Some panels put out considerably more than 12 volts. Sunpower 360 watt panels have an open circuit voltage of close to 70 volts, for example, which is stepped down by the MPPT controller to 12V or 24V depending on boat system, with a corresponding increase in amperage.

I've been told by those more experienced than myself that brass terminals are rated only to 48 volts. It's difficult to find a cut-off switch for voltages (ignoring amps for a moment) greater than 48V DC to install between the MPPT and the panels.

I was shipped a breaker from Amazon, supposedly a Blue Seas circuit breaker and 80V DC rated, but when it arrived, the sticker on the breaker indicated it was not rated to 80V DC and the placard in the box said 48V DC max.

Had I installed it, I believe it would have been a potential fire hazard, or worse. Heads up.

[RaymondR]

It's the amps which are the killers, you can generate an awful lot of heat shorting out 12V.

[Yellowjacket]

Originally Posted by RaymondR

It's the amps which are the killers, you can generate an awful lot of heat shorting out 12V.

I thought so too, and they are, but exceeding the design DC voltage of kill switches and circuit breaklers is also a hazard, so I've been told. But I'll let the more knowledgeable weigh in.

[Pelagic]

Originally Posted by Yellowjacket

Some panels put out considerably more than 12 volts. Sunpower 360 watt panels have an open circuit voltage of close to 70 volts, for example, which is stepped down by the MPPT controller to 12V or 24V depending on boat system, with a corresponding increase in amperage.

I've been told by those more experienced than myself that brass terminals are rated only to 48 volts. It's difficult to find a cut-off switch for voltages (ignoring amps for a moment) greater than 48V DC to install between the MPPT and the panels.

I was shipped a breaker from Amazon, supposedly a Blue Seas circuit breaker and 80V DC rated, but when it arrived, the sticker on the breaker indicated it was not rated to 80V DC and the placard in the box said 48V DC max.

Had I installed it, I believe it would have been a potential fire hazard, or worse. Heads up.

When calculating the wiring and breakers for my 4 x Sunpower 327, this is what was reviewed with a Solar consultant

SUNPOWER pv is
327wp x 4 = 1308watts
vmp - 54.7 vdc. voc - 64.9vdv
imp - 5.98a isc - 6.46a

@ parallel Connection 54.7@ 25.84a(isc).
25.84a x 1.56 = 40a
80a mppt x 1.25=100a or (125a available @ the market).

BREAKERS recommended Between panel and mppt
Suntree rated @ 40a vdc
Mppt and Battery
Tomzn rated @ 125a vdc.

Which I installed

[clownfishsydney]

I had a controller short out and melt but did not catch fire. Poor design with positive and negative wires entering the controller very close to each other and no way to totally isolate from the other to protect movement and/or wear from vibration.

[sailorboy1]

solar is like any other power source and system

size the wires and connections properly for low voltage drop to reduce heat

I sizzed mine for less than a 3% voltage drop at max current (which it rarely sees) and have a fuse at the battery to protect from the high potential battery

[valhalla360]

So can you provide some statistics?

I haven't heard of any solar specific fires, so is there really a problem related to solar panels or just normal electrical issues.

[thomm225]

The most current I have seen with my "large" panels ( a 65W and 50W) in parallel is 3-5 amps. Voltage 18-21. This on the Victron Monitor w/laptop

So the 14 gauge wire I found and am still using works fine. The 50 watt panel is a Renogy and has their standard size wire, connectors, and a 8' extension. Looks to be 12 AWG

In the early am, I will sometimes aim both panels at the Sun as it clears the horizon to recharge my two 12 volt batteries which are down a bit from running an AC Fan all night.

During the day, usually only one or two panels out of the four I have (65, 50, 20, 20) will be receive totally sunshine. The 20 watt panels are in parallel going to a PWM Controller

Batteries are fused to the load(s) but not to the controller/panels.

I'm still experimenting with the my solar and battery setup

[a64pilot]

I’m glad this came up.
Here in George Town apparently in the last 30 days there have been three cases of flexible panels starting Bimini fires, and as a guess that may have been what set the boat alight that burned to the waterline recently as the story I head was he was listening to headphones while sitting in the the cockpit and suddenly the Bimini was on fire.

A little research shows that many of the house fires may have something to do with leaves etc building up beneath and around the panels.

It would seem that panels are subject to a cell failure that causes an internal short, the internal short of course causes excessive heat and of the panel is laying on something flammable or has flammable material around it, you have a fire of course. If there is nothing close to burn, then it’s just a failed panel.
It would also seem that flexible panels, are more likely to have a cell damaged, can sometimes be made from flammable materials, and are more likely to be laying on flammable materials than hard panels.
Of course a few cases may be poor installs, chafed wiring, looses connections and the like that are unrelated to the panels themselves.

Still 1% or more of boats at anchor having failures that result in overheats in one month is excessive.


All of this is supposition of my own, so take it for what it’s worth.

[FlyingScot]

Every source of power on or to the boat carries some risk. The key is to minimize it. But in the end, there is still some risk. So either learn to live with less power, or accept some risk.

Generators create heat and CO. (and noise that might anger other cruisers).
Shore power connections overheat and melt. Shore power connections also contribute to galvanic corrosion.

It seems rigid panels on metal frames would be the absolute safest.

Whatever route you take, use good quality components and wire them up properly. Also consider the controller charge settings to ensure you don't melt your batteries.

Personally, I don't plug in to marina shore power and feel very safe with my 1440 watt solar setup. I only use a Honda 2.2k as backup power. Preferably only using occasionally to run fresh gas through it.

[Cpt Pat]

Originally Posted by Jammer

There have been a number of solar panel fires at commercial solar installations. A few fires and some near misses have occurred on boats.


A number of solar panels have been recalled by their manufacturers due to fire hazards, including Renology flexible panels and some Bosch rigid ones.


There have also been a number of fires originating in combiner boxes on systems where these are used.


Have you made any changes to your solar system to address fire safety? Beyond ordinary care and electrical best practices, were there any steps you took during the design, selection, and installation process to mitigate fire risk?

Here's a risk I've personally seen:

Ten small flexible panels, each rated at 15 watts (about 1 amp short circuit current output). The interface wires (outputs) are 20 AWG wire. The leads are short (less than a foot) and are intended to be connected to a bus with larger gauge wire.

No fuses - just direct connections to a terminal strip. The entire PV bus also has larger panels: two 65 watt panels. The total PV bus capacity is 270 watts.

One small PV panel then short-circuits internally when someone steps on it, and the ENTIRE output of the PV bus (about 20 amps) flows through the pair of 20 AWG wires and the thin aluminum cell interconnects inside that panel. The panel is coated with a non-skid plastic that isn't flame retardant.

Poof! Smoke and fire. Correction: install 2 amp fuses in series to each small panel. A 15 watt (22 volt open circuit voltage) panel should NEVER see 2 amps flowing through it.

Panels should be manufactured with internal fuse links, but since those links might reduce output by a few percent due to series resistance, it isn't done. I consider the omission of series fuses to be an industry-wide manufacturing defect that has to be mitigated by the consumer with external fuses.

I recommend installing a fuse in series with the output of EVERY panel in an array. The fuse should be sized to a maximum of twice the short-circuit output rating of the panel. Yes, it'll result in a loss of a few percent in usable output.


Installing Schottky steering diodes in series with each panel to block current from the bus flowing to any individual panel will also work, but the loss (about 0.3 Volt) may be greater than the loss through a fuse (but it'll also eliminate reverse current losses). Diode can also short from a serious reverse polarity transient pulse (think lightning), so I don't recommend diodes in place of fuses.

[sailorboy1]

Has anyone ever seen a MC4 connector with a built in fuse????

[Pelagic]

Not all panels are made with the same quality controls

This is why I like Sunpower

https://youtu.be/kdi-qmhCLgI

[GordMay]

Greetings and welcome aboard the CF, JJDPHD, btlflpztk, StevenM, and lhusty.