HughF
New Member
In my opinion, yes….
House burned down
- Thread starter Jejochen
- Start date
WindWizard
Solar Enthusiast
The only answer that makes sense to me is that one of his LFP banks had a defective Cell. The result would be that all of the other LFP banks would start to dump their power into the bank. I can think of no other reason for a fuse to arc. The current needs to go somewhere.
seneysolar
Solar Addict
Agreed, this seems the most likely.
So maybe I don't need to be so worried about going to a metal case since I have both class T and stupid honkin' big MCCBs. Between them nothing should blow up.
But I might do the metal boxes just so these darn things are finished already...
But I might do the metal boxes just so these darn things are finished already...
Yes, that was my reasoning as well. A cell fails, the other packs dumping massive amounts of current into the pack, the fuses not able to handle it/arcing, cells (or even just one) venting, and the arcing fuse igniting the vent gasses. If the current was high enough, probably none of the fuses on the different packs would be able to quench the arcs (which is why a high AIC is required for these). I do wonder how that high of a current could develop even with a single cell shorted. I also wonder what the BMS was doing...
Of course, this is all speculation on available data, but I think it's a useful thing to do.
For reference, I have shorted two parallel 48V LFP packs in the past (on purpose). Both the JK BMS on them and the Class T fuse were able to deal with this. I even bypassed the BMS at one point to see how the Class T fuse would handle it on its own. It was essentially a non-event.
Of course, this is all speculation on available data, but I think it's a useful thing to do.
For reference, I have shorted two parallel 48V LFP packs in the past (on purpose). Both the JK BMS on them and the Class T fuse were able to deal with this. I even bypassed the BMS at one point to see how the Class T fuse would handle it on its own. It was essentially a non-event.
So sorry to hear about your loss. Ive had 2 fires in my life, neither destroyed my home, and they were awful.
Free advice, hire an independent adjuster when dealing with your insurance company. Well worth whatever they charge.
Free advice, hire an independent adjuster when dealing with your insurance company. Well worth whatever they charge.
Yes a private adjuster. Extremely important
Cell failure was my initial thought also. BUT in that case the fuse would need to be rated only for 3.4 volts as only one cell of the pack would fail and pack voltage would differ only by 3 volts from other packs. Sustained arcing is pretty unlikely if not impossible with 3 volts, electric arcs typically need 15-20v minimum.
Fuse could still provide as a ignition source for gases. I’d also take the fire investigation results with a grain of salt, everything seems pretty toasty..
Ampster
Renewable Energy Hobbyist
In a Lihium pack it is the current potential that matters. The voltage potential across each cell is still the pack voltage, just as it is at any other point in a series string. Voltage adds in series. The only place where the cell voltage is that low is the BMS sensing wires.
I believe that what he meant was that if one cell shorts, the pack voltage drops with 3.2V, meaning a potential difference of 3.2V between that pack and the others in parallel with it.
Exactly.
Quattrohead
Solar Wizard
If a single cell fails short, I cannot believe that enough current will flow for long enough to start a fire.
Between the BMS and fuse/CB, it should be taken care of.
Between the BMS and fuse/CB, it should be taken care of.
houseofancients
Solar Wizard
Again, this is not about the BMS....
bolhuijo
TechnoGeezer
What if 1 hot cell started melting the plastic wrapper, shorting 2 cells case-to-case? A chain reaction could commence shorting one to the next as the heat grew.
Has anyone actually verified that the case is a direct connection to one of the electrodes? I tested the original EVE 280 cells way back when, and that was just a capacitive coupling, there was barely any current flowing from case to terminal. I have tested this with other cells as well, with the same result, but this test was not exhaustive. Which cells have a direct connection between one of the terminals and the case?
robbob2112
Doing more research, mosty harmless
I think before I would do that I would either go to a fireplace supply house or a place that sells kiln bricks and use them.
houseofancients
Solar Wizard
And to add, this is now the third time we've seen something like a fire or a burn where this BMS was involved..
The first one : cheap powerwall, not build according to spec and leaky cells, yet the BMS was blamed at first
Second one, was a axepium box ( mason 280k rebadge)
Turn out a manual instruction issue and missing crush rings..
Again BMS was blamed until details came out
Here we don't know what exactly went down, and it is all speculation..
Weather this was an internal shorted cell or a fuse that arced, or simply wrongly assembled packs...
Untill we have more info we will not know, but it is all too easy to blame the BMS yet again, most likely wrong again
robbob2112
Doing more research, mosty harmless
The pictures only show 6 strings, but in the build string where he replaced the leaking cells he shows where he had 7 strings made with 112 280ah cells. Also if you read the whole thread where he is building out his battery banks he started in a black metal cabinet then moved to a long wall of cells.
So 7 strings * 16 cells all using cell top balancers controlled by a single BMS. Interesting way of doing it but has the benefit of one controller keeping all 112 cells balanced. And the balance leads don't need any special identical length because the cell top balancer just lets through enough current to do the job. I believe he is using a 2 amp model of this.
I agree it was likely a venting cell that caused overcurrent to blow a fuse that caught on fire providing the spark.
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I'm not blaming the BMS.
I'm just saying I don't want a Seplos BMS for other reasons.
robbob2112
Doing more research, mosty harmless
He is not using a traditional BMS.
Everyone should read this entire thread before commenting on the BMS or other things to do with the battery cells.
LFP Powerwall
a few pictures of my own built 'home energy system'. I run my house, workshop and if needed charge my tesla model S with it. currently 3 multiplus 2 5 kVa units for 3-phase system, 48 V battery: 3 banks of 16 200 Ah cells, monitored by batrium. The victron system runs the ESS template. One of...
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