I spent some time this evening cutting into the case. The seam where the two halves were fused together has to be by far the thickest part, but I still think it is the safest place to cut it open. Just for kicks, I tried to hit it with a few different types of blades first. Don’t even bother. This thing is pretty dang stout.
My dremel adapter is working really well to precisely hit exactly where I want, but I am getting some melting when I get too aggressive. As I get deeper it is hard to stay in the sweet spot, without stalling the motor or melting the plastic. Regardless, I think I may get a clean enough cut that there is a chance I could re-use the case.
I can’t find a dremel cutting wheel that works well, but I at least found one type that is effective without gumming up too badly. The problem is that they wear down pretty quickly and I have already shrunk 6 of them down to nothing. I might end up going through 20 before this is over.
A coping saw works pretty well on some of the corners. The inside of the handle is going to be the hardest part by far. I can safely say getting to these cells is going to take longer and much more effort than welding together a whole new pack of 18650 cans of the same quantity.
Vasco Velez here in Australia helped a friend cut a Lift battery open and Vasco told me that epoxy is poured in between each battery so you can’t get them out. I have two dead Lift batteries that were replaced under warranty.
As far as I know, Lift is using Polyamide 66 reinforced with glass fiber as battery case material which has a melting point >230°C. Best in class material for this kind of application where the cells and BMS can catch fire.
I would first try to heat the glued parts (sides) with a heat gun up to 150°C to melt the glue. It should be doable this way because I highly doubt they would use a high temperature epoxy as bonding glue (usually more $$ than conventional ~100°C resistant epoxies). The cells should still be fine as they are also protected by a second structure and not touching the sides directly.
Make sure to wear gloves as everything will be pretty hot and goggles too, safety first !
Might be indeed, that’s at least what we see in the video. The purpose of the operation here is however something else (at least for me). We are trying to openly share the specs of the components inside to help the diy community with the choice of BMS / cells or other components for this application.
I feel like my Onean pack is also full of epoxy but we’ll discover this pretty soon too ! Again, what might be interesting is the BMS they use (Onean is 12S16P, to technically up to 160A continuous) and what’s inside too, there are very few informations on this topic out here…
Exactly. Even if there is nothing salvageable, I am interested to see what is inside this 3,500 pack and why it stopped working.
I am resisting the urge to bring out the heavier saws like my large oscillating tool, @noahark. It may come to that today and I might be able to get a fairly clean cut once I get the groove deep enough to guide it.
I don’t think it is epoxied or glued together anymore. They may be using some sort of plastic welding process that fuses the two pieces together by heat. The seam is very tight and material is consistent. A MUCH better job than the multiple flyproducts gas tanks that split at the seams on my paramotor!
After sleeping on it, I realize that I need to just cut across the top of the case shy of the handle. I do not want to spend the time it will take to carefully cut around the inside of it and would probably butcher it if I tried.
The dremel adapter I printed to precisely control the y and z planes for the cut:
Do you think you can then share a pic of the sealed surface to find out how they did ? Would be interesting to compare this method to other batteries as wel.
I don’t have that exact wheel, but the similar ones that I do have for plastic and wood gummed up and just became a spinning plastic wheel. It is a tough call between the search for a better cutting wheel and waiting a day or two for Amazon, or spending the hour of going to the store and hoping the have what I need, or just staying the course with what I have that is mostly working (albeit slowly) and finishing it in as much time. I think the best tool for the job would be the oscillating tool with a plastic/wood bit since it will probably not get fouled up due to the lower speed, but I will not be able to keep the same clean cut line. I may just give it a shot and see. I know everyone is eager to see what’s under the hood.
I had to step out for something else and stopped by the hardware store today. They have every other wheel under the sun (including all the ones I have tried already) except for that one, Jezza! Doh. Probably should just finish with what I have.
I don’t see that is a viable option with this material. It would release some incredibly noxious fumes, be messy, and have a higher danger factor with the batteries and wires in such close proximity.
Mine only has 1 speed and it melts the plastic and junks up the blades just like the dremel, but I am close now. I just need to (VERY carefully) do the cut across the top.
The real Fein tool is what I have. Expensive, but worthy every penny and I use it every day. The diamond blade better for that type of work, but standard blade should do fine.
It’s open. Here are some quick shots. I am checking things with my multimeter now. I did hit a small orange wire when I cut across top and lost patience, haha.
SCORE! All the cells are good. It is an interesting configuration, but all the channels are balanced within .01v of each other. The cells are resting at roughly 3.24v. This is quite a fancy BMS. There isn’t much room to get to it due to my choice in cutting across the top. I am not sure yet if I would cut it the same way again or not next time.
