Pics/Info: Inside the battery pack

[cgiGuy]

I know these may be more valuable as good cells, but if you find a way to get them apart, I'd be willing to buy one just to use as a demo for people who ask about the battery. Bet a lot of others would, as well. I wish Tesla would give us a "keychain" with a fake battery on it with the car.

 

[Pollux]

I carry around a couple of 18650s that I often show people when they are looking at the car. I ordered them off of Amazon from somewhere in China. Yes, not identical to what's in the battery pack. But close enough for most people.

Having said that, if @wk57 goes into the "ship a few cells for customer demos" arena, then sign me up!

I know these may be more valuable as good cells, but if you find a way to get them apart, I'd be willing to buy one just to use as a demo for people who ask about the battery. Bet a lot of others would, as well. I wish Tesla would give us a "keychain" with a fake battery on it with the car.

 

[hcsharp]

How did the punctured cells behave? Did they start smoking and/or catch fire like a laptop cell would? I wouldn't store those in your house.

So it sounds like this module is different from the previous packs that you got WRT the glue? Why do you have to separate the cells from the modules? Can't you just keep each module intact like you did with the previous packs? Thx for sharing your adventures with us!

So, I have a module from a 3rd pack that is damaged and I decided to dismantle it to harvest the good cells. Honestly, I don't know what I've gotten myself into. My original assessment of the pack being built like a tank definitely applies.

Each cell is individually glued to the hard plastic framework that holds everything in place. This framework is glued to the aluminum rails on the sides. I butchered the rails off of the thing in hopes to be able to maybe torque the whole thing apart. No dice. I literally jumped up and down on it while having one end propped up and it was solid as concrete.

I managed to remove about 6 cells without damaging them through brute force efforts on the plastic on the edge row of cells, and 3 others I punctured in the process. I think the only way to safely remove them would be to somehow dissolve the glue, unless I'm missing something.

Oh well.

 

[wk057]

How did the punctured cells behave? Did they start smoking and/or catch fire like a laptop cell would? I wouldn't store those in your house.

So it sounds like this module is different from the previous packs that you got WRT the glue? Why do you have to separate the cells from the modules? Can't you just keep each module intact like you did with the previous packs? Thx for sharing your adventures with us!

The punctured cells actually still work fine, surprisingly. Nothing catastrophic. I put them on charge out in the yard, just to see what would happen... and nothing. They charged normally.

This module is from a 3rd pack that I received 6 modules from. This particular one was damaged and not usable in my setup, so, I'm dismantling it.... for science!



As for demo cells... I'm not sure I'd feel comfortable with having these sit around destined to discharge. Without being used, eventually the voltage will drop to the point where it is unsafe, even if you insulate it and all. I wouldn't keep a loose one in my glove box, that's for sure.

 

[Johan]

Did you try to read the QR code on the cells? Would be interested to know what it says. Maybe it's a link to a secret data sheet? (one can dream right?).

Anyway I'm on a SurfacePro pad here and don't have and good image manipulating software installed so not able to process it well. Someone wanna try?

 

[wk057]

Did you try to read the QR code on the cells? Would be interested to know what it says. Maybe it's a link to a secret data sheet? (one can dream right?).

Anyway I'm on a SurfacePro pad here and don't have and good image manipulating software installed so not able to process it well. Someone wanna try?

View attachment 76182

I actually did a while back... seems to just be a serial number. Nothing useful.

Edit: Here is my post earlier:

I was able to decode the tiny little data matrix on the one cell I snapped a shot of: 5221DACP0143000B

I assume its a serial number for the individual cell?

View attachment 59051

I actually reconstructed the barcode by hand for that one, since it was impossible to get a good pic.

 

[Johan]

Impressive.

You've got an eye for detail

 

[wk057]

so yeah... about that damaged module I was liberating cells from... done with that.

Somehow one shorted out while I was removing glue/plastic. Immediately went red hot, popped, flew off like a firework and of course, directly up into an open door to my basement ~15' away. (I was working on this outside by the pool, which is 3 steps down from the basement door and ~15' away.) Slid across the tile floor and landed in front of my fiance's PC another 25' away. Sat there for several seconds while I was chasing after it with a fire extinguisher in hand. Hit it a few times with the ABC chemical, and the chemical boiled on the shell. Seemed to cool is a bit, though, so hit it a few more times, grabbed it with a pair of pliers and leather gloves and threw it back outside in the dirt..... along with the entire rest of the module and the rest of the cells I removed previously.

So, think I'm done with that project.

 

[patrick42h]

That's a little scary. I'm glad you're fine and no major harm was done. I guess this is just a reminder that if these cells store enough energy to move a 5-ton car around, they can be tricky if they get damaged.

 

[JRP3]

Ouch, a little more exciting than you were expecting. :scared:

 

[lolachampcar]

wk,
you crack me up..... like a kid in a candy store. I only wish I was there next to you prying away

 

[jerry33]

That description reminds me of one kind fireworks we had when I was a kid. The kind with the 40x2 mm metal "wings" on the side. I see they now have plastic wings.

 

[purplewalt]

so yeah... about that damaged module I was liberating cells from... done with that.

Somehow one shorted out while I was removing glue/plastic. Immediately went red hot, popped, flew off like a firework and of course, directly up into an open door to my basement ~15' away.

So, think I'm done with that project.

I have been following this thread with interest for quite some time.
You have a lot more patience and tolerance than I would ever be able to muster.

Might be best to quit while you are still ahead (and in one piece).

 

[wk057]

wk,
you crack me up..... like a kid in a candy store. I only wish I was there next to you prying away

Definitely was having fun up until the rocket cell. lol.

And honestly, if it didn't fly inside the house (ie: if I didn't leave the door open) it probably would have been a little exciting instead of dangerous. lol. I figured if one went nuclear I would be able to just get it on the ground and hit it with the fire extinguisher and/or garden hose. I didn't expect it to literally take off like a rocket and fly that far all the way into the house :-\

Edit: Cleanup of the aftermath complete. Total permanent damage: None.

I have been following this thread with interest for quite some time.
You have a lot more patience and tolerance than I would ever be able to muster.

Might be best to quit while you are still ahead (and in one piece).

Well, this was a somewhat expected event. If you short the cell with no protection, it's going to go up in flames, no doubt about it. In this case my forensic analysis leads to me to conclude that I had accidentally hit the edge of the positive end and bent the negative casing into it. There was no stopping it after that. In hindsight the hit that caused that damage was probably almost a minute prior to what I initially thought caused the short, so the battery rocket didn't happen instantly like I had originally thought.

That said, I think the production setup I have in place is much safer. Cell level fuses are in place to prevent these types of shorts. Climate controlled area. BMS, fire protective measures, etc.

 

[kennybobby]

There is always interesting experiments in your lab...Don't stop the research.

So do you think maybe 73 cells were shorted thru the case of one cell? How many amps?

 

[wk057]

There is always interesting experiments in your lab...Don't stop the research.

So do you think maybe 73 cells were shorted thru the case of one cell? How many amps?

I had removed the bus plates prior to this, so, it was only one cell at ~50% SoC. But looking at whats left of it (finally cooled off after a couple hours), I can see where the negative casing was shorted to the positive tip plate where the insulating ring there was smashed by my accidental whack on it. So it would have been a pretty high current direct short. Even if it were only the same amount of power the P85D uses at full power, that's still something like 18A.

 

[Danal]

As for demo cells... I'm not sure I'd feel comfortable with having these sit around destined to discharge. Without being used, eventually the voltage will drop to the point where it is unsafe, even if you insulate it and all. I wouldn't keep a loose one in my glove box, that's for sure.

I've tried to get bad behavior from fully discharged "bag" style LiPo cells (below about 2V) every way I can: I've shorted them, cut them, driven conductive things through them (nails, screwdrivers), shot them (with a .22), tossed them in big fires... and I couldn't get any hazardous behaviors.

As you discovered, charged cells are an entirely different matter.

But a "Demo" cell? Discharge it, then clamp copper braid around it with a "C" clamp for a couple of days. After that, its not going anywhere from its own energy.

 

[bxr140]

I think the only way to safely remove them would be to somehow dissolve the glue, unless I'm missing something.

If you haven't given up and you haven't already done so, use a hot knife to cut away the fillet and any other exposed epoxy. Then, as suggested already, use a heat gun to soften up the bondline. As soon as you get close to the transition temp you should be able to pop the bondline by twisting or prying the cell, or otherwise using whatever leverage is geometrically possible. (Twisting is usually the best)

Ideally you should keep direct heat off the cells, up to and including shielding the cells with a hunk of metal or something more exotic (if you have the means), like high temp blanketing or something. If you can heat from the backside that's even better.

I have no idea how hot is too hot for the cells, but you can tape a thermocouple to the cell on the part most exposed or closest to your heat source.

 

[wk057]

If you haven't given up and you haven't already done so, use a hot knife to cut away the fillet and any other exposed epoxy. Then, as suggested already, use a heat gun to soften up the bondline. As soon as you get close to the transition temp you should be able to pop the bondline by twisting or prying the cell, or otherwise using whatever leverage is geometrically possible. (Twisting is usually the best)

Ideally you should keep direct heat off the cells, up to and including shielding the cells with a hunk of metal or something more exotic (if you have the means), like high temp blanketing or something. If you can heat from the backside that's even better.

I have no idea how hot is too hot for the cells, but you can tape a thermocouple to the cell on the part most exposed or closest to your heat source.

I thought about this, and I took a piece of the framework that I had broken off to my heat gun to see what it would take to loosen it. The glue or whatever it was wouldn't melt. The plastic housing was burning and the glue was still solid. :-\

Plus, heat + these cells scares me a bit at this point. Data I've read suggests thermal issues possible beyond 150F.

 

[bxr140]

I thought about this, and I took a piece of the framework that I had broken off to my heat gun to see what it would take to loosen it. The glue or whatever it was wouldn't melt. The plastic housing was burning and the glue was still solid. :-\

Plus, heat + these cells scares me a bit at this point. Data I've read suggests thermal issues possible beyond 150F.

It won't melt, but it doesn't need to. It just needs to soften enough to the point where you can pop the bondline. Where I work (we build satellites) we have to debond expoxied things all the time. Its all about being patient and controlling the heat. Not everyone has the right touch, but based on the practical/hands on competency shown in your threads, I suspect you won't have any problem keeping it under control.