House burned down

[Hedges]

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:

https://www.mouser.in/new/littelfuse/littelfuse-mega-70v-sf51-hp-fuses/

"

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.

 

[ricardocello]

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.

LFP Powerwall

@Jejochen it’s a great feeling getting the system up and running. For the bus bar pic is that the Batrium shunt behind it or something else...? Trying to determine if you leveraged a bus bar connector on either end of the shunt. Thanks !

diysolarforum.com

This makes me very sad, the OP had a clean install with lots of fuses that should have worked.

 

[Brett V]

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.

 

[Hedges]

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.

 

[Jejochen]

For obvious reasons i will not be continue on this forum, as life is 1 big chaos right now. Will be back shortly

 

[robbob2112]

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.

Agree with this.

And ABYA recommends battery fuses be within 7 " of the battery terminal.

 

[Brucey]

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.

Maybe the fuse holders? Or what was behind it if it's wasn't steel sheet or some fire resistant backer material.

 

[Brucey]

For obvious reasons i will not be continue on this forum, as life is 1 big chaos right now. Will be back shortly

Good luck with the recovery.

 

[robbob2112]

For obvious reasons i will not be continue on this forum, as life is 1 big chaos right now. Will be back shortly

Good luck, you will return to 20 pages of speculation I am sure.

 

[Boomerweps]

WOW! Just WOW!

Well, the fuse worked…
But the power was high enough to arc over the melted fuse. And that continued long enough to set a fire.
I’d contact the fuse maker. Too short a section that actually melts away from the fuse tabs.

 

[WindWizard]

I sympathize with you. Your build looked to be a professional build looking at your previous post.

When fuses blow, then there is a root cause for the fuse to blow as I found out with my 93 Dodge Ram truck when one of the fusible links blew and the mechanic changed out the link without determining the root cause and it blew again which left me stranded in a very precarious situation.

I know this is hard for you but for all of us in this forum that have their family at risk, the more that we can find out about this tragic loss the safer we will all fill. I have my 110kwhr LFP pack in the cellar of my home. If that caught on fire, then the whole house would go.

I have my Cells divided into two parts with two class t 200 amp fuses to protect the Cells. There are 128 -280 amp Cells. I did not put my Cells in a metal enclosure or compress them. They are on a nice piece of wood. This has really got me thinking about what I can do to protect myself further.

I am thinking about maybe fire blankets or some sort of a fire alarm that can be heard while sleeping two floors above the cellar.

Any suggestions would be appreciated. The simpler the better.

 

[Brett V]

Agree with this.

And ABYA recommends battery fuses be within 7 " of the battery terminal.

Each of my batteries has a 100 amp BMS. The class T fuse is rated at 300 amps but is connected to the positive post of the battery with 12” of 2 gauge welding cable and the fuse holder is screwed to a steel plate on the shelf. The output of the class T feeds 2 gauge cable to a 100 amp midnight panel mounted breaker. The overload on the BMS is very fast and the class T is also a fast acting fuse. The 100 amp breakers are for convenience. I’m thinking I need to replace the class T’s with something smaller. Maybe 200 amp.

This is a reminder that as hard as we try to think of every possible scenario, Murphy never sleeps. I have done all I can and have a smoke detector directly above the battery rack.

 

[upnorthandpersonal]

I'm so sorry to hear about this. As others said as well, really glad no one got hurt!

 

[ricardocello]

I’ve just ordered replacements for all of my 58V-rated MEGA fuses, upgrading to the 70V ones.

https://www.mouser.com/new/littelfuse/littelfuse-mega-70v-sf51-hp-fuses/

I do have a Class T in the battery rack, fortunately.

 

[Mattb4]

Looking back on some photos you had in a previous Thread that had the fuse blocks as well as some of the wiring arrangement. I have to question if an arcing fuse caused the fire. Unfortunately there is insufficient images of your completed system and also the fire destroyed setup to have me concur with the fire inspector as to cause.

 

[Brucey]

I sympathize with you. Your build looked to be a professional build looking at your previous post.

When fuses blow, then there is a root cause for the fuse to blow as I found out with my 93 Dodge Ram truck when one of the fusible links blew and the mechanic changed out the link without determining the root cause and it blew again which left me stranded in a very precarious situation.

I know this is hard for you but for all of us in this forum that have their family at risk, the more that we can find out about this tragic loss the safer we will all fill. I have my 110kwhr LFP pack in the cellar of my home. If that caught on fire, then the whole house would go.

I have my Cells divided into two parts with two class t 200 amp fuses to protect the Cells. There are 128 -280 amp Cells. I did not put my Cells in a metal enclosure or compress them. They are on a nice piece of wood. This has really got me thinking about what I can do to protect myself further.

I am thinking about maybe fire blankets or some sort of a fire alarm that can be heard while sleeping two floors above the cellar.

Any suggestions would be appreciated. The simpler the better.

Smoke detectors can work simultaneously these days, i.e the one in the basement goes off and all the others in the house also trigger.

Biggest issue I've seen is the shelves being made of some thin wood or fiber material and collapsing

 

[Supervstech]

Anyone installing mega fuses in a home system needs to realize they only protect from equipment overloads.
Class T fuses or similar high AIC interrupt are needed to protect from a short circuit.
Shorts can occur at any time with no warning.
Shielding from contact is needed between polarities.
All battery cabling needs to be securely mounted on non conductive surfaces.

Another fire with high capacity batteries. We ALL need to strive to be sure and advise others and ourselves of safety from short circuits and have high AIC interrupt capable fusing in place.

 

[Brett V]

Smoke detectors can work simultaneously these days, i.e the one in the basement goes off and all the others in the house also trigger.

Biggest issue I've seen is the shelves being made of some thin wood or fiber material and collapsing

I have a set of 3 smoke detectors that are linked and if one trips, they all go off and announce which one tripped. Agree that wood shelves aren’t ideal here.

 

[Jejochen]

Also wanna add that we had 6 nest protects in the house, and none gave alarm but after 20 minutes when the house was full of smoke. My son discovered a meter of smoke against the ceiling and woke everyone up. If he hadnt wake up, there would have been 4 funerals this week.

 

[Jejochen]

Also wanna add that we had 6 nest protects in the house, and none gave alarm but after 20 minutes when the house was full of smoke. My son discovered a meter of smoke against the ceiling and woke everyone up. If he hadnt wake up, there would have been 4 funerals this week.

Google is investigating this btw