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House burned down

Jejochen

Solar Enthusiast
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Oct 12, 2019
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167
So, after 4 to 5 years of working flawless, the 100 kwh lifepo4 battery caught fire at night and burned our house down. Luckily our family just made in out on time.
Inspection of the fire expert revealed that a melt fuse melted, and created an arc between the 2 points wich ultimatly started the fire.
So i learned to not use melt fuse anymore, plus once the house is rebuild, i will put the new system in a seperate shed outdoor.
 

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So sorry to hear!!! But thank you for sharing.
The large DC current we deal with needs to be respected.

I am curious, where in the circuit was the fuse, and was the arc across the fuse gap?
 
So sorry to hear!!! But thank you for sharing.
The large DC current we deal with needs to be respected.

I am curious, where in the circuit was the fuse, and was the arc across the fuse gap?
The fuse was just behind the battery bank, as it should be.
The arc was i deed across the fuse gap
 
See my previous posts
 
What was the event that caused the fuse to blow initially?

That looks like 275A and there are a few batteries connected to a bus bar that "looks" a little small for what should be a 1000A bus bar.
 
Sorry to hear this News.
Did you have any Photos of the system before it went up in flames posted on the forum or still on your phone?
 
What was the event that caused the fuse to blow initially?

That looks like 275A and there are a few batteries connected to a bus bar that "looks" a little small for what should be a 1000A bus bar.
Each bank has its own fuse. The system had fuse all over the place, each inverter, each solar charger, each bank etc... but it is one of the fuses of one of the battery banks that blew. The inverters combined could never give more but 15 kw.
What the trigger of the event was, no idea. The expert could only locatie the source. Everything is destroyed.
 
Thank you for sharing this painful experience.
So long as no one was hurt, at least it is only money and memories.

Hope we get to hear about insurance outcome, if applicable.


Mega fuse is rated for 2000 AIC at 32V.


Each bank has its own fuse. The system had fuse all over the place, each inverter, each solar charger, each bank etc... but it is one of the fuses of one of the battery banks that blew. The inverters combined could never give more but 15 kw.

What are the specs of the battery bank?

Obviously if 48V not 24V, exceeds rating of fuse.
If 100 Ah or larger LiFePO4, my estimate (based on reports of measured internal resistance) is 20,000 but actual output could be less.
Based on those figures, I think Class-T (125VDC, 20,000AIC) is appropriate, or higher like 50K AIC for some fuses or breakers.

Good to put them in an outbuilding. We know that is advisable for the more hazardous chemistries, but most people here have felt comfortable with LiFePO4 in their house or vehicle. NEC does allow UL listed ESS in or on a dwelling, but not directly in occupied rooms. Rather a closet or garage, with fire or smoke detector.
 
Sorry for your loss and good luck on the rebuild. The good thing is everyone in your family was OK.

Has an insurance adjuster reviewed everything yet?

Do you plan to use Class T fuses when you rebuild?
 
Thank you for sharing this painful experience.
So long as no one was hurt, at least it is only money and memories.

Hope we get to hear about insurance outcome, if applicable.


Mega fuse is rated for 2000 AIC at 32V.




What are the specs of the battery bank?

Obviously if 48V not 24V, exceeds rating of fuse.
If 100 Ah or larger LiFePO4, my estimate (based on reports of measured internal resistance) is 20,000 but actual output could be less.
Based on those figures, I think Class-T (125VDC, 20,000AIC) is appropriate, or higher like 50K AIC for some fuses or breakers.

Good to put them in an outbuilding. We know that is advisable for the more hazardous chemistries, but most people here have felt comfortable with LiFePO4 in their house or vehicle. NEC does allow UL listed ESS in or on a dwelling, but not directly in occupied rooms. Rather a closet or garage, with fire or smoke detector.
The fuse picture i posted was just an answer to the "what is a meltfuse" question.
The exact fuse was a mega 48v, 300 A.

The insurance is no problem.
 
Thank you for sharing this painful experience.
So long as no one was hurt, at least it is only money and memories.

Hope we get to hear about insurance outcome, if applicable.


Mega fuse is rated for 2000 AIC at 32V.




What are the specs of the battery bank?

Obviously if 48V not 24V, exceeds rating of fuse.
If 100 Ah or larger LiFePO4, my estimate (based on reports of measured internal resistance) is 20,000 but actual output could be less.
Based on those figures, I think Class-T (125VDC, 20,000AIC) is appropriate, or higher like 50K AIC for some fuses or breakers.

Good to put them in an outbuilding. We know that is advisable for the more hazardous chemistries, but most people here have felt comfortable with LiFePO4 in their house or vehicle. NEC does allow UL listed ESS in or on a dwelling, but not directly in occupied rooms. Rather a closet or garage, with fire or smoke detector.
Want to add that in my system i followed all fuse and wire specifications as indicated in the victron manuals.
 
Thank you for sharing this painful experience.
So long as no one was hurt, at least it is only money and memories.

Hope we get to hear about insurance outcome, if applicable.


Mega fuse is rated for 2000 AIC at 32V.




What are the specs of the battery bank?

Obviously if 48V not 24V, exceeds rating of fuse.
If 100 Ah or larger LiFePO4, my estimate (based on reports of measured internal resistance) is 20,000 but actual output could be less.
Based on those figures, I think Class-T (125VDC, 20,000AIC) is appropriate, or higher like 50K AIC for some fuses or breakers.

Good to put them in an outbuilding. We know that is advisable for the more hazardous chemistries, but most people here have felt comfortable with LiFePO4 in their house or vehicle. NEC does allow UL listed ESS in or on a dwelling, but not directly in occupied rooms. Rather a closet or garage, with fire or smoke detector.
There are 58V rated mega fuses for 48V nominal systems. Personally for a 100+kWh bank, I would be using class ts or midnite 125V 250A mnedc 250 DC breakers.

20200919_220558.jpg
 
Want to add that in my system i followed all fuse and wire specifications as indicated in the victron manuals.
I think the problem is the Victron megafuse system is really not enough for massive 48V battery systems, ergo the imminent release of the class t power in:


Personally I'm using midnite DC breaker for the batteries on the power in, and 58V megafuses for the loads on the lynx distributor

Glad you and your family made it out ok.

Too bad the watchmon and shunt couldn't protect.
 
Sorry for your loss.

I have reviewed your pictures from other threads. The bus bars look like they were DIY from pure copper, maybe 2" x 1/8" or 1/4" ... more than adiquate for the job

https://diysolarforum.com/threads/lfp-powerwall.7537/ -- seems to have the most pictures in it.
There is a different thread where it looks like you had a battery vent issue at one point to repair.

Did any digrams or pictures showing more of the install survive? Assuming they are straight out of the victron manual are you able to say which diagram in which manual to look at?

Nothing jumps out except the use of Mega fuses verse class T or other fuses with higher AIC. I guess what I am asking is if there were any DC breakers used?

And is there any way to tell where the melted fuse is in the circuit? i.e. on a battery bank or on some other circuit? Something had to be putting out to much current to heat it enough to melt it but not blow. And at 4pm I assume there was no tinkering or anything going on where it was located?

I didn't see it mentioned, was this in a garage?
 
Last edited:
The fuse picture i posted was just an answer to the "what is a meltfuse" question.
The exact fuse was a mega 48v, 300 A.

Right - my search by name pulled up wrong data.
Using part number I get:


"

SPECIFICATIONS​

  • 70VDC voltage rating
  • 2500A at 70VDC interrupting rating
  • 14 variants of 60A to 500A current ratings
"

The issue here is that 2500A isn't high enough AIC rating for LiFePO4 battery. Even an automotive starting battery puts out 3000A into a short circuit, and 100 Ah AGM puts out 4000A.

We haven't seen a good measured value for LiFePO4, but I think it is 10,000 to 20,000A.
Name brand equipment with lithium inside has something like Class T or better, for instance a 150V 67Ah LG battery I've got (30A max draw)

Also some clarification on timing: it happened at 4 at night. A time when the system is at its lowest activity point.

Strange. Look for signs of a short somewhere (although fire melting insulation could cause a short.)
If battery shorted internally and was backfed, might or might not exceed fuse rating but I wouldn't expect thousands of amps.

Another guy had a LiFePO4 fire at night, multiple strings in parallel. But that appeared to overheat at a battery terminal, not a blown fuse, not a high current event.
 
Mega fuse is rated for 2000 AIC at 32V.
The photo the OP posted in post #7 is a 70V rated MEGA.
The photo @Brucey provided in post #17 shows 58V rated MEGA (I have some of these).
The photo the OP provided previously look like 58V rated MEGA to me.

This makes me very sad, the OP had a clean install with lots of fuses that should have worked.
 
Thank goodness all your people are ok. Things can be replaced, family can not. Your build looked good, it’s going to be difficult to nail down what went wrong. I’m still skeptical of Victrons use of mega fuses, I have a class T fuse close to the positive of each battery.
 
If a fuse arcs, how does this spread to a fire?
I've seen videos of fuses blasting plasma. When in a metal enclosure, the test dummy fares better.
 

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