So, I've heard that embedding the individual cells in resin(?) leads to far greater stability (can't get runaway fires where one cell lights the next and so forth...). Obviously crap for repairability, but good for safety. Anyone got any good info on this, preferably from the perspective of battery builders?
this post was submitted on 23 Jul 2024
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micromobility - Ebikes, scooters, longboards: Whatever floats your goat, this is micromobility
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This sounds like total BS. I personally designed battery packs for transit vehicles. I would never encase batteries in resin. That would make heat buildup a problem. Although resin filled with boron carbide particles for example would be more conductive than air, it cannot flow. Since the material is not flowing, the heat stays trapped inside the box, only allowed to cool via conduction thru a shitty conductor. On the other hand, air is not a great heat conductor, but you can blow bast amounts of it thru the box. Same for water cooling, except you can't have direct contact between electrical components and water. Thus the best heat transfer system would include air flow. Batteries are generally rolls. This makes the heat generated able to travel faster in the axial direction along the length, than in the radial direction from center to outer surface. Thus cooling the ends of the batteries tends to be efficient enough and may allow you to encase the rest in resin. However from the jelly to the outer case, there is usually poor contact. Only Tesla has come up with a way to transfer that heat more efficiently. But then they haven't really use those cells in production for very long. Normal rolls add conductive strips to connect the collected current to either pole of the cylindrical cell. In Teslas design, the rolled material is offset and has tiny cuts which then allow each electrode to have far better contact. This is both thermally and electrical.
Anyway, don't encase in resin, that's not smart.
Thankyou, kindly. Thought it was BS and the best way to find out is to say it's so, someone will tell you you're wrong, often informatively,. Still, the principle of isolating individual cells from runaway burn seems valid in the case of eBike batteries. If not resin, then what?
Well lifepo4 batteries are less prone to having the dendrite issue where literally metal spikes made of lithium compounds will pierse the separator and catch fire. So switching to this safer chemistry is the way to go.
I dont know how often it happens but I have seen resin encased battery packs catch on fire. Though they were 6 KW/h packs.
I think I heard it called binning which is kind of a confusing term to me because my mind goes to processor fabrication (neerrrrrd)
Last year 18 people died in lithium-ion battery fires, according to the FDNY
And 299 died from traffic violence last year. This year it's 127 Jan-Jun.
Doesn't even include negligence, which is waaaaaay higher