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Everything posted by esaj

  1. esaj

    126-Volt Nikola

    Right, didn't consider it from that point of view, good point. Still, while progress is a nice thing, considering the f**k ups of pretty much every manufacturer in the long run, I have my doubts how good idea pushing the voltage up all the time is. I just hope nobody ends up electrocuting themselves.
  2. esaj

    126-Volt Nikola

    If you take X cells with Y amphours, you always get the same amount of watthours regardless of the configuration, for example 100 x 3Ah cells: All in parallel: 3.6V nominal, 300Ah => 1080Wh All in series: 360V nominal, 3Ah => 1080Wh And any combination in between (2S50P, 50S2P, 4S25P, 25S4P...)
  3. esaj

    126-Volt Nikola

    Hope they get the design right, as this requires even better components, higher clearances/creepages on the board etc. The voltages are even more lethal than before and if they keep this up, some regulatory body is going to start looking into the wheels. Don't know the "rules" that closely, but anything over 60V DC is already regarded highly dangerous and there are limitations to selling such devices to normal consumers. Then again, electric cars use several hundred volts (400V DC or something in Teslas?). AFAIK, they don't even use mosfets anymore, but IGBTs, maybe that's the next step for wheels.
  4. There are some links in the first page of the thread about self-powering modules that also do current & energy measurement that cost about the same. Price-wise, any really low volume project just cannot compete with those, plus the Chinese seem to push the components much closer to their limits (the linked module in the above seems to use a linear regulator + a big heatsink, that voltage meter requires only about 1/10-1/20th of the power the BT-module + an actual display would need). I'm constantly on the fence about this, because I personally don't even necessarily need a Charge Doctor-like device (seeing that I already have a working CDv2), but the meter in general might be useful elsewhere... Then again, in my other stuff I likely won't need support for anything like 100V.
  5. Yes, directly on the charger pins, make sure you have the multimeter wired correctly (for voltage measurement, if there are separate jacks for current measurement ) and use a high enough DC voltage range (Usually they're something like 2, 20, 200V for the basic meters, so use the 200V DC area). Unloaded charger should output the maximum voltage, 4.2V per cell, ie. 67.2V for 16S, 84V for 20S, 100.8V for 24S (assuming there are no actual diodes for reverse protection in the BMS). If it's slightly higher (like 0.01V per cell), it shouldn't usually be very dangerous, on a pack with healthy cells, the voltage is divided pretty much equally across all the cells in series, so for example 84.2V / 20S = 4.21V / cell, but going much above starts to stress the cells and in the worst case can damage them, so the safest bet is to stay around 4.2V per cell (some chemistries can handle overvoltage better than others). On some another topic, I think it was mentioned that KS uses 4.24V as the cell overvoltage protection threshold. The passive bleed-balancing should take care of slight overvoltage above 4.2V, albeit slowly. I found out that the Firewheel charger I was using with it was putting out 67.8V (for 67.2V packs) after I had already been using if for quite some time, that's 4.2375V per cell, and I know the pack didn't have any kind of reverse protection (so no diodes dropping the voltage) because I could power things directly from the charge port Apparently it didn't have any overvoltage protections either, because I'd often take the wheel "hot off the charger" and my rides start with a short straight bit and then a couple of hundred meters of downhill without issues, where the regenerative braking was likely pushing the voltage up even more... If the charger voltage's below the maximum battery voltages, the cells will never be fully charged (or some will and others wont, if they're out of balance enough), and depending how high the balancing voltage per cell is in the BMS, the cells might never get balanced and you won't get the full range out of the pack.
  6. For a light-weight rider, the high power can actually be a bit of a problem, not having the body weight to throw around, getting the wheel to respond (especially if its on hard-mode) in an uphill for example can become problematic, as the high power can easily overcome trying to push the fronts of the pedals down and the wheel tends to stay level, not getting enough "feedback" to push up the speed. Then you either need to stand tip-toed on the pedals or try to grab it with your legs and force it to lean forwards. Some people have 3d-printed parts glued to the side they can grab with their legs to get the wheel to tilt forwards and force it to accelerate. I changed my wheel from hard to middle because of this, made accelerating uphills a lot easier and I noticed I like the slight "give" during strong braking.
  7. The question is did it actually cut out (totally lose power, even for a moment, which shouldn't happen), or was it a rider fault with losing balance, or an overlean / too fast acceleration causing the motor to run out of torque (massive voltage drop, possibly with motor back-EMF reaching sagged voltage due to too high speed). Considering what powerhouses the current 18" wheels tend to be, I doubt a 180lbs / 80kg rider with prior riding experience could easily overpower them on accident. Especially the latter incident at low speed (10mph) makes me think this could be a fault in the wheel, unless he's almost throwing himself to a steep forward lean. Of course it is possible to overlean pretty much any wheel, if you really try... I've done those from-sub-walking-speed-to-35km/h-way-too-fast -accelerations on a KS16S, albeit I weight only around 60kg, and never had the wheel fail me (but the sudden tilt-back is so crazy in those situations that I don't do it anymore ). @Captain Ahab: was the battery low at either case?
  8. Unless you're a particularly heavy rider, I'd suspect that there's something wrong with the wheel. On your spills, did it tilt-back at all before cutting out? Were you accelerating fast?
  9. Unless the forum software supports it, unfortunately no. The platform's provided by Invision Community, to my knowledge it's not custom-code to which any moderator (or even admin, ie. John Eucist) could make any changes. Might have some sort of plugin-system though, but I can't access anything except the basic moderation tools.
  10. @mrelwood: you earlier asked about high-temperature wires, at least TME carries some fiberglass-cables rated for +350C to 400C from Lapp Kabel and Helukabel: https://www.tme.eu/fi/en/katalog/heat-resistant-cables_100565/?s_field=artykul&s_order=ASC&visible_params=2%2C529%2C1335%2C2517%2C665%2C669%2C32%2C657%2C18%2C667%2C673%2C663%2C672%2C661%2C2221%2C423%2C2206%2C681%2C683%2C671&mapped_params=32%3A1451325%2C1629996%3B It might make sense to use such cables for the hall-sensors, if you want to avoid from them getting destroyed in case the phase wires melt again. Wouldn't save you from a faceplant / blown mosfets, but at least the motor should be safe Better take a look at the datasheets though, I have no idea how tight turns (minimum bending radius) these cables can make, and if they can fit through the axle with the phase wires (external diameter).
  11. @cgi bought one of the Wate-chargers, no first-hand experience, but apparently they're higher quality than the usual bricks: https://www.aliexpress.com/store/3113065
  12. "Nothing is as smart as an engineer, except a drunk engineer"
  13. I calculated the values for the LTC3638 simply following the datasheet and using a spreadsheet, unfortunately I haven't figured so far how to get it to Google Sheets without breaking the formulas or values changing (for example, we use comma as decimal separator here...) LTC3638_calcs.ods The cells with cyan backgrounds are for input values, rest is calculated based on those: Reason for picking the non-synchronous LTC3638 vs. synchronous LTC3639 was that the synchronous-chip is limited to 100mA max (if it's an absolute maximum, shouldn't draw that much, otherwise risking breaking the device). It might be that the display + SoC + other stuff doesn't need but 50mA, but in case of using a different display or such requiring more current, the 3638 has 250mA maximum, leaving much more headroom. I was thinking of using 5V output, but it could be set somewhat lower, the final 3.3V voltage should be regulated through a linear regulator anyway to filter the noise in the measurement circuits, or if 3.3V is taken directly from the SMPS, the analog-side may need separate filtering. Running an LTSpice-simulation with component values taken from those below (the preliminary parts) and 101V input, the ripple at constant steady 100mA or 50mA draw was only around 25mV, but it's just a simulation, not taking into account the effects of layout for example (current loops around the SMPS), and the actual load has an MCU, which draws current in "spikes" with the clock, although the bypass caps of the MCU should filter out most of it. Also the simulation shows that the output voltage raises above 5V with lower load, so using 3.3V might be a no-go if it does the same (the MCU can't handle but 3.9V absolute max), so probably higher voltage than 3.3V at the SMPS + post-regulation is needed anyway. Isolated flyback might be a better option than "normal" buck-regulation, but I don't have experience in using such, and I doubt this project would be a good place to start learning Seba likely knows much better, so probably best to wait until he's got at least a preliminary design. I won't order the parts for the step-down yet, as most of the the circuitry can be bench-tested with a separate power supplies, and for load testing I'll need something more powerful anyway, my adjustable 0-100V max linear PSU is only 100W anyway (limited to 1A max at any voltage, so it can only reach 100W with 100V output). At least it does have ability to push the voltage up to 120V for a short while (+-20% buttons), for line transient / overvoltage testing. I can start poking into the actual measurement circuits using what I have at hand (General purpose Cortex-M's without BT, op-amps, current sense resistors, displays...) in the mean time. Preliminary parts for the step-down: (amount) (manufacturer) (part number) (specs) (Mouser prices in € without VAT: x.xxx < 10 pieces / x.xxx 10-99 etc., the price breaks) Diode: 1-2 ST Microelectronics STPS1170AF 170V / 1A / 0.62Vf / SMAflat 0.384 < 10 / 0.299 10-99 / 0.12 100-999 2 if using the same diode for input protection before the step-down Inductor: 1 Laird Performance Materials TYS6045680M-10 68uH 20% Shielded / 1A / 289mOhm / 6x6x2.8mm 0.297 <10 / 0.286 10-24 / 0.268 25-49 / 0.261 50-99 Input caps: 3 Yageo CC1206KKX7RABB104 100nF / 200V X7R MLCC / 20mOhm @ 40kHz / 1206 0.262 < 10 / 0.177 10-99 Might also be 220nF, haven't checked options further yet, likely the input capacitance should be made higher than this to minimize input ripple (the Delta_Vin used in the spreadsheet is pretty large at 5V... ), more like a couple of uF? SS-cap (100nF actually makes the soft-start last 16ms): 1 Murata GCM155L8EH104KE07D 100nF / 50V X8L MLCC / 300mOhm @ 40kHz / 95nF @ 5V Bias / 0402 0.087 < 10 / 0.071 10-99 100nF's will likely be needed all around (bypasses to MCU, amplifier, linear reg...), so the actual amount is more, something like 10. Output caps: 2 Murata GRM21BC71C106KE11L 10uF / 16V X7S MLCC / 10mOhm @ 40kHz / 6.3uF @ 5V Bias / 0805 0.384 <10, 0.269 10-99 / 0.176 100-249 1 Nichicon RNE1C101MDS1 100uF / 16V Polymer / 35mOhm 0.533 <10 / 0.396 10-99 / 0.272 100-499 LTC3638 7.72 < 25 Resistors: Basic 1% is probably accurate enough for UVLO/OVLO (have to take into account the voltages with package sizes, ie. clearance / creepage, 0805's seem to be usually rated at 150V max, so maybe 1206's)
  14. Why not, but it doesn't make it much more complex to add the current monitoring and thus the ability to calculate watthours going into the battery. In both cases, the MCU will still need around 3.3V voltage, which needs to be stepped down from up to a 100V and change (even slight overvoltage).
  15. If you need a reliable low voltage lab PSU in the future (for guitar pedals or whatever), look no further than HP6632 (A or B), which are relatively easy to find as second-hand, this is a serious industrial-grade 100W programmable linear lab rack PSU from the 80's/90's (production discontinued in 2017) with proven track record. East Trade Promotion sells such for example (not sure if they have any in stock right now, but there have been plenty in the past), I bought mine from them through huuto.net: http://sivut.klikkaa.fi/eastrp.fi/webshop/product_details.php?p=45 https://www.keysight.com/en/pd-838596-pn-6632B/100-watt-system-power-supply-20v-5a?&cc=FI&lc=fin (The reason the specs are in Keysight-website is that HP instrument-division first became part of Agilent and then Keysight) Output Ratings Output voltage: 0 to 20 V Output current: 0 to 5 A Programming Accuracy at 25°C ± 5°C Voltage: 10 mV + Current: 0.05% + 2 mA Ripple & Noise (20 Hz to 20 MHz) Voltage Normal Mode rms: 0.3 mV Voltage Normal Mode peak-to-peak: 3 mV Fast mode rms/ peak-to-peak: 1 mV/ 10 mV Current rms: 2 m https://www.eevblog.com/forum/reviews/hp-6632a-20v-5amps-programmable-psu/ "They are super precise , and can sink & source current.The meters are/were the most accurate i had when i bought them." Mine was off by about 4mV (0.004V) higher up in the voltage, that's about it. Hasn't been calibrated in 10+ years. In a pinch, it'll work also as a load up to 20V/5A, although at least on mine the down-programmer has an issue where the sinked current will be about 250mA higher than what's programmed, guess it's an general issue (it's not like it was meant to be used as such ): https://www.eevblog.com/forum/testgear/hp-6632-current-sinking-performance/ Not that big of an investment money-wise (I think I paid 120€ for mine with rack-ears, including shipping), the size might be an issue (2U rack-unit), plus it weighs 10+kg.
  16. Oldish topic, but I decided to play a necromancer.. How have you guys found a big change in tire pressure changes the ride behavior? I've favored high pressure (over 4+ bar / 58+ PSI) due to how much "faster reacting" it makes the wheel, not to mention that I get much better mileage at high pressure (can't quote exact numbers, but I'd say 1/3 to 1/4 more mileage vs. really low pressure, like 2-2.5 bar / about 30-36 PSI). Now, I've tried different pressures a long, long time ago with the Firewheel, and found out that I favor the high pressure over lower pressure (especially since my FW had such a small battery at 260Wh, more mileage ), despite making balancing at any speed much more delicate. Usually I've topped up the pressure after two-three months, but this time it seems my tire pressure had been dropping faster than usual. I think I've also been riding faster than usual lately, with average speeds topping 30km/h (yes, yes, I know it's not "that fast", but it's a KS16S ). I'd consider myself a fairly experienced rider (but there are more experienced in the forums) after something like maybe 10k+ km behind me (I don't know, I stopped measuring a long time ago, but then again, I only get to ride 5-6 months per year, since spring of 2015). So, early this week I noticed my tire pressure is getting really low, since I could just "bounce" on the wheel (can't say exact figure, since my car-battery powered -compressors' meter doesn't seem to even react to anything below 2.5bar or thereabouts), and was worried I could cause a "pinch puncture" riding over some corner stones or whatnot. The bright side was that slight irregularities on the road felt like nothing, and I could ride fast into turns with no issue (although at some point I likely would have hit the pedal on the ground). I pumped up the tire until the compressor said something like 4.3-4.5 bar or thereabouts. I pump the pressure "over", because some of the air always escapes removing the compressor nozzle and the valve extension, and the final pressure could be more like 3.5-4.0 or something like that. Probably should invest in a pressure meter to know better Also the cheapest battery-powered compressor in the hardware store probably doesn't have the most exact measuring. Anyway, this time I managed to rip out the nozzle and extension really fast, with very little loss in air. Of course I didn't test the wheel afterwards, as it was late in the evening, just went to sleep. The next morning when I rode to work, holy hell, was the wheel acting strange. The tire was super hard, I've used to feeling small pebbles and such on the road, but now it was like the tire had zero give at whatever slightest irregularity the road might have. The wheel was super sensitive to even my slightest move, and would start to wobble on its own riding straight on a more or less even road. But the biggest surprise was the effect on cornering. I'm used to riding pretty fast into 45 or even 90 degree wider turns, when there's not people around and I can see that I'm not going to hit anyone after the turn. Also, I'm used to leaning more on my body, and only more slightly tilting the wheel on turns, like "leaning out" from the wheel, allowing the foot opposite to the turn to lift off a bit from the pedal, remotely what you'd do on a motorcycle pushing your knee out and "hanging" from the bars, leaning out from the bike, but this was much different to before. The wheel seemed to stay more upright, like totally upright, and resist me trying to tilt it with my calf. This was at speeds something like 25-30+km/h (first warning playing) and change, tried it a couple of times. After a 5-6 kilometers, I had to stop and let some of the air out to ride rest of the way. I don't know where I dropped it, likely something like 3.5-4 bar, since it's more like usually after filling up the tire. What most surprised me was the cornering behavior, since the wheel "fought back" on leaning sideways a lot more than what I remember having experienced before. I'm a lightweight rider (probably pretty close to 60kg/ 130lbs in full gear), so heavier riders might not have the same effect, but it certainly made my turns much wider than usual at higher speeds. In lower speeds, I could still ride fine at sub-walking speeds, while simultaneously opening my helmet and lighting a cigarette, so at low speeds it seems not to be much of an issue. Might still be that I'll start to prefer using lower pressures (but not too low ), considering that allowing the pressure to drop, it made fast speed riding far more stable ("you haven't lived until you make a tight 90-degree turn with full tiltback"... nah, actually, I don't recommend it ), and riding at slug pace was even easier than with high pressure. Of course on the low end, you're going to likely hit a point where it becomes an issue (I was already noticing that I was using more battery than usual and probably would have hit the pedal on the ground sooner or later on a tight turn).
  17. Was going to write about the same thing, but you got it first... Yeah, the 24S packs will have higher internal resistance, couple that with less packs in parallel, it might be that the 100V versions actually have lower maximum (safe operating range) power output vs. 20S, and the only upside is (up to a point) higher top speed. But there are a lot of variables at play, so it might well be that the the internal resistance of the battery packs is not the main issue.
  18. Oisko sisäpuolella sen verran tilaa että nuo vois vaan pultata jos tekis reiät koteloon? Ei tarviis arpoa että irtooko Muistaakseni joskus koittaessa tuota lakia tulkata, siellä oli vielä erikseen pätkä joka sanoi että "itsetasapainottuvat" vehkeet joita saa ajaa jalkakäytävällä pitää olla sellaisia että ne pysyy pystyssä paikallaan ilman kuljettajaa, mikä käytännössä tekisi kaikesta alle 3-renkaisista laittomia jalkakäytävällä (ei pyöräteillä/kevyen liikenteen väylillä), kun ei ne itsekseen paikoillaan ja pystyssä pysy. Tiedä sit miten sitä käytännössä tulkitaan.
  19. esaj


    I must admit that I didn't watch the videos, but I did get one of those DSO-scopes (a DIY-version, with no enclosure) back before I bought the Rigol, and already have one cheapo LC-meter (Ie. "just" capacitors and inductors, no resistors/ESR like the LCR-meter, cost about 20€, a good quality basic LCR-meter is maybe 100-200€, professional-level high precision meters of course go up into thousands as usual ) and a simple semiconductor/component tester (which also can measure capacitor ESRs, although probably not very precisely). These kinds of devices aren't really bad for their price in general, and good enough for general hobbyist usage, but I have no real use for the cheap stuff anymore really, what I'd likely need next is a more "serious" high-power lab PSU (Still looking at that 150V / 1.5kW TDK-Lambda Genesys) and another scope with much lower noise-floor, the Rigol's otherwise nice, but the noise generated by the scope itself is around 800µV, which is pretty bad considering the (possible) CD-project. What I was going to do this summer was to get my electrics rebuilt in the house... Not only would a 1.5kW power supply (if used at full power) put more stress the cabling, my current setup already likely does run pretty close to the limits This room + the one next to it comes through a single feed behind a 16A fuse, and I could be using several kilowatts already here, plus the next room has a freezer and wheel charging... All the wiring and mains cabinet is original from over 30 years ago. The house across us burned down due to electric fault in the mains cabinet a couple of years ago I sent an email to 10 companies asking for an offer, 2 responded (it's been a month or more), and at least one of them fell out directly due to the price they were offering, the other came by to look at things, and promised to send an offer later, but I haven't heard back. Looks like it'll be sometime in the future then...
  20. It may make sense in special-cases, like things that are built-to-order (and usually cost some serious $$$, like >1GHz scopes, only directly from manufacturer, prices are 5- or 6-digits), people building analog audio circuits like pedals and analog synthesizers (like a friend of mine who "lives" in our garage during the summer, building cases for them ) often have to go that route (matching components and whatnot). Never really dug deep into there, as I haven't been bitten by the bug (yet ). As for resistor tolerances, 1% basic resistors cost about 1cent/piece these days when bought in lots of 100 pieces or more, so I haven't seen the need to use 5% or more tolerances, the savings are nothing. J-Fets might be different, and like said above, analog audio circuits are a special case really. For mass-produced consumer products, I doubt the manufacturers would go the way of matching components, but likely mosfets bought at the same time are from the same batch. In general, many EE's seem to frown at paralleling mosfets instead of using higher rated single mosfet, it's considered bad practice, but it can often be cheaper to use two cheaper mosfets in parallel than one better rated one, which likely is the reason the wheel's use parallel configurations instead of "proper" single device. At least Toshiba, IRF/Infineon and Nexperia have published longish application notes on problems and issues with paralleling power mosfets specifically, and at least Infineon and Nexperia suggest that optimally the mosfets should come from the same batch if parallel configurations are used, but mostly it's just a matter of handling the gate drive "correctly" to avoid parasitic oscillations. https://assets.nexperia.com/documents/application-note/AN11599.pdf https://www.infineon.com/dgdl/para.pdf?fileId=5546d462533600a401535744b4583f79 http://www.irf.com/technical-info/appnotes/an-941.pdf https://toshiba.semicon-storage.com/info/docget.jsp?did=59458 In the past, I've done exactly one device which used paralleled mosfets (5 in parallel), but it could put out >1000A in short spikes (1-10 milliseconds, spot welder), and I followed the application notes on the basic suggestions how to ensure the turn-on and -off don't cause problems and the load is shared as equally as possible (gate resistor with anti-parallel diode to speed up the turn-off, ferrite beads to increase high frequency impedance and kill off parasitic oscillations). All the mosfets were ordered at the same time, so likely the same batch. For anything "critical", I wouldn't order the parts from Aliexpress or such, you can never know whether you get some other mosfets with changed "stamping" on the package, clones, used devices removed from a broken device, factory rejects (don't fulfill the datasheet specs) or the genuine thing. If the capacitors are discharged, you may or may not get sparks, it's all down to how good a connection you do (and how fast). The initial current when the capacitors sit at (or near) 0V, and a battery pack with 60...80...100V or whatever is connected, can be huge. If the connectors are touching "badly" (only slightly), the highest resistance point is at that connection, yet the resistance may still be low enough to allow substantial current (like 100...1000+A in a very, very short spike). Most of the voltage gets dropped over the highest resistance in the circuit, meaning most of the power is dissipated there, and the short-lived but very high power dissipations there (think 10kW or such, the above 1000+A spot welder used 12V and could go above 10kW peak when the "short circuit" starts) is enough to melt small amounts of metal (that's the sparks you see, tiny molten bits of copper or whatever the connector's made of). The battery BMS's have (or at least should have) short-circuit protections, but they still take few milliseconds to react, which is too slow to prevent this. The "anti-spark" XT90's have a clever internal structure where the connection is first made over a resistor that limits the current, but is low enough to allow the capacitors to charge before the final very low resistance connection is made, and at no point the current spikes into really high numbers. Been there, done that... Luckily no other damage than a destroyed probe and XT60-connector.
  21. Don't look too much at the wattage/current absolute maximum -numbers given on the beginning of the datasheets, they're theoretical at best and cannot be attained in reality (at least not without very efficient cooling, like pumped liquid with large external radiator or liquid nitrogen or something, and even maybe not then ). To use IRFP4468 as an example, here's how they arrive at that 520W number: Starting point: Ambient temperature at room temperature (usually 25C in datasheets). Case (package) at ambient temperature. Junction-to-case thermal resistance is 0.29C/W (ie. the junction temperature goes up 0.29 celcius above the case temperature per watt of power dissipation). Maximum junction temperature is 175C. So, assuming the case would magically stay at the same temperature regardless of junction temperature and the heat coming out from the junction wouldn't warm its surroundings, so-called "infinite heatsink-model" where the case temperature never raises, you could theoretically dissipate: Maximum power = (Maximum junction temperature - Case temperature) / (Junction-to-case thermal resistance) (175C - 25C) / 0.29C/W = 517.241W Round that up to 520W for good marketing material. The device would be working right at the theoretical maximum junction temperature limit (175C), and any external heating, or the case heating up, it would likely die. If it can even survive up to (exactly) 175C junction temperature. The thermal resistance between the case and ambient (case-to-sink + sink-to-ambient -thermal resistances) would have to be 0C/W. If the board's getting hot enough to melt solder, the ambient, sink and case temperatures are something totally different than 25C Similar "magic" is often used in the calculating the theoretical maximum currents, so you can forget about things like "single mosfet could handle the entire current, it's rated at xxxA!" if just looking at the absolute maximums. I don't know how the peak pulse currents are calculated, heat doesn't move at infinite or "even" light-speed, so with a large current spike, the heat doesn't even have time to conduct away from the junction... They're not outright lying, and all the manufacturers use similar techniques to calculate the maximums (so they look as "good" as the competition), but you can never get to those numbers in the wheel, maybe on a lab bench with very heavy cooling, for a short while. Also, typically the mosfet legs will melt before such figures are reached continuously or in average anyway (that's the "package limited" -value), pulsed they can probably handle high currents for a while, at least if allowed to cool in between. If you compare the Rds_on -resistances, the list looks like: HY5012: 2.9mOhm typical, 3.6mOhm max IXFX300N20X3: No typical given, 4mOhm max IRFP4468: 2.0mOhm typical, 2.6mOhm max IXFH320N10T2: No typical given, 3.5mOhm max You'd want as low as possible resistance, so as little as possible of power is "wasted" in the mosfet, heating it up. Another thing to note here is that the IRFP4468 and IXFH320N10T2 are a 100V mosfets, whereas HY5012 is 125V and IXFX300N... is 200V Vds max. Without knowing how high voltage spikes the motor can put out, going lower than the original might be risky. Also, I'm a little bit suspicious of the HY5012-numbers, IXYS and especially International Rectifier (nowadays owned by/part of Infineon) are big brand names in mosfets with long history and breakthroughs in manufacturing technology, a little hard to believe that some never-heard Chinese manufacturer (Hooyi?) is producing mosfets with better specs. I'd go about selecting in this order: Original (no risk of issues with wrong ratings, since it has worked in the past... well, until it blew ), or if not available/not an option, same or higher Vds_max -voltage as original with same or lower Rds_on -resistance as original. Obviously the same package (TO-247 in this case). Preferably same'ish gate charge, although someone with an EE -background once said that it likely doesn't matter that much in wheels, since the wheels use (relatively) low switching frequencies and powerful gate drives, but if the gate charging and discharging has been more or less "optimized" for some gate charge (it probably isn't, at least with GW), the gates in the new mosfets might charge/discharge too quickly (lower gate charge, possibly causing gate ringing) or too slowly (higher gate charge, excessive switching losses passing through the linear region on turn-on/turn-off). But probably it's not an issue in reality here. Safest bet is to get a whole new board, followed by replacing the mosfet with the same model as the original, followed by using another type of mosfet. Like Marty said above, there is a risk that something else has been damaged along with the failing mosfet, so it's not certain the board will work flawlessly just by replacing the fried fet, although people have replaced fets before and had the wheel working again without an issue.
  22. Oh yes, motorcycle- or traffic cops might be more "educated" on the subject. And if they can get a radar reading of your speed, and it's clearly above 25km/h on level ground (or even uphill), then things might get different...
  23. I've bashed Gotway (without ever owning one ) in the past, but this debacle isn't exactly anything we haven't seen before. Granted, GW is probably the only manufacturer that more seriously pushes the envelope (KS and Ninebot have been catching up though), but at what cost? Failure rates of EUCs are higher than most types of vehicles, but subjectively it seems GW's still leading the pack there (too)... KS has been more conservative with their designs, but they've also had issues with newer wheels (at least the lock-up and shaking issues with the newer KS18's), after a good run with the KS16-line, which had the lowest number of warranty issues a year or two back on the reseller statistics published somewhere in the forums, but those are probably outdated. And even then, the warranty-repair rate of over 1% of KS16S wasn't exactly stellar (that's still more than 1 in 100). CGI lately got a KS14 replacement board from them that had the battery connector installed in reverse (wtf?) and fried the charger and the new board. Ninebot seems to concentrate more on the (likely far more lucrative) e-scooter -business, after Z-series hasn't exactly been shining in reliability, although it seems to be mostly issues with the battery drain, and there have been rumors here that they might be leaving the EUC-business all together. InMotion had really serious battery issues with the V10-line (don't recall the model, V10F or something?), that could catch fire by itself if moisture creeped into the battery packs. GW, Ninebot, KS and InMotion seem to be pretty much the big 4 nowadays. On the smaller brands, after a couple of years of hiatus, Rockwheel released GT16, but the V1 had lots of problems, don't know how the newer V2 has fared, better I assume, after GR16 I haven't really followed up on them (and that was already released before I got here... 2014?). Supposedly they do have a new model (GT16S / Iron) coming out, but it hasn't been released yet to my knowledge. I haven't followed up on IPS, but looks like they're more or less dead in the water, I5/S5 were the latest models? IPS has had a relatively good track record on reliability, as far as I remember, but they've never made a real high-performance wheel. Maybe they're just cooking up a new model, and taking their time, which probably is not a bad idea. That's pretty much all the "bigger" manufacturers that come to mind, even though EUCs are relatively new (Solowheel early this decade, 2012 or something, the Chinese manufactures emerging somewhere around 2014-2015?) a lot of manufacturers have already disappeared entirely from the scene. We may be in something like the "Model-T -era", but I'd expect better reliability from these things, especially at the current speeds, considering how much more worse a failure can be if you're travelling at something like 30mph or such. Some people have suggested that the manufacturers should follow something more like the automotive / aerospace industry standards, but likely fail to understand the costs of such (a friend of mine, who's a helicopter mechanic, once told me that a single specially built bolt to a chopper can cost >60€ per piece, more complex parts can easily be thousands) and especially on cars, the economies of scale. Some car models are built and sold in the amounts of hundreds of thousands yearly, and in total there are millions of cars built and sold yearly, the entire EUC business is a small fraction compared to that. The requirements are much stricter, and still there are issues with them at times (albeit usually much "milder"). The cycles are longer, and more time is taken to test things thoroughly. While the software is complex, I know that the piece of software I wrote a couple of months ago won't be in real vehicles (not cars, btw) until about two years from now. Before that, it has gone through a lot of testing, and possible bugs should have been found and ironed out (hopefully... ) But maybe a lot of it comes down to us "consumers". We want (demand) more speed, more features and more power on the wheels, and we want it now, not year or two down the road. This puts pressure on the manufacturers to come up with new, faster, bigger and more powerful models, while making it look "sexy" on the outside or something and hasten the development cycle, maybe even skip proper testing, before putting the new model on the market. Unfortunately, this seems to be a somewhat general trend with many products worldwide. I started working professionally in the software-business in the latter half of last decade, when the "agile development" was picking up pace, and while it can produce good software when done "right", it feels like a lot of companies just use it as an excuse to push out their product earlier, develop things in shorter cycles and do the beta-testing on the users. I've heard the term "time to market" a bit too often. And "software can always be updated afterwards and bugs fixed, since nowadays everyone has Internet and everything's online" At times, it seems this is what's happening with the wheels also. Unfortunately, a hardware or software bug there can have much more dire consequences than with (non-critical) products. Slowing down the pace might not be a bad idea. More careful design and planning of the entire assembly procedure, proper testing cycles etc. would likely probably bring down the failure rate a lot. But that means that the buyers will need to wait longer, and many people seem to be "conditioned" to always get the newest and latest on everything. Why buy the model that has been proven over a year or two, when the new, shinier and "better" model is available very soon? The marketing on most things seems to be feeding this, you just have to get that new phone model, the 1 or 2 year old one you have isn't that good anymore I was reading the hardware product design article-series someone linked to a while ago, and while it had good points, it ended with the "planning the product lifetime" or something along those lines, which basically stated that when you're finishing up your current model, most products have a lifecycle of 18 months(!) and you should start planning how to fade away the old model and how to get people to buy your next, better, shinier product... Don't know how much of any real use my drunken ramblings are, likely none, but that's my 2 cents anyway...
  24. If the wheel's being used all the time, likely it won't sit at high charge for a long while, so mostly the degradation likely comes just from the general cycling of the battery. The degradation in storage seems to mostly occur over longer time, depending on temperature (who'd really keep their wheel at 40C or 60C = 100-140F? ) and varies with state of charge: Temperature Lead acid at full charge Nickel-based at any charge Lithium-ion (Li-cobalt) 40% charge 100% charge 0°C 25°C 40°C 60°C 97% 90% 62% 38% (after 6 months) 99% 97% 95% 70% 98% 96% 85% 75% 94% 80% 65% 60% (after 3 months) Table 2: Estimated recoverable capacity when storing a battery for one year. Elevated temperature hastens permanent capacity loss. Depending on battery type, lithium-ion is also sensitive to charge levels. ( https://batteryuniversity.com/learn/article/how_to_store_batteries ) Apart from the early "generics" (14" Airwheel X3-copies that were rampant back in 2015) and a few less known manufacturers that disappeared from the markets years ago (F-wheels used to have LiPo-packs?), I don't think any wheels used anything but big brand-name cells. Smaller capacity, but higher discharge chemistries have been used in some Gotways, I think. In the end, the voltage's going to cause a faceplant if you go fast enough (the motor back-EMF raises to the battery level => no current, no torque).
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