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Old 29-07-2020, 10:57   #46
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Re: Electrical Fire - Seeking Help Please

I had a Yanmar 3JH3 where I upgraded it to a 100A alternator. I upgraded all the positive wires, the negative side of the alternator was the ground to the engine, right? Wrong.
There was what they called an isolated ground wire inside the wiring harness. A long under power run heated the ground designed for about 50 A, inside the harness, that shorted out to a sensor wire, told the alternator to do full output on flat batteries. Lots of smoke, but fortunately we shut down early. Harness was toast, but a new one was delivered quickly, the cruise was saved.
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Old 29-07-2020, 11:04   #47
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Re: Electrical Fire - Seeking Help Please

When cables burn/melt, determining the cause of the fire is easy: unsafe and not up to code installation where fuses are not installed or of a value too high for the wiring in use.

That’s it, it’s got nothing to do with the charger. In a good installation, the charger would be blamed for blowing up the fuse, no fire at all
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Old 29-07-2020, 11:21   #48
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Re: Electrical Fire - Seeking Help Please

I think that there was a short in the shore charger between both plus feeds and ground. Because the shore charger is connected to BOTH batteries independent of the switch position, the plus cables shared the current and the minus conducted the full current. So the minus burnt out first.

There are a few problems with the wiring design;

1. When the switch is in the ALL position, the outputs of the shore charger are connected.
2. There should be fuses at the source of any power generating system. Alternator, Panels and charger, as well as batteries.
3. The charging part should be separate from the starting part. Sharing the switch for both parts is incorrect.
4. Running the alternator with the switch in off will probably blow the alternator diodes.
5. Running plus and minus together through points of possible chafe is unwise.
and more.

You need a redesign. What you have now is dangerous in many respects.
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Old 29-07-2020, 12:18   #49
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Re: Electrical Fire - Seeking Help Please

There are four things I would check;
1 Did this start due to a wiring fault, either a poor connection (corroded, loose etc) or damage to insulation.
2 Did something fall (loose spanner etc) and cause a short.
3 Did the shore power charger develop a short and why did the fuses not work
4 Check the off-1-both-2 switch, they commonly develop pitting from small arcs, this increases the resistance and because they are high load can rapidly lead to thermal runaway and them catching fire. Even if that was not the cause this time now would be a good time to swap it for something safer
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Old 29-07-2020, 14:42   #50
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Re: Electrical Fire - Seeking Help Please

Quote:
Originally Posted by gonesail View Post
speaking of wire clips .. plastic would be better than the sharp edged metal. sorry to hear about your problem

The neoprene covered stainless steel clips are the gold standard.


Plastic ones fail over time leaving an unsecured cable.
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Old 29-07-2020, 16:14   #51
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Re: Electrical Fire - Seeking Help Please

Every single B+ wire on a recreational or commercial boat is to have an overcurrent protection device (OCPD-fuse or circuit breaker) where the conductor connects to the battery system. The only wire that does not have to have an OCPD is the starting motor B+. The ABYC Standards require the OCPD to be within 7" of the connection to the power source. There are exceptions. Properly sized OCPD's would have probably prevented this accident.
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Old 29-07-2020, 20:47   #52
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Re: Electrical Fire - Seeking Help Please

I've got 32 years of doing and teaching forensic investigations. Your photos indicate the initial failure was likely within the shore charger, connecting the C1 cable from the main battery switch to the ground wire. The most common cause would be failure of the charger transformer and here's why:

All but two wires/cables show external damage, not internal heat damage. Those two are the ground cable which is missing almost all insulation, and the C1 cable. DC is fairly simple, in following internal damage toward the source of power. In your case, the closest the damage gets to a DC source is where the C1 cable attaches to the back of the battery switch, shown in this photo:



Note that this is the point where the charger cable is a smaller diameter than the battery cable, probably 10 ga and 1 or 1/0 respectively. So here is the source of power feeding into the failure.

The reason a short to ground of the red C1 wire prior to arriving at the charger did not happen is because the damage would be limited to the C1 cable.

In this case, most of the length of the black ground cable has even more extensively internally heated to the point of nearly complete insulation loss. This more extensive heat validates what Jack C wrote, in that at some point current from more than just the C1 was carried by the ground cable.

The reason the red C2 cable from the battery switch is not showing evidence of internal heat damage is because the current from the C1 already would have heated the both the red C1 and the black ground cable and initiated thermal damage in both. (increasing heat increases electrical resistance significantly) Therefore, by the time the C2 side of the charger circuit falilure developed inside the charger, the current through the red C2 cable was leading to where the C1 failure had already created a higher resistance path between the charger and ground. Therefore significantly less current went through the red C2 and you don't have the internal heat damage. (It will actually have damage if you section the wire, but you're going to replace it anyway so this is just academic.)

Within a charger is a transformer which typically has windings for both the C1 and C2 paths, plus the charger will have a rectifier for each. The transformer is where the C1 and C2 circuits come together, plus where they are closest to a path to ground. As discussed above, here is where the initial failure was the C1 circuit to the ground path, creating enough heat to then involve the C2 winding. A rectifier failure is an unlikely initial cause because it would need to be a double rectifier failure and that'd be low probability.

You could try to ask the charger manufacturer for a warranty replacement, but I'd suggest just swallowing the loss if they refuse and get on with life. Trying to go to court or somehow do anything further just isn't worth the cost.




So much for what happened. Note that power was not involving the MPPT or solar system so I wouldn't worry about electrical damage to them.

When I teach forensic classes, I tell students that wires are a lot like fresh brownies. Fresh brownies are soft and have all sorts of properties which interact just right with your taste buds. When wire is made the properties also hit a sweet spot in specifications regarding internal resistance, insulation resistance, thermal capability, etc. The problem with both brownies and wires is that damage is cumulative and never heals itself. If I put the brownies back in the oven at a higher temperature or for a longer time at heat, they become hard or even burn, and it is the same for wires.

Obviously, the charger and cables need to be replaced completely and as so many other wrote, add fuses.

On installation of the new wires and cables, you've now had a great life-time lesson about why designers try to minimize chafe points and segregate:
1. Fuel and flammable sources from high current circuits. In boat systems this generally means keeping the AC and anything heavier than about 14 AWG separated from flammables, especially not parallel above or below.
2. Critical circuits from non-critical. You can lose a battery charger, but would not want to lose the comm or all nav.
3. Etc.

What I would further suggest at this point is to also replace any wire or cable that has any thermal damage to it because they became the over-baked brownies. (Note that thermal damage does not mean those only smoked or sooted. You'll know the difference because those can be cleaned.) Because there may've been high current shorts to co-bundled wires and cables, disconnect every ring terminal and connector related to those to look for blackening or darkened (overheated) insulation adjacent to the connectors and replace any that you find. Then test each of those for function of whatever is on the circuits.

Glad that you got away pretty easy.

Bob
NTSB (retired)
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Old 29-07-2020, 21:47   #53
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Re: Electrical Fire - Seeking Help Please

Quote:
Originally Posted by APWTryfan View Post
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.


Thanks everyone!

Andy
Really sorry to hear of this, and especially at the start of a holiday.
I suggest nothing to do with your panels or overcharging - it is simply a short circuit, where the smaller capacity cable overheated and burnt the insulation.

Certainly there is an issue with protection. Fuses (and thermal breakers) were invented to prevent exactly this sort of thing, and should be in every circuit.
Without being there, a bit hard to see exactly where the short occurred, but if it were me, I would just replace the wiring as it was, but this time with fuse protection as close to the source of current as possible (and that means for example, at the charger AND at the battery bank). Also, at distribution points, where wire gauges change, there should be a fuse or breaker protecting that new run of lighter gauge wire.

The charger is also obviously dead now, and probably not worth repairing - surprised it did not have its own internal protection. Looking at that, if that is the shore charger, then it could well be the point of the short circuit, as normally there would be no current running from/to it.

Hope that helps, and hope you can resume your holiday very quickly.
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Old 30-07-2020, 02:17   #54
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Re: Electrical Fire - Seeking Help Please

I’m not sure that you have a similar problem to what nearly caused an electrical fire on my boat but in case it applies here’s the story.

We were crossing the North Sea in a boat that was new to us in force 7-8 from the quarter. Over the crossing we developed issues keeping the batteries charged for the instruments. We had to run the engine for longer and longer each time. At one point a crew member report smelling an acrid burning smell but none of us could find the cause. Finally the whole electrical system died and we landed up navigating into Gothenburg in the dark using google maps, an handheld gps and paper charts (always carry paper charts!!!!!)

On inspection of the electrics we found a 50Amp fuse that had melted its casing. Apparently what had happened was the boats battery bank up and died during Trip which meant that the 55 Amp alternator pumped as much juice into them as it could to try and recover their voltage. Try as it might that didn’t happen and eventually 55 amp going through an old 50 amp fuse was just enough to heat the fuse to dangerous temperatures without actually blowing it.

We were lucky! It could easily have been a fire in a gale in the middle of the North Sea.

Anyway. If you haven’t already I would check the condition of the batteries. If they are on the outs, the alternator will try to compensate by pumping them with higher currents and that can lead to a fire as it nearly did for us.
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Old 30-07-2020, 02:48   #55
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Re: Electrical Fire - Seeking Help Please

Fuses at the batteries may not have prevented the problem as they would have to be large enough to take the starting current of the starter motor and the short in the charger may or may not have tripped the fuses.
The real problem is the battery charger. This charger according to the manufacturer does not need fuses on the DC output because the output current is self limiting.
See

3) Battery cable wires should comply with ABYC A-20 standards, more importantly is that
each ungrounded DC conductor shall be provided with an over current protection fuse within
7 inches of connection to the DC electrical system or to the battery. The fuse rating should
be 10 to 20 amps higher than the rated full output of the charger. Normally protection would
be necessary at the charger end of this wire but because the ProTech-4 series charger is
self limiting (can not exceed its rated current output) no fuse is necessary at the charger
output. The provided fuse protects the unit against an inadvertent reverse polarity
connection.


The manufacturer states that a fuse is NOT necessary, but it appears that input current is NOT self limiting which resulted in a fire.

So even though the wiring design is questionable at best, in my opinion the problem cause is a design problem of the charger. Either the self limiting on the output failed or it was unidirectional.

Talk to the manufacturer. They should analyse what happened and publish a product warning and recommend that fuses be installed at the DC outputs if they conclude that fuses ARE necessary.

I hope everyone with this charger is as lucky as Andy.
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Old 30-07-2020, 02:49   #56
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Re: Electrical Fire - Seeking Help Please

Fuses at the batteries may not have prevented the problem as they would have to be large enough to take the starting current of the starter motor and the short in the charger may or may not have tripped the fuses.
The real problem is the battery charger. This charger according to the manufacturer does not need fuses on the DC output because the output current is self limiting.
See

3) Battery cable wires should comply with ABYC A-20 standards, more importantly is that
each ungrounded DC conductor shall be provided with an over current protection fuse within
7 inches of connection to the DC electrical system or to the battery. The fuse rating should
be 10 to 20 amps higher than the rated full output of the charger. Normally protection would
be necessary at the charger end of this wire but because the ProTech-4 series charger is
self limiting (can not exceed its rated current output) no fuse is necessary at the charger
output. The provided fuse protects the unit against an inadvertent reverse polarity
connection.


The manufacturer states that a fuse is NOT necessary, but it appears that input current is NOT self limiting which resulted in a fire.

So even though the wiring design is questionable at best, in my opinion the problem cause is a design problem of the charger. Either the self limiting on the output failed or it was unidirectional.

Talk to the manufacturer. They should analyse what happened and publish a product warning and recommend that fuses be installed at the DC outputs if they conclude that fuses ARE necessary.

I hope everyone with this charger is as lucky as Andy.
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Old 30-07-2020, 03:03   #57
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Re: Electrical Fire - Seeking Help Please

Quote:
Originally Posted by Jack C View Post
Fuses at the batteries may not have prevented the problem as they would have to be large enough to take the starting current of the starter motor and the short in the charger may or may not have tripped the fuses.
The real problem is the battery charger. This charger according to the manufacturer does not need fuses on the DC output because the output current is self limiting.
See

3) Battery cable wires should comply with ABYC A-20 standards, more importantly is that
each ungrounded DC conductor shall be provided with an over current protection fuse within
7 inches of connection to the DC electrical system or to the battery. The fuse rating should
be 10 to 20 amps higher than the rated full output of the charger. Normally protection would
be necessary at the charger end of this wire but because the ProTech-4 series charger is
self limiting (can not exceed its rated current output) no fuse is necessary at the charger
output. The provided fuse protects the unit against an inadvertent reverse polarity
connection.


The manufacturer states that a fuse is NOT necessary, but it appears that input current is NOT self limiting which resulted in a fire.

So even though the wiring design is questionable at best, in my opinion the problem cause is a design problem of the charger. Either the self limiting on the output failed or it was unidirectional.

Talk to the manufacturer. They should analyse what happened and publish a product warning and recommend that fuses be installed at the DC outputs if they conclude that fuses ARE necessary.

I hope everyone with this charger is as lucky as Andy.
The wires need to be fused at the point they connect into the dc system. Which here is where they enter the battery switch. No starter current is in the battery charger wires. Fuses would have prevented it. The current from battery is not self limited. Which is why the fuse goes at the battery end, not charger end. If the charger was not self limited. You’d need fuses at both ends.
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Old 30-07-2020, 03:54   #58
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Re: Electrical Fire - Seeking Help Please

I think I am going to put some fuses on my AC charger. I never use it now that I have solar, so have not thought about it in a long time. I already have fuses at the battery, but they are big and may not protect the thinner charger wires adequately.

If it makes the current difficulties any better, please know that you have at least helped others.
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Old 30-07-2020, 04:16   #59
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Re: Electrical Fire - Seeking Help Please

Sorry, do not agree. Fusing must be with 7" of power generating source. The battery switch is almost always further than 7" from the battery.
Yes, No starter current is in the battery charger wires. but in this case the starter is NOT connected directly to the batteries. The switch is wrongly being used to switch batteries to the starter, alternator, panel and charger. Probably why there is a large amperage fuse or no fuse at the batteries.
Yes, a fuse must definitely be at the battery end. But what size fuse? Probably 80 or 100amp because an alternator can push that amount of current into the battery. The fuse is sized per the wiring size and protects the wires. At the panel there is another set of fuses to protect the smaller wires going to the consumption devices.
So what about the battery charger. Typically rated at 20amps for a small boat with appropriate wire size. The battery fuse will not protect the wiring to the charger unless the amps are greater than 80amps or more. In this case we are relying on the current limiting of this charger which should protect the wires against a short between the charger and batteries. In this case the short was in the battery charger, the charger was not working, the current was flowing backwards along the wires and the charger current limiting circuitry did not protect the wires. The current created by the short is dependent on the resistance at the short, the extra resistance caused by heated wires and the capacity of the battery. So an 80amp or larger fuse at the battery will not protect 20amp wires from causing a fire unless the current is higher than 80amps. The most dangerous fires are caused by shorts that generate heat but don't trip fuses. Thats why proper fuse and wiring sizing is extremely important.
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Old 30-07-2020, 04:32   #60
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Re: Electrical Fire - Seeking Help Please

Quote:
The most dangerous fires are caused by shorts that generate heat but don't trip fuses. Thats why proper fuse and wiring sizing is extremely important.
I can testify to this.
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