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Tesla 18650 module disassembly help wanted.

J

joshuahandrich

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Mar 4, 2010
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Would anyone be able to provide some tips and tricks for the disassembly of tesla 444 cell battery module without damaging the cells? I've removed the side panels and slowly peeled back the top and bottom plastic after removing the bus bars. Is there any truck to this or is there any solvent that will soften or dissolve the plastic and/or epoxy without damaging the cells themselves? I know that a solvent or precisely milling the cell holders are the two methods that I have heard of sucussfully freeing them without damage.

I paid less than $600 for the module shipped due to some corrosion near one end from some water ingress but should still be able to salvage the 400 good cells that I need for a 20s20p 5KWHr battery for my moped. I feel this is quite a steal for the cells especially considering they are newer 3.4ah cells with low cycles as they are from a 2016 p90d with less than 300 miles on it.

Once I have freed 400 good cells and receive my nickel strips I plan to spot weld the parallel connections after soldering cooper wire between the nickle strips for the parallel connections for high current handeling.


Any advice or suggestions are greatly appreciated.
 
If you're in the bay I can help you.
 
In Milwaukee, but I appreciate the offer. I've liberated about a quarter of the cells so far. Any tips on a particular solvent or maybe slightly heating the epoxy but staying below like 140 so as not to damage the cells but enough to soften the epoxy? I may also be acquiring another module in the next few weeks. I think methylene chloride or acetone may dissolve or soften the epoxy but I'm not sure what the seperator in the top of the can is made of and how it would react with those solvents. Obviously the cans would be fine especially for a short amount of time, just wouldn't want to risk the insulator. Additionally, once one side is free, it's easy enough to simply pull the cell from the epoxy in the other end without using any tools that may damage the cell, the trick seems to be getting one side out.
 
Can you share photos? I'm not familiar with what glue they used.
 
I'll try to grab some photos showing the glue tomorrow. It is crystal clear and just slightly flexible. I believe that the top and bottom plastic plates are polycarbonate which may be slightly softened and able to be deformed enough to free the cells with ammonia or acetone. Anything that would actually dissolve the plastic is far too hazardous to obtain and use at home as polycarbonate is fairly resistant to most common solvents. I'll probably give acetone a shot on a controlled area at the bottom (negative) of a cell on a q-tip and see if that may ease their extraction.
 
Brake fluid and/or ATF have been known to dissolve some epoxies / potting compounds, if you want to try them on the damaged section of the pack to see if they'll work.
 
I'd probably start with careful application of a heat gun. I doubt solvent would be very practical.
 
I have disassembled 5 modules now. My first attempt was mechanically, and didn't work. I accidentally nicked a cell with a Dremel. I was trying to remove 2 of the 6 series cell blocks to make some short custom modules and gave up do to the catastrophe that happened. I had a fire that lasted for 90 minutes of roman candles, skyrockets and pinwheels. Thinking that water would not help a Li fire, I used LithEx—5gallons of it—to no avail. The cell fires kept propagating to adjacent ones. With hindsight, water would surely have cooled the adjacent cells and stopped the propagation.

My next and final method was to use methylene chloride. It is extremely toxic, used for stripping paint, and kills quite a number of people every year, as well as being carcinogenic. I had a stainless box welded with a 3/4" drain and ball valve. It is 30" x 15" x 6" deep, with at lid with foam weatherstrip to seal. Methylene chloride does not affect teflon, so purchased teflon tubing to go under the ball valve. Also, I'm almost certain that the separator between positive and negative is teflon, as it's unaffected by the MC. I put 1 gallon of MC in the tray after the module was placed in it. Each module was a 5 hour process. Do not go much longer, as I left a module overnight the first time as 4 hours wasn't doing it. The next morning the top and bottom was dissolved away and the cells were falling all over each other and some shorting against one another. Those cells I considered destroyed and discarded, as the place where they short melts the teflon separator. I used a stereo microscope to inspect the separator of every cell. The process is to soak for a few hours until you can peel the aluminum plates off. After more hours you can pull the module out and set it upside down and start removing the polycarbonate. It's a mess. Once one side is off and the other side is soaking in MC, you have to have good timing so as not to allow the cells to be so loose that they fall over and short, but loose enough that you can pull them out and stack them neatly so that they won't short.
If you want immaculate cells as I do, then the hard work begins. You have to peel the MC PC globs off of the cells. The best method I've found is with a steel kitchen scrubbing pad. You have to hold the cells tightly, and don't allow it to short out or you ruin the cell. It's a very long, labor intensive process, and my wife and I have done some lasting damage to our thumb joints from applying the pressure to thousands of cells.
If you use this method. Be sure to use the methylene chloride outside. Use only Viton gloves. Nothing else works for the exposure you need. No filter mask works. You must have fresh air brought in as you have to work over the MC. I used a welding mask with air inlets behind my back and made sure there was a breeze to keep from inhaling MC fumes.
After all this, I was told about someone who simply separated the cells with a chisel. chipping away, but not damaging the cells. It made me wonder if maybe the material had changed, and his module might have been acrylic instant of polycarbonate. If I have it to do over, I might give it a try, but am very skeptical. He told me that it only took 5 hours to separate all 144 cells.
In the future, I think I would buy all new cells, even if they are not up to Tesla standards.
 
Carfull with dichloromethane. Low boiling point means lots of vapors. If you start feeling drunk, go get some fresh air. Also most organic solvent can permeate through gloves... The best is to work under a fume hood.
Epoxy resin is a polymer, and like most polymer, not very soluble in any solvant. Also very resistant to alkali (KOH or NH3 wont help).
Ideally I would try heavy UV-light bombardment of the polymer to break bonds as free radicals, but this would take some time. Once you see the epoxy yellowing, it's already starting to decay and will loosen up easier.

Acid catalysed methanolysis (like 10% H2SO4 in anhydrous MeOH) is probably not very good for the cells themselves. Maybe it could work in milder conditions, but I'm not sure if lithium cells would like it or not.

KMnO4 oxydation and breakdown of resin polymer would also work, but once again, that risk messing up you cells !

Read this : http://www.nilsmalmgren.com/epoxy-chemistry/epoxy-plastics-general-chemical-and-physical-properties/

PS : UV light is carcinogenic for you skin and retina. Protect yourself. You don't want to end up with metastatic melanoma.
 
The module that I disassembled had black epoxy around the cell ends where they were inserted into holes in the clear plastic housing. I used a combination of shallow cuts with a power saw and a hammer and chisel to get the cells out. Each cell then had a collar of brittle black epoxy. Most of the black stuff would chip off with carefull application of a razor knife but the positive end of nearly every cell required sanding with a Dremmel tool to get them clean around the indentation where the can is sealed.
I dented about a dozen cells and punctured a couple but thankfully no fireworks.
Still have two more modules to deal with so I'm subscribing to this thread.
 
Richwordberry sorry to here of your mishap. The smoke is killer. Just to understand the stored potential of batteries and bigger batteries
 
I dont know what glue/epoxy but I have this printer which needed build plate cover replaced and I used turpentine. Limonene is the proper material to use making epoxy like jelly. Worth a try as it is not toxic, made out of oranges. Just a blind guess
 
After looking around it is hard to find some conclusive advise. I got a 18650 tesla module and want to strip it for my bike. Any new ideas or tips? Thanks. Will report back when I tried
 
I Believe that those who have developed effective ways of freeing up the tesla cells, have kept their methods to themselves in an attempt to control the market for recycled Tesla cells .
Also, different modules, (vehicle, model, age , etc)..have different assembly methods and materials.
 
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