LIFEPO4 Smoke and Fire Dept

[jhooligan65]

Thought this would be good to share. Ive been adding solar and building battery banks for the past year. I am a commercial electrician but the battery building is new territory. I has this 310AH 16s battery operating just fine with an Ant BMS. Luckily had it in a metal box and in the garage. Ive had no issues, solar charges during the day, battery at night. I cycle pretty low (I think) I stop charging at 54V and Start back up at 51.2V. The inverter was still operating while she was smoking. I dindt have a temp sensor on this specific cell, so it just cooked. I can not for sure identify what caused it. Im hoping to blame myself as I would like to use the other 15 cells. But concerned it was an internal cell failure. Has anyone experienced this?

 

[400bird]

Sorry to hear and see that.

I see the insulation between the cells. Do you have any electrical insulation between the cells and box?

 

[jhooligan65]

I did but it melted. It was just foam. Do you think the cell could short out on the metal case? I would think the metal case would need to be bonded to something to do that.

 

[400bird]

It seems like the most likely cause, lacking other ideas.

The metal cell cases are connected to one of the battery terminals. If you had a couple nicks in the blue shrink wrap, you can pass current and create heat.

 

[crossy]

I see the insulation between the cells. Do you have any electrical insulation between the cells and box?

Yeah, that was my immediate thought too.

 

[jhooligan65]

It seems like the most likely cause, lacking other ideas.

The metal cell cases are connected to one of the battery terminals. If you had a couple nicks in the blue shrink wrap, you can pass current and create heat.

Im racking my brain. Was/are they bad cells? Was my terminal/Bus Bar not torqued correctly ? Could that make enogh heat to get it going? Why didnt my BMS shut it down? (It does when I dont want it to!) lol... Are the othe 15 cells safe to use?

 

[SparkyJJO]

How hot was it? I'd wonder about thermal damage to the immediately adjacent cells. But if all looks good I'd keep the others going.

 

[jhooligan65]

How hot was it? I'd wonder about thermal damage to the immediately adjacent cells. But if all looks good I'd keep the others going.

The case was over 200 degrees F. the cell above it was a little melted. possibly swollen. They all check out. my BMS read around 3.3V on all cells. Even the cooked one ws 3.2V. After removing them all and checking with a meter the range is 3.27 to 3.31 per cell. resistance is between 2 and 4 megaohms. The cooked one is 6 megaphms and still has a voltage of 3.17v.

 

[jhooligan65]

The case was over 200 degrees F. the cell above it was a little melted. possibly swollen. They all check out. my BMS read around 3.3V on all cells. Even the cooked one ws 3.2V. After removing them all and checking with a meter the range is 3.27 to 3.31 per cell. resistance is between 2 and 4 megaohms. The cooked one is 6 megaphms and still has a voltage of 3.17v.

 

[SparkyJJO]

I'm no pro, but I'd use it while keeping a stink eye on it for a while.

Could either replace the burnt cell or reconfig to 15s, I suppose.

 

[jhooligan65]

Im thinking 15S. Unless the seller will warranty it. I just got them in May. I have 2 other set ups been running for a year with no issues. Wife wasnt too excited about the smoke show!

 

[Bob B]

It doesn't look like the heat was generated by the bus bar connections. The terminals still look OK.
Doesn't seem like it should have shorted to the case if there was foam and the plastic wrap on the cell ..... not knowing what caused it is worse than making a mistake and causing it.

Edit .... after looking at that cell again, it does look like the top of the cell got pretty hot .... could have been a connection.

 

[jhooligan65]

It doesn't look like the heat was generated by the bus bar connections. The terminals still look OK.
Doesn't seem like it should have shorted to the case if there was foam and the plastic wrap on the cell ..... not knowing what caused it is worse than making a mistake and causing it.

I can not agree more. I want to find out it was something I did so I dont do it again!

 

[Bob B]

I can not agree more. I want to find out it was something I did so I dont do it again!

Just FYI ... I edited my post about the time you posted.

 

[jhooligan65]

Just FYI ... I edited my post about the time you posted.

 

[jhooligan65]

Not sure which post you are referring to.

 

[Bob B]

I edited post 12 about the same time you replied to it.

 

[jhooligan65]

I edited post 12 about the same time you replied to it.

Aahhh. Got ya. I do agree. The post looks Hot. I examined the bus bar. looks good, but , the post looks toast! On a reddit forum someone commented maybe because I stacked them sideways? maybe the weight bent the aluminum case?

 

[Bob B]

Aahhh. Got ya. I do agree. The post looks Hot. I examined the bus bar. looks good, but , the post looks toast! On a reddit forum someone commented maybe because I stacked them sideways? maybe the weight bent the aluminum case?

I don't like putting them on the side I don't know what the spec is for how much you can stack them on their side ..... I would much rather each row had it's own shelf.

 

[jhooligan65]

I don't like putting them on the side I don't know what the spec is for how much you can stack them on their side ..... I would much rather each row had it's own shelf.

Im going to look into a new configuration with a 15S maybe. Try to eliminate any "what ifs"

 

[Daddy Tanuki]

It doesn't look like the heat was generated by the bus bar connections. The terminals still look OK.
Doesn't seem like it should have shorted to the case if there was foam and the plastic wrap on the cell ..... not knowing what caused it is worse than making a mistake and causing it.

Edit .... after looking at that cell again, it does look like the top of the cell got pretty hot .... could have been a connection.

I have wondered on more that one occasion about the wisdom of brazing a stainless steel stud to an aluminum pad...(and no those posts are not welded, you cannot weld stainless and or any ferrous metal with aluminum in a true weld, best you can get is a brazed/soldered etc. joint)

 

[SparkyJJO]

Yes that one terminal looks hot, but it looks like the primary damage to the cell was the bottom.

 

[Zwy]

This photo shows there is some serious heat at the terminal, the plastic melted around the terminal. The terminal has also moved from it's original location on the busbar, you can see the witness mark on the busbar from it was originally installed. Note the discoloration of the busbar, some serious current had passed thru it. My honest opinion is the terminal had become loose causing the failure. I'm not sold on the multilayer busbars, at some point the layers move relative to one another and the result is loosening of the terminal. Stacked tolerance is that when assembling anything of multiple layers, there is a tolerance because materials differ in thickness on each layer. I prefer a single solid busbar with compression to eliminate any movement. Stacking will never end up perfect simply to to the busbar material having imperfections from when it was originally manufactured.

 

[x4dow]

1 terminal badly tighten can get really really hot. its the only possibility i can think off. I had batteries i finished building and then run 100A+ through them, and then feel the busbars, if 1 of them is clearly warmer , is usually a connection there that isnt 100% tighten.

 

[cs1234]

This situation sounds like it might have been preventable by checking with a FLIR style temperature scanner. Could have checked for hot spots during operation after building and periodically thereafter. Might be worth getting one, like @Will Prowse said in one of his videos recently.