diy solar

diy solar

So this happened today

He probably would have caught one mistake at the end of the string but two mistakes made the ends come out right. My gut feeling says it just wouldn't work, not start a fire. We should work out the math on how much juice could flowed through the tiniest bottleneck. If even possible, how much would it take and what would happen if you forced flow backward through cells? What reverse voltage (charging) did those cells see?
I think the issue is that it's a 7S pack because of the ++ -- (10p) connection in the middle. He would have been trying to charge at 8s voltage, and could have easily overcharged, especially with the mis-matched parallels, and no BMS ?‍♂️. All this of course is assuming that the black dots mean either positive or negative, I don't know that for sure and can only assume.

I think the mistake at the beginning would have only severely limited capacity and usability to the lowest cell. The voltage should have been the same and overcharging "shouldn't" have occured (of course there's no BMS either). Will did a test of an active balancer where he put different capacity cells in series; it worked, and I don't think it was a fire hazard. However the capacity is limited to the smallest cell in the series, which in his case would have been the single cell at the beginning and ends of the pack.

Again, that is assuming that he didn't add another bus bar before he hooked the pack up at the end, he very well could have put one on when he hooked up the charger / loads.
 
I think the issue is that it's a 7S pack because of the ++ -- (10p) connection in the middle. He would have been trying to charge at 8s voltage, and could have easily overcharged, especially with the mis-matched parallels, and no BMS ?‍♂️. All this of course is assuming that the black dots mean either positive or negative, I don't know that for sure and can only assume.

I think the mistake at the beginning would have only severely limited capacity and usability to the lowest cell. The voltage should have been the same and overcharging "shouldn't" have occured (of course there's no BMS either). Will did a test of an active balancer where he put different capacity cells in series; it worked, and I don't think it was a fire hazard. However the capacity is limited to the smallest cell in the series, which in his case would have been the single cell at the beginning and ends of the pack.

Again, that is assuming that he didn't add another bus bar before he hooked the pack up at the end, he very well could have put one on when he hooked up the charger / loads.
In addition to the black dots, the terminal insulators are also black… pretty definitive polarity indications.

I really feel for this pack.
0V ? Never charged? Please explain.
Did the fire START at the batteries? Or did the house burning take out the pack?

if the batteries were wired this way, they could have combusted themselves from self discharge…
 
I thought about this while doing chores today.....

I'd rather see post like this deleted until/unless more information is posted.

I had a friend get burned badly a few years ago when a Propane bottle blew up... We had a trailer/RV burn down last winter in town due to a heater plug in/fell asleep. Six years ago a good friend burnt down his home due to a plug in heater connection.

Given that the system had no BMS and we don't know much about it (barely anything) assumptions can run rampant. Is this what DIY solar needs? Lots of speculation? But this is why I've yet to build my own. I realized early on I wanted them encased in steel with BMS's and the ability to check them out from time to time (to check their health).... And that for me to do all of that meant little cost savings over prebuilt. And if you factor in a burnt down home/trailer the cost savings went away and maybe your life.

The battery is one aspect of DIY...

On top of it, as we've seen lately, getting anything shipped means damaged shipping. My last 4 decent size shipments have all been dented/damaged to some degree with 3 being unserviceable. Factor in total loose of this coming from China and the extra work...

But to each their own. Mileage may vary, so they say.
 
I'd rather see post like this deleted until/unless more information is posted.
I had a friend get burned... Propane bottle blew up... We had a trailer/RV burn down... due to a heater plug... friend burnt down his home due to a plug in heater connection... we don't know much ... assumptions can run rampant.
we've seen... damaged shipping. But to each their own. Mileage may vary, so they say.
Abstractions are what separate us from the animals. Words are a great time saver. Don't have to learn everything first hand. Safer too.
 
In addition to the black dots, the terminal insulators are also black… pretty definitive polarity indications.

I really feel for this pack.
0V ? Never charged? Please explain.
Did the fire START at the batteries? Or did the house burning take out the pack?

if the batteries were wired this way, they could have combusted themselves from self discharge…

The Cells are being sourced from these large batteries.

image2 (4).jpegimage1 (4).jpeg

When he opens these crates for the first time, all of the cells are at nearly 0V and require charging.
 
The crate says "Lithium-Ion". The Storage Power Solutions website says they make LiFePO4. I don't want to jump to any conclusions, but if those are really Lithium Ion then that's not good.

I don't think it helps, but here is the "Power" tag from the crate.

1629138017097.png
 
That first picture may explain it .... That plus the mistakes we've seen.

We have been assuming these are LFP cells, but if they are actually lithium ion .... they aren't near as forgiving .... and will catch on fire if overcharged.

Edit: .... oops HRTKD must type faster than me.
 
When they are at 0V they are broken, dead, over discharged, ready for the recycling bin.
They are not discharged to 0v, they are uncharged at nearly 0v. New old stock. I reacted the same way initially, but that is just the way these crates came. Something to do with shipping and high voltages, iirc
 
they are uncharged at nearly 0v. New old stock.

New old stock (stored battery) is done at 50% state of charge. Shipping is done at 50% state of charge or thereabout. Storing a LiFePO4 at 0V kills the battery. A completely depleted LiFePO4 goes to 2.5V and will still recover to close to 3V from that, but even at that SoC it will be damaged if stored too long. 0V is a dead battery - it's impossible due to the internal chemistry to be at 0V, and even if you are, and somehow manage to recover from that, you will be at severely limited capacity.

This is why many 18650 cells have a protection circuit: they will disconnect the cell from the terminal at low state of charge to prevent damage. You don't actually measure 0V of the cell; the actual cell is still at 3V or thereabout. I doubt these cells you are talking about have a protection circuit built in, so you measure the cell voltage - and again, at 0V, they're dead Jim.
 
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New old stock (stored battery) is done at 50% state of charge. Shipping is done at 50% state of charge or thereabout. Storing a LiFePO4 at 0V kills the battery. A completely depleted LiFePO4 goes to 2.5V and will still recover to close to 3V from that, but even at that SoC it will be damaged if stored too long. 0V is a dead battery - it's impossible due to the internal chemistry to be at 0V, and even if you are, and somehow manage to recover from that, you will be at severely limited capacity.

This is why many 18650 cells have a protection circuit: they will disconnect the cell from the terminal at low state of charge to prevent damage. You don't actually measure 0V of the cell; the actual cell is still at 3V or thereabout. I doubt these cells you are talking about have a protection circuit built in, so you measure the cell voltage - and again, at 0V, they're dead Jim.
I am aware of this, and again, that is how I reacted. The guy who currently has crates of them, and burned his trailer down, insists that they are coming out at nearly 0v.
 
I am aware of this, and again, that is how I reacted. The guy who currently has crates of them, and burned his trailer down, insists that they are coming out at nearly 0v.

The only thing those crates are then good for is to send them off to be recycled, unless it can be determined that they have an internal protection circuit (which I highly doubt and have never seen on this type of cell - the electronics would be quite substantial). It would be quite a feat to have them all at 0V though - how long have they been sitting in storage? Were they stored in a temperature controlled environment? Let us know if you have details...
 
He bought them in crates this year. Apparently a string of about 40 in series comes out of the crate at something like 3v.. so very very very low voltage in storage. They have never been charged, not once. The project that they were manufactured for was cancelled years ago. I have no idea how they were stored, but it would have been a warehouse somewhere most likely.

When he removes these cells and charges them, 33% or so of the cells behave perfectly, with good capacity and everything seems fine. The other 66% or so have varied results, many of the packs bloating when charging. As you may have surmised, the lot were purchased for very cheap, and are not supported by the company at all.
 
He bought them in crates this year. Apparently a string of about 40 in series comes out of the crate at something like 3v.. so very very very low voltage in storage. They have never been charged, not once. The project that they were manufactured for was cancelled years ago. I have no idea how they were stored, but it would have been a warehouse somewhere most likely.

When he removes these cells and charges them, 33% or so of the cells behave perfectly, with good capacity and everything seems fine. The other 66% or so have varied results, many of the packs bloating when charging. As you may have surmised, the lot were purchased for very cheap, and are not supported by the company at all.
Did the company who sold them stress/emphasize the dangers of the expired product they sold?

Did your friend really understand the risk he was taking?
 
After reading this whole thread, I’m left hoping the builder will give us more details but have a feeling he might not even recall all the details of the build. The fire could have been anything, even conductors or other components. All we really know is something hot made contact with something flammable. Fortunately no one, including the firefighters, were injured. That’s one big positive, anyway!
 
After reading this whole thread, I’m left hoping the builder will give us more details but have a feeling he might not even recall all the details of the build. The fire could have been anything, even conductors or other components. All we really know is something hot made contact with something flammable. Fortunately no one, including the firefighters, were injured. That’s one big positive, anyway!

Supervstech called it in comment #28, the missed bus bars caused the fire.
 
He bought them in crates this year. Apparently a string of about 40 in series comes out of the crate at something like 3v.. so very very very low voltage in storage. They have never been charged, not once. The project that they were manufactured for was cancelled years ago. I have no idea how they were stored, but it would have been a warehouse somewhere most likely.

When he removes these cells and charges them, 33% or so of the cells behave perfectly, with good capacity and everything seems fine. The other 66% or so have varied results, many of the packs bloating when charging. As you may have surmised, the lot were purchased for very cheap, and are not supported by the company at all.

@plaidcabin , did your friend tell you what the battery chemistry was?
 
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