Electrical Fire - Seeking Help Please

[APWTryfan]

Hello,

We had an electrical fire on our boat this weekend and I was hoping to get an understanding of what happened and prevent this from ever happening again.

We have a C&C33-2 with Yanmar 2GM20 and 200W solar through MPPT controller.

Here is a summary of events…

1. Hot sunny day on Saturday so batteries were fully charged through solar
2. Started motoring at 5pm to our next destination
3. Solar panels were connected (multiple charging sources)
4. At 7pm ever so slight whiff of burning I immediately opened cockpit locker and a boatload of smoke started billowing out, and I quickly shut down the engine
5. Never used fire extinguisher as I saw no flames but had it ready – it took about 20 minutes for the smoke to begin to slowly dissipate

What burned (and didn’t)…

1. The wire from shore charger to #2 pole on Off-1-Both-2 switch (I think the whole wire fried instantly)
2. The ground wire from shore charger to engine
3. Hot and ground wire to shore charger was higher gauge (path of least resistance?) than all other connections to switch
4. There was some collateral damage (refrigeration wires, 120V hot water, few other wires)
5. No damage to batteries / house / panel or any of the other electrical systems

I have attached the wiring diagram for the boat which shows the exact configuration and the makes and models of all components. I am not 100% sure about the alternator.

Click here for a link to photos and videos of the damage.

My current priorities…

1. Fully understand what happened and how to prevent again
2. Salvage what is left of our holiday (we were 2 days into a 2-week trip)
3. Share experience with others to hopefully help prevent this from happening to others

What I have done and intend to do…

1. Identified and removed all wires and cleaned up the mess
2. Rewire the refrigeration
3. Replace other compromised wires (not overly significant as far as I can tell)
4. Never run with solar panels plugged in again

My synopsis (please advise)…

1. Multiple charging sources?
2. Improper voltage regulation?
3. Lower the MPPT float(?) charging voltage
4. Better quality MPPT controller?
5. We have run the engine with solar panels plugged in before without issue - maybe after fully charged hot day this was the problem.
6. Alternator? No wires burned to alternator. I thought that if the battery banks are full then both alternator and MPPT would reduce the charging amps.

I hope I have provided enough detail – please go easy on me as this was rather traumatic.

My wife, 11 year old daughter, dog and I were 10 miles from land, 30 miles from home with no wind. Fortunately, the forecast for the night was 15-20 from northwest for that evening and I have a boat that can sail relatively efficiently upwind. We ended up dropping the hook outside the harbour at 4am Sunday and are now at the dock.

I am hoping for meaningful responses that can help me understand what happened and hopefully help others too. I was amazed at how instantaneous the electrical fire was – my wife and daughter were down below and had to go out the forehatch. Fortunately, she was able to get to one of the fire extinguishers (good to have 3 on boat in different locations) and we didn't have to use it.

Thanks everyone!

Andy

[rslifkin]

So the only wires that burned were the wires to the shore charger? And everything else is still working as expected? Any apparent damage to the shore charger? And does the charger still work?

It almost sounds like the shore charger had an internal failure and shorted to ground. The shore charger hot wire should be fused at the battery switch end when you put things back together. Fuse for a bit higher than the charger rating, but below the wire rating.

Personally, I doubt having the solar online while motoring had anything at all to do with your incident.

[Kelkara]

First of all ... you haven't mentioned fuses anywhere. A fuse wouldn't have prevented this problem from occuring, but it might have prevented the fire that developed as a result. So high on my to-do list would be to check that all wires are correctly fused for next time.

[APWTryfan]

Originally Posted by rslifkin

So the only wires that burned were the wires to the shore charger? And everything else is still working as expected? Any apparent damage to the shore charger? And does the charger still work?

It almost sounds like the shore charger had an internal failure and shorted to ground. The shore charger hot wire should be fused at the battery switch end when you put things back together. Fuse for a bit higher than the charger rating, but below the wire rating.

Personally, I doubt having the solar online while motoring had anything at all to do with your incident.

Yes thanks - just wires from B2 battery post on switch to shore charger, and the ground from shore charger to engine burned. Solar is led to B2 house (also connected to B2 battery post on switch). I'm assuming shore charger is toast.

[rslifkin]

Originally Posted by APWTryfan

Yes thanks - just wires from B2 battery post on switch to shore charger, and the ground from shore charger to engine burned. Solar is led to B2 house (also connected to B2 battery post on switch). I'm assuming shore charger is toast.

Based on that, I'd pull the shore charger and test it. If it's toast, that's most likely what failed and cause your issue. Re-wire with fuses between B2 and each charging source so that if one fails like that and feeds current the wrong way, it can't cause a meltdown.

[APWTryfan]

Originally Posted by rslifkin

Based on that, I'd pull the shore charger and test it. If it's toast, that's most likely what failed and cause your issue. Re-wire with fuses between B2 and each charging source so that if one fails like that and feeds current the wrong way, it can't cause a meltdown.

Thanks for this. I will replace shore charger for sure and will open up the old one to see what's going on. Just to be clear we were running and boat was not plugged in.

I will also recheck fuses and other leads. I never saw a fuse, however, on the shore charger wire whilst removing the mess. No fuse on B1 to B1 switch post and B2 to B2 switch post - those will be significant fuses but as you suggested necessary to prevent fire.

[Turtle Blues]

Looking at your photos yes it would appear that the ground wire was carrying a heavy load at high resistance and started melting the bundle. Per your diagram the B side and several other wires terminate at the engine ground. What did that look like? Possible it loosened under vibration? Agree with suspecting the charger circuit. It seems to have taken the biggest hit.

[Thumbs Up]

In the second photo it looks like the remains of a metal clip that was used to bundle the battery cables. It looks like that clip chafed through the insulation of both cables and created a dead short.

[barnakiel]

One of your wires got converted into a bulb filament.


If the culprit is the shore charger, then this may happen if the wire shorts thru an un-grounded housing (often steel or alloy).


However, to become a bulb, a wire needs to have no fuse along the way.


What happened to the fuse then?


barnakiel

[Statistical]

From the photos and description you had an uncontrolled flow from DC+ to ground between the battery switch and charger. The two most likely scenarios are a short developed in the wiring or the shore charger failed internally. Of the two I think the wiring is more likely. Years (decade?) of the wiring moving and rubbing against the clamps could eventually wear through the insulation.

A fuse on the DC+ wire going to the charger would have protected your wiring in both scenarios. Your first indication of a problem would be no charging when you connected to shore power. I am not saying that to attack you just something to consider when you rebuild after this incident. Glad your family is ok.

[Lake-Effect]

Agree with others that solar was not a factor. I haven't looked at the pix, but from the description it seems pretty clear that there was a short on the charger wires. Please report back as to whether it was the charger, or a physical short somewhere.

Anyway the fix (... besides replacing everything that burned) is to fuse the positive wire of the charger up close to the 1/2/both/off switch. This fuse's job is to protect the charger wiring from the massive currents possible from the batteries if there's ever a short on the charger wires.

(Bah, that'll never happen, right? )

[Frankly]

In a previous life I did two similar insurance boat fire investigation. Both were caused by battery chargers that were connected directly to battery systems. The battery chargers had cicuit protection on the charger end but nothing on the battery end. Shorts occured in the connecting wiring and the 30 amp charger wiring was exposed to hundred of amps flowing back from the batteries.

The normal tunnel thinking is circuit protection at the current source (battery charger). Works fine until a short develops in the wiring an now the source is the batteries. Charging needs to be fused on both ends. Solar and alternators are usually not the same as they are current limited on the normal source end.

One system was factory installed one owner installed.

Frankly

[APWTryfan]

Originally Posted by Turtle Blues

Looking at your photos yes it would appear that the ground wire was carrying a heavy load at high resistance and started melting the bundle. Per your diagram the B side and several other wires terminate at the engine ground. What did that look like? Possible it loosened under vibration? Agree with suspecting the charger circuit. It seems to have taken the biggest hit.

Thank you - the only engine ground wire that burned was connected to the shore controller.

[stormalong]

That is a lot of damage. Probably a wiring short. You have so much secondary damage that every wire that shows any damage should be removed or at least disconnected before using anything on the boat. If that makes your essential systems inoperable fix them before continuing on your vacation.

That might sound harsh but you and your family's safety is at stake. A repeat fire could be a killer. Once fiberglass starts burning it is almost impossible to put it out.

[APWTryfan]

Originally Posted by Thumbs Up

In the second photo it looks like the remains of a metal clip that was used to bundle the battery cables. It looks like that clip chafed through the insulation of both cables and created a dead short.

Thank you - that was a good observation - however none of the clips were metal it only looks that like that I think because of the heat damage.