Is it so fucking hard for chinks NOT TO install shitty BMS that don't balance cells? It is just idk, 0.1 US dolla difference?Also, why did they even lie? It says 10 AH on the battery heatshrink, while in reality it is 7.8 AH. That $0.1 saved resulted in 4.22 - 3.85 V disbalance in cells. No fucking wonder it did only like 12 km.
>>1949696>18650sYou are a braver anon than I. Despite knowing quite a bit about battery safety and ohm's law and all that shit those battery packs with the 18650s and 20700 scare the absolute fuck out of me. I know with one battery once shit goes south it goes FAST but having a bunch of them together, fuck that.
>>1949697>Despite knowing quite a bit about battery safety and ohm's law and all that shit those battery packs with the 18650s and 20700 scare the absolute fuck out of me.They do scare the shit out of me too. Especially high discharge cells, when you short them, they get so hot copper and aluminium catch fire. These cells (SINC 18650) aren't high discharge, but they still can make you shit your pants in case.So whenever I work on cells, I want to have them discharged to lowest practical level. Not in this case since I'm trying to understand wtf is going on with balancing. But yes, battery stuff is scary, and I think I should mention that untrained people shouldn't screw around with internals of the battery at all. Other thing is that fire extinguishers are kinda useless with lithium battery fire, and in case of fire, best thing you can do is just throw it outside in safe place and just wait for it to burn.
>>1949697Just build a powerwallhttps://hackaday.com/2016/09/29/homebrew-powerwall-sitting-at-20kwh/
>>1949696I want to open mine now. Where do I get a new blue shrink wrap that size?
>>1949727>I want to open mine nowI will warn again, it might catch fire if you aren't careful.Before you open, figure out what is the purpose of BMS, balancing circuit, etc. > Where do I get a new blue shrink wrap that size?Cheapest option would be aliexpress. Get the PVC wrap, as not only it is cheaper, but silicone actually sticks to it, which allows you to waterproof the battery. You can also get heatshrink at industrial electric shop, but its much more expensive as that wrap is meant to withstand like 1kV or so. You can also use soda bottle, but there is a good chance to cook the battery from excessive heat. Since I don't really care about shit looking stock, I will just tape it back using electrical tape. But if I were to do it for somebody else, I'd buy proper wrap.
>>1949700>>1949697They're fine if you know what you're doing. A good tip is to have a 5 gallon bucket of sand nearby. If you cover it before it gets out of control you can keep it contained.>>1949696One more issue is these fucking chinks rarely use is thermistors for temperature protection. The most common reason they catch fire is because of thermal run away. Once lithium cells pass a certain temperature (primarily from sustained high loads) they keep going and there's no way to stop it.Idiots talk about banning e-bike batteries, battery registry's, etc. when batteries are safe when made properly. The issue is the battery manufactures.
>>1949744>One more issue is these fucking chinks rarely use is thermistors for temperature protection.That's true. But I don't think thermistor is of any use, given discharge/charge currents are reasonable.I think only e-scooter that do have thermistors are ones from NIU and Ninebot.Btw, I think you can easily add a thermal cut off feature to any BMS, just by connecting several balance wires via a thermal fuse, 50C one maybe. Because if battery got to 50C, there is something wrong with it>The most common reason they catch fire is because of thermal run away.Which is caused by mechanical damage (a lot of batteries just rely on the heatshrink to prevent internal shorts, which wears off due vibrations and shorts to the chassis, bypassing all your BMS circuits) or total lack of fuses. >Idiots talk about banning e-bike batteries, battery registry's, etc. when batteries are safe when made properly. The issue is the battery manufactures.Issue isn't even manufacturers, its china/importer problem really. Importer asks for an e-scooter, china dude tells him it is $400, importer asks for $300 and china dude tells fine ok, and then they cut corner everywhere they can. Like in my case. How much more would a BMS with balancing cost? 10 cents? And you know, it is not a fire hazard, it just means that all these e-scooters will end up in e-waste pile somewhere, just because battery is dying earlier than it should. Lithium batteries in laptops, where they are closely matched and have proper BMS, they last for 5 years, with some capacity loss, maybe even decades. Good for me as now I can search FB marketplace for these scooters with utterly useless battery and resell them, but sucks for everyone else with foreskin intact and normal nose.
>>1949760Whether it's a thermistor or thermal fuse, something should be included.It's a series of issues. A lot of these shitty ebike/scooter/skateboard/onewheels rely on everything being perfect and shit themselves when things go wrong.They expect the charger to manage everything regarding safe charging or they make the charger dumb and expect the BMS to handle everything. If the charger fails and supplies too much current, the BMS isn't designed to fail safely in that scenario so it sends that excess current to the batteries or the solder traces overheat and fuse together causing a short. The BMS doesn't have good short circuit detection and relies on the solder joints never failing. The wires are undersized and they count on the consumer never overloading them for too long for it to become an issue. At best the consumer wastes time/money fixing it or deals with premature aging. At worse it starts a fire. All of which could have been avoided with proper engineering.I didn't think of the importer thing. That probably plays a role, but you see the same thing from batteries sold direct from the manufacturer or on major stores like eBay or Amazon.Lol, one man's trash...Sorry for the incoherent post, I'm phone posting.
>>1949762>Whether it's a thermistor or thermal fuse, something should be included.Yes, but I think it is one of the least important safety features. I'd prioritize fuses (insane, but I've no idea why do they all skip fuses, given they are really low cost), and proper mechanical design (spacers/insulation between cells, fiberglass or thick plastic to prevent shorts to chassis, etc).>It's a series of issues. Pretty much. I think "safety cheese" model applies to batteries too.The saddest part is that all technologies to make batteries safe existed for years. In laptops, for example... But in PEVs shits always lacking. Maybe because PEVs were designed out of RC model parts back in the day. Like 2012 or when did first e-scooters appear, they all used shittiest LiPos with shittiest BMSes imaginable. Very few batteries survived to this day, while scooters themselves are still fine.>A lot of these shitty ebike/scooter/skateboard/onewheels rely on everything being perfect and shit themselves when things go wrong.They don't rely on anything, except profit and money. Ninebot, for example, they actually have made pretty good batteries, safety-wise... But idk, ESx batteries suck, they always have some weird issues, but they are safe, they have thick plastic enclosure, spacers, BMS with thermal senors, fuse, etc(cont)
>>1949762>They expect the charger to manage everything regarding safe charging or they make the charger dumb and expect the BMS to handle everything.Charger has just one job, supply CC-CV current. And its BMSes purpose to cut off the charger when battery is charged or about to overcharge. > If the charger fails and supplies too much currentThat's very unlikely. But it can fail in such way it would try to charge the battery way above its rated voltage. Or user-idiot will try to use 48V charger on 36V battery. And in this case BMS is the only thing that can prevent this.>solder traces overheat and fuse together causing a short. This is where ordinary fuse should prevent from shit going nuclear. As I said, a lot of manufacturers just skip it for reasons unknown.> The BMS doesn't have good short circuit detection and relies on the solder joints never failing. BMS has pretty good short circuit protection, it is much faster than normal fuse, but there is a catch. It uses MOSFETs, and they do fail short circuit, which means that in case of some insanely catastrophic short circuit, MOSFET can blow up and it won't cut the current when BMS notices that current is too high. And again, this is where normal fuse should come into play, but sadly, 0.01 cent device is often omitted. It doesn't even have to be a proper glass/ceramic fuse, you can do it like they do it in tesla, where each cell gets a fuse. > The wires are undersized and they count on the consumer never overloading them for too long for it to become an issue.I've never seen an undersized wire on the battery. They are pretty thick, but what I don't like is that they are often silicone, I'd want to see other type of insulation there, which is more wear resistant. Like idk, PVC (which is cheaper than silicone even) or XLPE or smth. >At best the consumer wastes time/money fixing it or deals with premature aging. At worse it starts a fire.Pretty much. (cont)
>>1949762>All of which could have been avoided with proper engineering.There isn't much engineering even needed. It just needs 50 cents more. 50 cents to get proper cell holders with insulators between cells, couple ceramic fuses, couple thermal fuses, etc. >I didn't think of the importer thing. That probably plays a role, It is pretty much an importer problem. They want cheaper, and chinks don't have any regards to safety. I know chinks can make good batteries, hell, even SINC power makes better batteries than I got, because apparently somebody asked them to make it cheaper, so they used BMS without balancing. >but you see the same thing from batteries sold direct from the manufacturer or on major stores like eBay or Amazon.Also an importer problem. But in this case you're the importer, and you're buying junk, that some exporter in china though would be a good idea to order, and again, 10 RMB less? no problem, fuck fuse, fuck BMS, there you go. Battery. It would be 10 000 km away from my home, who cares if it catches on fire.There is nothing wrong in trying to cut corners in order to get lower price, but battery... and other components that can result in property damage and injury, you don't save on them. Worst part is that this short term savings might result in entire shit getting banned like hoverboards, which would result in total profit loss in the long run.
Don't put gas cans in your home. Don't put sketchy lithium batteries inside your home. Keeping the price low to promote proliferation of EVs is acceptable.
>>1949696I couldn't resist to test the results. 13.2 kmBMS still did trip on imbalance, but scooter died in more predictable way, and I think it made 2 km more than before the BMS change.I should add thermal fuse and normal fuse, but for time being, its fine.
>>1949884Fucking shit wont charge over 39.7V...I think I will wait for a day, and if voltage won't go up, or charger won't kick in, I'd disassemble battery again...
>>1949744>Yeah bro it's totally fine any internet retard can do it you just need a bucket of sand go ahead>oh well there is fires but those are coming from factories that don't know what they're doing crazy that I recall a couple months ago seeing a fire at an ebike repair shop. Must have been that someone brought in an AliExpress bike and it blew up before anyone got a chance to open it upit's also crazy that the vape scene had a bunch of the same batteries blow up every so often and now that DIY isn't popular it all went awaybut sure keep dumbfucking around with batteries and encouraging others to then whining 'b-but China' when shit blows up and bans roll in
>>1950017>crazy that I recall a couple months ago seeing a fire at an ebike repair shopThis is normal, nothing to see there.>but sure keep dumbfucking around with batteries and encouraging others to then whining 'b-but China' when shit blows up and bans roll inYep, its china problem, if shit was done right first time, there would be no need to do the retarded shit
>>1950017Learn to read retard.I said if you know what you're doing, not any internet retard.The issue isn't the bike itself, it's the batteries and controllers. Look at power tool batteries and how those are abused. They use the same cells as e-bikes but don't catch on fire because they're properly made.
I've repaired Ninebot ES2 today. God I hate Ninebot ES2, every time I disassemble one, it feels like I'm fisting an android or something, and that would never fucking end since shit keeps on breaking... Makes me wonder if Ninebot-Segway is incapable of designing scooters, or it is just ESx an engineering failure, because I don't think M365s (that were released before ESx) are having so many mechanical issues as ESx. Any segway-ninebot or xiaomi owners? Preferably with high milage scooters. Did you have any weird issues with scooters? Was a broken solder joint inside the battery (thanks EU faggots for lead-free solder). And since BMS design is extremely retarded (you can't disconnect the cells so you have to solder on live board), I blew up a track when re-soldering the connector, had to run a jumper wire.Also they started using EVE cells instead of LG M26, which kinda sucks. Old ninebot batteries were weak as fuck (20A discharge max), but this is just pathetic as cells are rated just 7.5A discharge, which means 10S2P pack would be able to deliver just 15A safely, which is too close to typical e-scooter consumption of 12-13A...>>1949696As for generic scooter in the OP, it did charge to 42.0V in the end, but I kept it charging/balancing for a bit more.Tomorrow I will see if it would do any better. 13 km to beat.
This is how I see Ninebot ESx
>>1950341Okay.... What have happened is that in noname scooter welds have failed, and since i tried to pull off the tabs, i pierced the cell open. Welp, fuck.
later that day... >>1917453
>>1949696I don't understand what you're talking about, so it's no stretch of the imagination that some underpaid chink wouldn't either, or care if they did.
>>1950480It was a close call. I shorted 2 cells, and one was pierced. No fire... yet.Good thing they were charged to 3.7V per cell
I'm looking at my 26 normal cells, 3 burned and one with a hole...Maybe I don't need 36V on scooter. With 24V battery (7S4P) it would go up to 25 km/h (which is legal and reasonable) and losses in battery would be lower, and losses in controller would be lower too. Anyone tried undervolting/overvolting scooters/ebikes? What did happen to wh/km in your case?
>>1950695A top speed of 25 kph may be adequate for you, but you'll be missing out on torque so you're acceleration and ability to climb hills will be significantly diminished. I'd keep it at 36V.
>>1950762>but you'll be missing out on torque so you're acceleration >and ability to climb hills will be significantly diminished.Why though. If current is the same, so given speed is sufficiently low, torque should be exactly the same.Or phase current is different from battery current even on dumb square-wave controllers?
>>1950767I don't know why, I'm not an electrical engineer. I've never used an electric scooter, but for RC cars, electric airsoft guns, battery powered fans, etc. lower voltage battery = less torque.
>>1950780ESCs for RCs are very different, they don't limit current like e-bike/scooter controllers do. They rely on the fact that MOSFETs have headroom and motor resistance is high enough to limit current to acceptable levels. For matter of fact, most ESCs don't even know what kind of current is flowing through the motor, as they don't have current shunts.E-bike (e-scooter) controller needs to have current limit, because winding resistance is so low in most e-bike motors, it would draw insane amount of current from the battery, which would burn the motor, and would require transistors from idk, a train or something, ones that can handle kiloamperes lol. Even at low RPM throttle position. In other words, in RC world torque is the product of battery voltage and resistance of motor, and in e-bike it's a product of current limit of controller (which is much lower than voltage / resistance ). At least I think so.
https://www.youtube.com/watch?v=xBPwZzBhCvESodium Ion cells are real. Are they the future of e-bikes? In capacity they are comparable to lithium cells in 2010-2012. Not great, but given low cost might be acceptable. Seem to be more safe in terms of fires too. Very similar to lithium batteries in terms of manufacturing, with same compounds, except, well, lithium, so production can be sped up fast.Even if they won't become a viable option for cars, it would be great for solar shit, which will reduce demand on lithium which will make it cheaper to have more lithium batteries in vehicles. Also, where tf chinks from aliexpress got them? Mass production test run got recycled by selling to random dudes?
>>1951014https://www.youtube.com/watch?v=W1ya_ls1zkAHmmm... It's a bit more spicy pressure-wise, but less spicy fire-wise.
>>1950785If you use the controller to put out more amps to compensate for the lower voltage you're going to generate more heat and likely lower the energy efficiency and lifetime of the motor. You'll also put more load on the mosfets which will have the same effect.
>>1952397I had to double and tripple check. Motor controller only cares about motor current. So on 36V it would consume less current, than on 24V in order to achieve same power. But. Motor controller is also converts (steps down) whatever battery voltage to match BEMF voltage of the motor, which is dependent on speed. And here is a thing. BEMF of motor at 25 km/h is aprox 24V, which is much closer to 7S Li-ion battery voltage range, than 10S Li-ion. This means that efficiency of motor controller would be higher on 24V, because all DC-DC converters are more efficient if output and input voltages are close.So, overall, what's gonna happen? 1) Acceleration from zero won't change (as controller keeps same motor current)2) DC Current would increase for same amount of power because there is no free energy. Doesn't matter much as wires are short. 3) 25 km/h would become new max speed, as you can't push more current when Vbat < Vbemf4) Efficiency would increase slightlyTwo last points will lead to higher efficiency, because of air resistance (as now scooter is slower), but also because Vbat is much closer to Vbemf (80% -> 90%, which means extra 1.6 km, but probably more because battery was also fucked). But you know, physics paper calculate all is fucking useless, until I do the test.
