diy solar

diy solar

So this happened today

After reading the first post my reaction was. "Interesting, I wonder if the system caused the fire?"
When people started immediately blaming the cells my reaction was "but we don't know that!"

Then the eagle eyes of the forum members identified a lot of questionable things:

1) No BMS
2) Wrong bus-bars on the first and last parallel set effectively driving all the current through a single cell.
3) Pos-to-pos and neg-to-neg on some parallel sets
4) No compression
5) Questionable history on the cells. (stored at near zero volts...???)
6) Possibly not LiFePO4
7) Possible mixed metals on the bus bars

I'll add one more:

8) A very large bank of cells that seems to be sitting out in the open and on the floor with nothing protecting the cell terminals and bus bars. Any dropped metal object could turn into fireworks. (I don't like 4 cells with exposed bus-bars..... 70 would make me pucker)

Only #1 in the above list has been confirmed to be the operating mode, but there are enough other oddities to make me think the system was likely involved in starting the fire. Beyond that, it is kinda hard to pin down what happened.
 
That photo is of a partially disassembled battery, with no voltage present. Those cells would need to be removed and charged to be dangerous.
or punctured. they still have dangerous electrolyte (i presume). Not saying the screws wouldve punctured. Just saying that because the batteries were near 0 volts doesn't mean no danger is present.
 
some folks are going to be embarrassed if he comes on here and say that the photo was during (inset operation here) and not the final configuration and that there is no BMS because the pack had not been commissioned yet.

What I am saying is that until the owner enters the ring and gives some answers everything to date has been a WAG.
 
That was just two busbars and one flipped bank away from being a nice battery, maybe. So close.
 
one flipped bank away
I got to thinking about the flipped cell banks and got to wondering what would happen and it turned into an interesting thought experiment.

When you first hook them up and there is no load or charge, the only thing that would happen is that the total battery voltage would be lower than expected but there would be no fireworks. In this case there are two 'mega-cells' backwards so the bank would be ~ 6.4V low.

Once there is a load or charge, things start getting 'interesting'.

If you are draining the battery (load), the 'backwards' cells would actually be getting charged.... running the risk of severe overcharge. However, if the there was a low voltage disconnect on the load, it would cut things off before long so depending on the initial state of charge it might not be too bad.

If you are charging the battery, the backwards cells would actually be getting discharged... running the risk of severe undercharge. Furthermore, the charging system would try to charge the bank to the 'expected' voltage so each of the other cells would have to take on its share of that 'lost' 6.4V. In this case it would be 6.4/14=.457V. Furthermore, as the backward cells discharge their voltage will drop and drive the total voltage further down.....making the other cells see even higher voltage. I don't know if it would continue to cascade or would find an equilibrium..... but it certainly could get really bad on all the cells.

As far as I know LiFePO4 wont spontaneously combust due to over or under charge so I don't think this caused the fire directly..... but like everyone says, this is just more speculation based on precious little data.
 
Wow....to the person who thinks the thread should be "deleted", I think it should be stickied. Of course, once we get more factual details from the owner, or his/her representative who seems to be the person sharing.

The one thing in this whole situation that worries me is the number of people not just here in our forum, but across the internet, that are giving newbies the false sense of security that "LifePo4 cells are 100% safe". First of all, there's no such thing as "100% safe". Drop a 16S pack on your head from 50 ft., lol. But secondly, the truth is that LifePo4 cells are "safer" and that's not the same thing as safe, especially in the DIY battery building realm. Maybe a few of these 'fire situations' would at the very least scare someone into taking a 2nd look at their grand plan, because in the Golf cart world, as an example, I'm seeing folks almost daily making statements like these; "So instead of buying new batteries for my cart, I've decided to build my own lithium set up. Is this AC clamp meter a good choice" to which someone answers "yes", lol. Not that we don't exist to promote the DIY world, but we all need to make sure we're supporting safety first as an ideology. Someone says, "My lifepo4 battery caught on fire" and there's 30 people who quickly jump in and say, "wasn't the cells fault...your cat did it".
 
Most things will burn when heated sufficiently...
If the wiring causes a Hotspot, igniting wiring insulation or building materials, LiFePO4 electrolyte will burn... violently.
But the cells themselves don't burst into flames like lithium ion manganese cobalt cells do...
 
cells themselves don't burst into flames like lithium ion manganese cobalt cells do.
I’ve been to sell windows needing replacement from being next door to houses that burned this summer.
What I learned from my inquiries and the determined origin of the fires? Don’t leave your dewalt, ryobi, Milwaukee- whatever brand- cordless tools with the battery charger plugged in and charging/floating. Laptops and phones less of a concern but all these are little. A huge battery bank can definitely make a shower of sparks for quite some time.
 
I’ve been to sell windows needing replacement from being next door to houses that burned this summer.
What I learned from my inquiries and the determined origin of the fires? Don’t leave your dewalt, ryobi, Milwaukee- whatever brand- cordless tools with the battery charger plugged in and charging/floating. Laptops and phones less of a concern but all these are little. A huge battery bank can definitely make a shower of sparks for quite some time.
That tools use NMC cells. Same as the old Tesla S. Some even build powerwalls from them (a bit dangerous for my taste).
Lot of phones use LiPo cells. That is the most dangerous lithium chemistry. And we put it next to our head :) (and bed)
LFP at least do not explode like NMC does.
And no firehawk:
 
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