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jbadger
TR#506, MXP, ~3#1206~
Perhaps this means there will be more options when our batteries start dying? It might be possible to replace a sheet or two from salvaged roadsters for a lot less than buying a full refurbished pack from Telsa?
This is huge. The fact that a non-Tesla person can remove, disassemble, re-assemble, and re-install the ESS and still have it work is fantastic news. Among other things, it means the price of a replacement pack will probably be reasonable. It means a higher capacity pack will probably become available even if Tesla never makes one. Given cell supply constraints, Tesla will be in no hurry to put Model S cells in the Roadster ESS.
It comes with a word of caution however. It's dangerous working on the ESS. Electrocution hazard is high and fire hazard is high.
It comes with a word of caution however. It's dangerous working on the ESS. Electrocution hazard is high and fire hazard is high.
Marco2228, did you open up any of the individual bricks? Were the cells wire bonded in there like in the Model S battery? Or were they just squished in there via mechanical force? If they were just squished in there, than it does seem like it would be possible to just throw in 621 new cells to rebuild a brick (assuming the electronics in it still worked). If they're wire bonded in there, than it seems like it would be a lot more difficult to rebuild a brick.
jbadger
TR#506, MXP, ~3#1206~
I would think new firmware would be required if the cells were changed from the original specs. It may not put an even load over the cells causing some to fail before others more rapidly.
Wow, what happened here?
Well, you have to know in which order you have to remove the parts. As I already wrote, I wouldn't take the batterie out and disassemble it just for fun.
Taking the sheets out is an easy task, but it's impossible to remove or even replace a single brick or cell in a sheet. As qwk already said, the cells are glued into the sheet... and electrically connected by a small wire which I think is connected by ultrasonic welding.
@hcsharp: I didn't reinstall it yet, I just connected it with extension wires from the outside of the car to look for the error.
Now I have to tear the car down further to fix the body parts. Unfortunately it's the begin of winter now and the glue needs at least 15 °C for proper hardening. Maybe I should move the chassis into my basement
I am actually thinking of insulating the back wall of the drivers compartment from the outside... still have to figure out, if that's a good idea.
Well, you have to know in which order you have to remove the parts. As I already wrote, I wouldn't take the batterie out and disassemble it just for fun.
Taking the sheets out is an easy task, but it's impossible to remove or even replace a single brick or cell in a sheet. As qwk already said, the cells are glued into the sheet... and electrically connected by a small wire which I think is connected by ultrasonic welding.
@hcsharp: I didn't reinstall it yet, I just connected it with extension wires from the outside of the car to look for the error.
Now I have to tear the car down further to fix the body parts. Unfortunately it's the begin of winter now and the glue needs at least 15 °C for proper hardening. Maybe I should move the chassis into my basement
I am actually thinking of insulating the back wall of the drivers compartment from the outside... still have to figure out, if that's a good idea.
This is truly amazing.
Maybe someone else has ventured this deep into the Tesla battery but I have not heard of it.
Marco, be sure to take lots of notes and pictures. Unless you plan to fix Roadsters for a living, it would be great to have this open source. Tesla has had some of the old Roadster experts move on. A growing company has a lot of promotions and some key managers have sold X Millions in TSLA and are traveling the world, etc. In the far future there will be few to do more than pull and replace.
Maybe someone else has ventured this deep into the Tesla battery but I have not heard of it.
Marco, be sure to take lots of notes and pictures. Unless you plan to fix Roadsters for a living, it would be great to have this open source. Tesla has had some of the old Roadster experts move on. A growing company has a lot of promotions and some key managers have sold X Millions in TSLA and are traveling the world, etc. In the far future there will be few to do more than pull and replace.
You can bet that there have been many packs taken apart. :wink: If you don't know what you are doing, you WILL die! Almost 400V of DC electricity is better left alone.
There are pics of disassembled packs, but Tesla would have a fit if they were posted online(I don't blame them), so it's just better to leave it be.
I'm sorry but I seriously doubt many (if any) packs have been taken apart by non-Tesla employees. First, it's well known that it's dangerous. Second, nobody wants to void their warranty. And nobody knew for sure that they could put it back together without expensive damage. I know hackers like to hack, but they don't do it with $40k parts when risks are so high. I'm disappointed to find out that the individual cells are glued into the bricks. I've always wondered how they kept that seal from leaking.
@jeremyz, You're confusing bricks with sheets. There are 9 bricks in a sheet. But you got the cell count right per sheet. Each brick is surrounded by metal so a fire will not spread uncontrolled to the whole pack.
wiztecy
Active Member
Question will be how to rebuild these packs once they're toast. Also the ability to measure each sheet down to each brick so they can be rebuilt cost effectively. So with all the cells locked down into each sheet it sounds like you can only salvage good individual bricks. With the new brick that needs to be built it has to be seen if they still need to be epoxied back in or if possible layed back in for easier maintenance in the future. I think the next step would be for people to start contacting battery / refurbishment companies. For example my friend sent his 1st Gen Rav 4 EV's pack out to Sacramento where they rebuilt it with refurbished NiCads.
Also in the case of a bricked Roadster pack, talking with people, it is possible to recover the cells and bring them back to life from the bricked state although there may be some cells/bricks that might not recover. But there appears to be hope.
wiztecy
Active Member
Whats your best guess on how they swap cells? I'm guessing they just salvage usable bricks and stick those bricks to make up a sheet with similar CAC values to match the other sheets. Then toss / recycle the materials of the old brick. However someone could build a new brick and epoxy all the cells in as Tesla did. The advancement / trick would be skip that step with the right engineering principles. The reason to epoxy the cells I presume is to keep the cells from moving/shaking/damaging each other?
Yes, I would say that they do exactly that. Back when they assembled the original packs in Palo Alto, they had a special setup to measure, and assemble the bricks with cells that were as closely matched as possible.
I wouldn't do that. If a cell has been deeply discharged and you bring it back to life with some special charging technique, small, sharp materials (e.g. copper) can dissolve out of their usual place. If you then keep using the cell these materials can damage the separator and cause an internal short in that cell, which in turn can cause fire.
Well, I don't know cells from the chemical point of view and don't know how high the possibilities are, that the cells would actually fail, but I wouldn't take that risk and with 6831 recovered cells in a car, I simply won't feel good.
Yeah, cell matching is critical. It would take a lot of work to develop all the tools that would be needed. Not to mention figuring out how to test the various circuit boards and other components in there, of which we know nothing. I'm starting to appreciate why it costs 40k to trade.
Good to know - I always assumed that if you could get them back up to 2.5v without catching fire that they would then be OK after that. I've recovered a few Li-Ion cells that were over-discharged and they all worked fine for a couple years after. I don't know the chances of forming sharp dendrites near the separator but what if it's more than 1 in 6831 like you said.