New York City wants lithium-ion e-bike batteries to be stopped at the border when they don’t meet national safety standards after rash of deadly fires::After a series of deadly fires.
Sub-standard “spicy pillows” need to be banned. The amount of energy and that fact that water or any normal ABC extinguisher cant put the fire out is enough for me to get really strict on regulating them. Especially in apartment/condos
What in the world is a “spicy pillow”?
a puffed-up lithium cell that’s about to explode. soft, squishy, and very flammable!
Bike shop worker here: not only are the direct to consumer Asian eBikes shoddily built pieces of shit with proprietary parts galore, but we refuse to intake non mainstream brands’ eBikes for this reason. Worst shit
Yeah I have the feeling a lot of them are as bad or in some cases worse than bicycles upfitted with gas engines.
Reminds me of what the hoverboard craze of the mid-10s resulted in, products with a bunch of shoddily-assembled components that turn the batteries into bombs making it onto store shelves faster than the new thing powered by said batteries can get new safety guidelines released for it
Imagine reading this in the 80s - we would have thought that Back to the Future was prophetic.
As someone who designs global battery powered products in the USA and is well versed in the regulatory hurdles, enforcing these rules is long overdue. The fact that people willingly buy and bring these illegitimate products into their home and wear them on their body is mind blowing to me. You can design a safe lithium products but doing it requires full knowledge of the chemistry, electrical design, safety certification process and some wisdom. Chinese vendors on Amazon have very little of this.
I do this on the side, buy bulk low cycle lithium ion cells, spot weld them together into banks, and make larger packs.
What is the biggest safety problem seen with these?
My packs are 64P, right now 4s but hopefully 7s soon.
My main safety features are per-cell 5A fuses, 100A fuse on each bank under the battery wrap (not removable without cutting the wrap), and keeping the cells and nickel strips under a layer of kapton tape, followed by an ABS plate I designed and printed, then all the wiring, taped to the ABS with kapton tape. Which is then inside of the battery wrap. I use a lower current circuit breaker on the whole circuit.
My layman research suggests that loose wires are the main reason for fires, so all wires are taped down, and the nickel strips are protected from stress. A cell shorting out should blow the 5A fuse. And if I’m careless and bump the two terminals to a conductor while moving it, there’s always a 100A limit. I also only use low-cycled matched cells and currently am charging to 4V and discharging to 3V.
Any other things I can do to make it safer?
Whoa, there is a LOT to unpack here so I will do my best. Please understand as I’m an engineer by training I will always advocate towards caution rather than YOLO so I’m going to spell out a lot of doom and gloom so read at your own peril. I’m not trying to poop on your hobby/business.
Inquiries; What kind of cells, 18650s? What brand cells do you buy and do you know their use history? Do you mix model numbers? I assume these are bare cells with no protection circuitry and you add the 5A fuse? What kind of fuse, a PPTC? And is that a typo, 64 in PARALLEL? 4S64P? That is bonkers, what the heck are you doing with them that requires that kind of amperage?
OK OK, so, do you use a BMS? How are you handling these packs other than the fuse? You NEED a BMS to at least balance the 4 series strings and monitor the packs temperature and shut it down if any part of the pack gets too hot. Lithium cells have a very narrow range where charging is allowed and a slightly wider range where discharge is allowed but at some point you need to turn it off. In terms of massively paralleling the batteries this is dangerous territory unless you are acutely aware of the cells, their limits, age and tight monitoring to notice when a handful of the cells are aging (getting higher ESR and forcing the others to handle the increased current which might exceed their safety limits). The end goal is to balance the current evenly between the cells in parallel and its not trivial, if you force all the current through a handful of cells you will ignite a lithium fire.
Regarding charging to 4V and discharging to 3V, most modern 18650 cells from good vendors charge up to 4.2V with a float charge so you’re leaving charge behind but 3V seems way too low. I guess it depends on how long you want the pack to last. There is max and min voltages the cell vendor will recommend but then if you ask they can give you plots of the cycle life at different depths of discharge and typically in my world we don’t go much lower than 3.2V to ensure the packs last well past 500 cycles. The deeper you discharge the more stress you put on the cathode.
Finally, loose wires are certainly a cause for fires and since you’re hand making these its likely your biggest risk but in addition to that dendrite growth in the cells. If you abuse the battery either with temperature, over current/current imbalance you slowly introduce dendrites which keeps increasing the chance the cell will catastrophically fail with continued cycling. Its statistics and with the number of batteries you’re playing with any little bit of abuse will grossly magnify the chance of a big failure to happen. Cells can and do spontaneously fail from internal damage but its a lot more likely to happen during charging.
In summary, you are playing with some serious power levels here, I would read up some more before you get much further. Especially before you step up to 26V! I hope this helps!
Cell quality is important. You want to be using known good quality cells like those from Panasonic, Samsung, LG, etc…
How you manage temperature, charge and discharge is also really important, dendrite growth can cause cell failure in time. Charge temperature is extremely important. So you want to make sure you’re using a smart programmable BMS where you can set up all the protections properly. Ideally one with as many temperature probes as you can find, 4 is good, 8 is better and some will have that many.
Otherwise making sure nothing can short out internally is important too, but it sounds like you’re putting some thought into that. Most critical IMO from what I’ve seen on pre-made battery packs is making sure your series banks are well insulated from each other and have no chance of vibration causing the cells to wear through their heatshrink and touch each other.
We really need a better battery technology, one that doesn’t trivially become an incendiary device.
From 1980 to 2018 they say vehicle fires decreased by 60%.
That is done by regulation and holding companies accountable for their products. The issues arise from low cost products from shit companies.
People hate inconveniences like regulations because they make prices higher, but security is never about convenience.
We need to stop fining companies miscule amounts and ban imports from companies that don’t meet stricter regulations. It isn’t going to cost $5 dollars for junk you throw away after one time use if we do that. Users will pay more for a higher quality reusable product under those regulations as well.
Safter and less e-waste.
I mean shit, why are 1 time use disposable electronics even allowed? E-cigarettes you toss instead of swapping a cartridge are a quick one that comes to mind. Apparently people get mail/advertisements in the mail now that have some sort of lcd screen so they can play a video. So you just chuck a battery and screen when you open your mail. That’s disgusting. (Amazing how far the tech has come, but still)It seems to me that one simple (and therefore probably wrong) solution to e-waste would be to have retailers, distributors, and manufacturers accept nonworking or obsolete devices for responsible disposal or recycling.
Turn the one-way supply chain bidirectional. If you sell it, you’ve gotta take it back when it’s broken. If you have an assembly line for making it, you can make a disassembly line for taking it apart. If that’s expensive, well, apply some ingenuity to making it cheaper.
Want to deal with fewer broken devices? Make devices that don’t break so much.
There has actually been a ton of progress with this over the last decade.
However, everything we have discovered so far either can’t hold as much energy, has really limited charge cycles, or is far too expensive to use at scale.
Ton of progress?
I would refer to that as “research ongoing but no progress yet”.
Current 18650/21700 Li-ion cells are a lot safer than they were 10+ years ago, less chance of thermal runaway and fires now.
Is this an American thing? In Europe we have regulated batteries and chargers made by well known companies like LG, Samsung and Panasonic.
You can find these in the US but they’re a lot more expensive so folks always save the 50% to buy the no brand trash that breaks in a month to one year and is also a chemical bomb.
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