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Everything posted by esaj

  1. This is by no means anything "official", or complete, and everyone's welcome to chime in to propose new/missing/alternative terms and/or corrections. The point is to explain and make the terms less ambiguous and to help with understanding especially some of the more technical topics and discussions here. The usual term used for the electric unicycles has usually been an "EUC" (for Electric UniCycle). John Eucist has explained the reasons for using this term pretty well here: http://forum.electricunicycle.org/topic/119-why-am-i-calling-electric-unicycle-euc-for-short/ , so I don't see the need in repeating. More informally, most people refer to them as "wheels" (wheel in singular form). EUC Parts At simplified level, you could say an EUC typically has four parts: Tire/pedal assembly with a motor in the hub, a mainboard, a battery or batteries and the shell keeping everything together. Battery Battery is the part of the unicycle that stores the energy to move the motor and power the electronics. Most wheels use a battery pack made of Lithium Ion -cells (of which there are many different chemistries, brands and models), typically 16 (around 48-67V empty/full) or 20 (60-84V) cells in series to get the high voltage required to drive the motor, and one or more of these packs to gain high capacity. The total capacity of the battery packs are usually shown as Watthours (Wh), and on average it seems 10-20Wh are needed per kilometer ridden, although this may vary between different EUCs, riders and riding conditions. EUCs with higher battery capacity (usually done by adding more 16/20-cell series in parallel and/or using higher capacity cells) don't only go for longer on single charge, but they usually keep their torque high longer even when the battery has depleted more. BMS (Battery Management System) This is a printed circuit board (PCB) usually located inside one or more battery packs (although in some cases, like at least some IPS models, it can also be integrated directly into the mainboard). The BMS takes care of controlling battery charging, cell balancing, and has some protections (which can sometimes be even dangerous 2017 update: dangerous BMS overdischarge protection problems seem to be a thing of the past), like overdischarge- (low voltage/undervoltage), overcurrent-, short circuit-, and overcharge-protections. Firmware Firmware is the piece of program in the mainboard that has all the logics for the wheel: alarms, speed limits, tilt-back, motor driving logics, balancing the wheel, communicating with a possible mobile phone app over Bluetooth or such, different types of monitoring and alarms (overspeed, overheat, low battery, over-tilt...) etc Hall-sensor Hall-sensors are sensors that can detect a magnetic field. There are such sensors inside the motor that are used to detect the position and RPM of the motor. The mainboard logics need this information to drive the motor. Also the electrical current sensing of the mainboard is commonly done with a chip based on the hall-effect, which is also needed for certain types of motor driving algorithms like Field-Oriented Control and to detect situations where the power output is nearing the limits Mainboard This is the "heart" of the electric unicycle, typically a single printed circuit board (PCB) inside the unicycle, although sometimes there may be more than one board (for example, Firewheels have two boards, the secondary PCB controls things like lights and battery display). Mainboard does and has things like the main MCU (MicroController Unit, the "CPU" of the wheel), driving logics and power feed for the motor, gyroscope and acceleration sensor (MPU, Motion Processing Unit) for balancing and usually something like a Bluetooth-chip for app-support, display control etc. Motor Motor is the thing that moves the EUC. Typically these are 3-phase BLDC/PMSM (Brushless Direct Current / Permanent Magnet Synchronous Motor) outrunner hub-motors with direct drive (with the exception of some geared EUCs, like certain older Rockwheels, secong gen Gotway M10's) that is placed in the center of the rim of the tire. Motors have rated and peak power ("wattage"), and the general rule of thumb is "bigger is better". Bigger wattage does not necessarily mean more speed (although that's possible too), as the different motors can be built with different things in mind (speed vs. torque), and there may be maximum speed limitations in the firmware, but higher powered motor can usually keep you balanced in more extreme situations, like going over a bump or a pothole at higher speed. Especially heavy riders should look for high powered (800+W rated?) motors. Pedal Pedal is the part on top of which you place your feet when riding. Typically made of aluminum or steel, there are various shapes and sizes, and they affect the riding comfort of the wheel substantially (especially on longer trips). Also the pedal clearance (height from ground) plays a role in riding, as low clearance can cause the pedal to hit the ground while leaning. The part connecting the pedal to the motor is commonly called Pedal arm, although other names have also been used Shell Shell or shells are the plastic covers within which the other parts (mainboard, batteries, tire/motor-assembly...) are enclosed. Older wheels used to have a single shell made from two parts, more modern wheels commonly have 4 parts to the shell, the "inner shell" that usually only covers the motor and to the outside of which the batteries and mainboard etc are connected, and separate "outer shells" that protect the electronics and the batteries. The difference is that the ones with separate inner and outer shells are much easier to work with if having to do repairs or such. Strap Strap is a piece of ribbon that usually comes with the wheel. The point is to attach the strap to the wheel handle (or similar), so you can prevent the wheel from falling over or getting away from you when dismounting during practice. Most people stop using this after initial learning, although some keep using it, as it can prevent the wheel from keeping rolling on by itself in case of a dismount. Tire Tire (or is it tyre?) usually refers to the outermost rubber part of the tire, but can sometimes be also used to mean the inner tube ("inner tire"). Probably pretty much everyone knows what these are, so not that much point in explaining further... EUC "tech-talk" Cut-off or cut-out There are actually (at least) two types of cut-offs that can occur with an EUC: the first is what I've called "mainboard induced cut-off" or sometimes I've also used the term "[motor] shutdown" or "[high/max]-speed cut-out", and the second is the BMS cut-off. (2017 notice: most wheels nowadays don't seem to no longer cut the power at high speed, "overlean"/"overpowering" near the top speeds or board failure is more common cause of such falls) Mainboard induced/motor shutdown/high-speed cut-out/max speed cut-out: In this type of cut-off, it seems that the mainboard firmware decides to cut the power to the motor for some reason (at least overspeed/too much current passing through the board or the wheel has tilted more than 45 degrees). When the mainboard does the cut off, the wheel doesn't usually totally power down, but keeps playing a warning sound or something to tell the user that the wheel must be reset before it can be ridden again. I have also thought that this might ALSO be BMS-related, if it's the overcurrent/short circuit protection of the BMS triggering, as those don't seem to latch, but release automatically? So the entire wheel would turn off for a split second... (2017 notice: this seems to be pretty much a thing of the past, at least in the mainstream big-name wheels, like KingSong, Inmotion, Gotway, Ninebot...) BMS Cut-off is caused by the overdischarge (undervoltage) protection circuitry in the battery BMS triggering, and usually cuts ALL power to the wheel immediately. This can be particularly dangerous, as it can occur very unexpectedly, causing the rider to fall almost every time. Typically the protection is latched, so if your wheel shuts off and doesn't turn back on until you've plugged it in charger, it was probably because the overdischarge protection had triggered. (2017 EDIT: Link to BMS-shunting thread removed, not necessary anymore) Reset Resetting a wheel means turning it off and back on. Many wheels require you to do this, once the motor shutdown has triggered, although some automatically reset when turned back upright after a fall. RPM (Rounds per minute) RPM is a measure of the turning speed of the motor, how many total rounds (turns) the motor does per minute. Shunt Shunting a wheel means bypassing the discharge-side protection circuits in the battery BMS to prevent the BMS cut-off. Not needed in wheels made after something like late 2015/early 2016? MOSFET "Metal Oxide Semiconductor Field Effect Transistor" , a type of power transistor used in the mainboard (usually in a group of 6 or 12) that's responsible of driving the motor by controlling current flow in the 3 phases. Commonly referred to when speaking of the technical details of mainboards, or when someone has a burned board (one of the most common reasons of failed board is burned MOSFETs). EUC Riding Idling Idling is the term for staying pretty much in place by moving the EUC back and forth. This is taxing for the motor (constantly changing direction) and eats up your battery fast, but can be useful for example to wait for a traffic light to change or such. Leaning Leaning refers to using your body to move your center of gravity and control the EUC. You lean forwards and backwards to accelerate/decelerate or change direction. To turn the EUC, you usually lean to the direction you want to turn to (left or right), somewhat similarly as with motorcycles or bikes at faster speeds, although you can also use your hips to "swivel" around for tight in-place turns, at least in slow speeds. Out-lean or overlean Out-lean / overlean is a term used to refer to a situation where the rider leans (usually) forwards so much that the wheel cannot keep him/her balanced anymore (not enough torque), and usually ends up with the rider dismounting (or falling). Out-leaning usually occurs near the top speeds or in uphills, where the wheel motor cannot keep producing enough torque to keep the wheel upright as the rider keeps leaning forward. Usually it occurs only after the full tilt-back (but not always, especially when accelerating fast, the wheel may not have enough torque to tilt-back), so most people shouldn't be able to do it accidentally, unless it's due to low battery (if the tilt-back is based on speed). Overpower Overpowering a wheel refers to similar situation as with out-lean and is often used as a synonym, but seems to be more commonly used to describe a situation where the wheel cannot keep you balanced on level ground, for example when hitting a pothole that causes the wheel to tilt too much to forward or simply out-leaning. Overspeed "Overspeed" used to mean the speed where the mainboard cuts the power to the motor. This was (at least mostly) with older, pre-2016 wheels. Nowadays (November 2017) most wheels will let you push it all the way to the end, but once you hit the max speed (which is at least somewhat dependent on the battery charge state), the voltage difference between the battery and the motor back-EMF (voltage induced by the turning motor) is too low to cause enough current and thus torque, and the rider ends up overleaning the wheel. Power braking This is a pretty "unofficial" term, used to mean the type of braking where you push the wheel in front of you with your legs while simultaneously leaning back and pushing the pedals down to brake as fast as possible. Requires some practice, but not that difficult, and a useful skill when you need to stop "on a dime". Be warned though, on occasion this has led to the mainboard burning the mosfets, although it's not common, especially in the higher end power-wheels anymore. Tilt-back Tilt-back is a safety measure, where the wheel starts to tilt the pedals backwards at higher speeds to warn and prevent the rider from leaning more forwards. While it is possible to lean more and try to get more speed, it might not be wise, as you can overpower the wheel. Most wheels have this (many wheels let the user adjust the tilt-back speeds with app), but some older ones don't have it at all (for example older Gotways and Firewheel).
  2. What Are Your Favorite TV shows?

    I read the book quite long time ago, it was actually fun to watch since I had completely forgotten most of the plot and the ending. Of course no TV-series can ever be as good as the book... Still waiting for https://arstechnica.com/the-multiverse/2015/06/syfy-to-adapt-and-film-dan-simmons-hyperion-as-an-event-series/ but I guess it might have been cancelled. Also wouldn't mind if most of William Gibsons' production were brought on screen. Or Neal Stephenson's Snow Crash. Or Stephen King's entire Dark Tower-series...
  3. Ever Buy Stuff That You Probably Don't Even Need?

    The company we order our phones from didn't have anything with real qwerty-keyboard (which these days is pretty much limited to the new Blackberries), but then I found out that they had the Cat-phones I haven't had much real use for it since checking the ceiling heating panels, should go shoot in the attic to see if there are heat leaks... other than that, I plan to use it for much faster detection of burnt components or components running hotter than they should on boards. One thing about thermal imaging is that different surfaces not only emit heat at different efficiencies (emissivity) but also reflect heat. Thermal camera is not an "x-ray" -device, it cannot see through things, and "reading" the temperature values correctly from the pictures is a skill of its own (which I don't really have). Just because something looks warm on the image doesn't mean it actually is, try for example pointing the camera to something metallic like a spoon while you stand close to it or move your hand towards it while shooting... the surrounding thermal (infrared) radiation and your own body heat will reflect from it, and it will look (much) warmer than it actually is. On the other hand, something might appear hotter/colder on the image than it is, because it emits less of the heat and/or the emissivity setting of the camera is wrong. There are tables available, and the FLIR-app on the phone has a (crude) setting for the emissivity, but not actual values, just something like "Matte, Semi-Matte, Semi-Glossy, Glossy". What can make it even harder is that things that don't look that shiny/reflective to our eyes (visible light) still might be in the infrared-wavelengths... Not that the camera is bad or anything, but don't take the actual temperature readings as absolutely correct values. For example, to actually see if the battery or mosfets in your wheel are actually running very hot (at least relative to their surroundings), you'd need to open the compartment so that you can point the camera directly to the board/battery. If just shooting the shell, the part that's over the board compartment could look warmer than the rest, but won't give you that much indication, and the shell plastic itself might reflect at least some heat from the surroundings.
  4. Umm, did I understand correctly, you take in an InMotion and give discount for a Solowheel Glide? Isn't Glide the rebranded InMotion? Also, "perfect for anyone with an entry-level wheel looking to upgrade", and then you only take in big name brands? A Gotway is hardly "entry level" (well, maybe something like the older MCM2's and such), a Solowheel Classic might be... That aside, yeah, it's not a bad idea if you've got some of the cheapest models or a more older (needing battery replacement) wheel, but for anything newer/higher-end model from said brands, the owner would likely get a far better price (and in real money, not "store credit/discount") just by selling it as second hand.
  5. Roll the wheel gently on its side on a carpet or something soft to see which points hit the surface first. Of course that only covers flat surfaces, a protruding rock or such could still hit an unprotected point "in the wild". I did this with the Firewheel, but didn't bother with the KS16S and just slapped some foam on the corners Compared to the KS16S padding I did...
  6. New Lower Pricing For Glide Series

    Wasn't Inmotion Korean? Although I wouldn't be too surprised if the wheels are actually made in China...
  7. Except for one little thing: how do you measure when the battery is full or empty, if the voltage change across the charge state is very small (maybe smaller than voltage drop caused by high current draw over the internal resistance)?
  8. Electrochemical stuff... goes way above my head really. Like Chriull said, the voltage difference is due to different chemistry. But those "conventional" 1.5V alkalines don't go to 0V either, I think they die somewhere around 1V or somewhat below. Trying to pull current from them at that point will just drop the voltage further, but you really get no useable power out anymore. I never got further than reading about galvanic pairs and the potential difference (ie. galvanic cell voltage) of different metals:
  9. Headache

    Just spent a couple of hours on and off trying to find what's wrong with my half-bridges... My head hurts, but I finally found 2 missing wires and one misplaced resistor in total, that caused the 2nd bridge high-side not to open. Oscilloscope and signal generator would be nice, had to go with nothing but cheap multimeter and 555-timer circuit to produce 25kHz square(ish) PWM. Yeah, nobody probably cares, but I just had to vent a bit Now, I still need to build a 3rd similar half-bridge before I can try to drive a motor...
  10. Headache

    I haven't played around much with it, but other than the FLIR-camera, it seems plenty fast and the battery should last a good while between recharges, but I can't really tell yet, because I've only had it for a day. The industrial look is nice, and clearly it's directed to people like construction workers etc, as it should withstand a 6-foot drop to concrete, and 2m/7 feet submersion for a while (5m/16 feet up to one hour when the small switches in front are turned to the "5m"-position, which seal speaker and microphone etc. holes) as well as the military specification demands for dust/shock/etc. -proofness, not that I have tested dropping or submersing it, nor do I plan to. Figured it should last better than most phones at least They're not very common really. The upsides are the low cost vs. other types of heating (at least when installed during construction ) and they actually do work, most people think that heat only goes up, but these work by radiation, not convection (warm air does go "up", or actually above cooler/denser air/gas, radiated heat doesn't care about gravity or buoyancy or such). On a cold day you can actually feel that it's (somewhat) colder under tables and such, as the radiation comes from above. Illogically, normal "radiators" actually work more through convection (warming air that then rises up and out from the radiator) rather than radiation, and that's why they're placed low on the walls. They're completely maintenance free, until they break down. The element itself is just a "film" or a prebuilt-panel with heat resistor wire, but over time as the wires contract and expands with temperature, they'll break. Since the wood paneling or sheets or whatever is used on the ceiling surface material is usually nailed shut, the only ways to get to the panel are either by tearing down the ceiling or trying to reach it from above, but that's not that good here either really, as there's so much insulation in-between (2 x 50mm insulation sheets + plastic sheet to prevent humid air from rising out and condensing, and 400mm of rockwool on top of that) and the attic flooring joists run perpendicularly a good 40cm above them... Like said before, I doubt I'll even try to replace them, instead just switch to radiators once the rest of the elements start to die. The panels that are broken might have been for who knows how long without anyone really noticing, they've been in place for over 30 years. The only place that's clearly colder (around 18...19 degrees C when it's cold) is the bedroom, as both heating panels there are gone and there's nothing else heating it up, except warm air coming through the forced ventilation system and through open door. I was expecting to find at least a few dead panels, so no surprise here. I'd be a lot more worried if the heating wires inside the floor concrete slab would have been broken, as replacing those is hard (tear off all floor tiling, jackhammer the slab, remove old cables, install new ones...)
  11. Headache

    The year changed, and the maximum price for a company phone went up... We get to pick our phones once every two years, so I waited over so I could order the Cat S60, a rugged mil-spec phone with dual processors, 3800mAh battery (which for EUC-people sounds ridiculously small, but is actually about 2-3 times larger than most phones), IP68-rating and... FLIR thermal camera. The camera is the same spec as the Flir One (not Flir One Pro) -module sold separately for Androids and iPhones. The more detailed specs of the phone are in https://www.gsmarena.com/cat_s60-7928.php The image is actually composed by taking a picture from the "normal" camera, doing an edge detection to get details, and then laying a smoothed image from the 80x60 -resolution thermal camera (or at least that's my guess, I didn't bother to look up if that's true, but that's what it looks like... ). In the phone FLIR-software, you can slide the image between the normal camera image and the superimposed thermal image, but I don't know if it can be exported in a GIF-animation or anything. Also, at least so far I wasn't able to find an option for showing the thermal range in the taken picture, but it's visible while using the camera. Also recording videos is possible (probably with a very low framerate), but I didn't try it yet. What the pictures show is our "genius" heating system, a true marvel of the 20th century: ceiling heating. I pushed the temperatures up to see them (although it might seem more extreme looking at the colors, the hottest spots are about 28 degrees Celcius / 82 Fahrenheit, if memory serves). Actually, in the above picture, there should be one more heating panel near the windows. Broken. There should be one in the first picture way at the back. Gone. Only way to replace them is to tear the entire ceiling open, but I'll think I just put on normal electric radiators on the walls when enough of them have come to the end of their lifespan. My study, there should be another panel near the window. Nope, not heating up. In total, out of the 16 panels, 7 are broken. But there's also a heat pump, floor heating in the sauna, bathrooms, "fireplace room" (I don't know the English name for that, "takkahuone") and hallway, and fireplaces, so it's not like we're going to freeze over. Also explains why the bedroom is colder than the rest of the house: both of the heating panels are broken. Take a wild guess which is the fuse for the ceiling heating...
  12. Ninebot One P battery failure & crash

    Nice to have you back on board! I went wheel-less for the summer of 2016 and bought a KS16S last spring. At the same time, I got a good deal on a second hand KS16B, so I actually now have two (working) wheels, but as usual, the riding season here is only from about the end of April until early October or so... There's a ton of application notes on issues and properly paralleling power mosfets, like mismatches between the RDS, Vth and capacitances, as even devices from the same batch will have some manufacturing spread. This can lead to one of the other taking the brunt of the load, as one turns on /shuts off earlier and such, but one of the big issues seems to be high-frequency parasitic oscillation or "gate ringing" if the gates are connected directly: Parasitic oscillation frequencies are typically in the range of 50MHz to 250MHz. Such an oscillation condition is unacceptable because it can cause over-voltage transients on the gate, radio frequency noise emission, high switching losses, and can even lead to uncontrolled, sustained oscillation and destruction of one or more devices. Still, since boards aren't blowing left and right all the time, it may not be that big of an issue with the wheels. The problem is, if the oscillation is there, it may be able to push the gate voltage above the maximum, breaking the gate, or drop it low enough for the mosfets to enter the linear region, where it starts to limit the current. At the same time, the inductance of the motor likely tries to keep the current flowing, raising the voltage at the drain and keeping a high current flowing through only partially conducting mosfet, leading to a very high power dissipation and sooner or later destroying the device. At least on the dead ACM-board I inspected, the gates were just directly tied to each other, with no resistors or such in-between. But that one had fried the MCU-side, so I guess it still works just fine, at least most of the time. For the spot-welder above, I used ferrite beads in series with gate resistors and parallel reversed diode (to speed up shutdown), along with a gate driver capable of up to 12A source/sink driving all the mosfets. Effectively I stole the design from the Firewheel gate drives as I was reverse-engineering their board, but hey, it worked good I doubt I "know much more about the details", I usually just pick from whatever I have (except for the spot-welder, which is the only really high-current device I've built, there I ordered the mosfets specifically), picking something that has typically a much (like, say, 2-4 times) higher theoretical maximum current than what I think I'll need. Then work out the expected power dissipation and junction temperature rise with highly exaggerated thermal resistances (Trying to figure out the thermal resistances can be a pain, so for me it's pretty much a guessing game). For other values, if I need fast switching or whatever, I look up some equations and try to calculate some back-of-the-envelope rough values, and do a bunch of simulations in LTSpice, then just built the damn thing and see if it works Usually my devices are so low currents (few amps at best) that almost anything works Not very scientific, but so far I haven't managed to destroy a mosfet in my own designs through overcurrent/-heating, but just blew a motor speed controller mosfet through static discharge a while back Lizardmech, who is on a whole another level in electronics design, pointed out the poor design of the Ninebot boards earlier: What is weird that they don't even use pre-made gate drivers, but instead built their own from discrete components Also, although that's not a P-board, he points out that the resistors can have very high power dissipation, which I guess your destroyed board shows. More mosfets in parallel certainly should help with the power dissipation per device, assuming the issues that come with paralleling are correctly taken into account. Many of the wheels might actually be suspectible to the paralleling issues, but those might only come out in very specific scenarios. Trying to figure out what exactly killed a mosfet afterwards can be pretty hard, as there's so many ways for them to get destroyed, but when operated within the "safe" values, they should generally be pretty robust. Generally the burned mosfets seem to occur with high transient currents (trying to get going from standstill over a curb or something similar) and plain overheating. I'd expect that the Ninebot-engineers would have tested and checked that there's low enough thermal resistance for the heat to conduct off fast enough with single mosfets, but apparently something went wrong. The whole P-fiasco and the firmware updates that bricked a number of E+'s still overshadow Ninebot... The Z-series looks good, but I have my doubts. BTW, the 1200W nominal KS16S uses only 6 mosfets, but they're TO-247 -packaged and very low resistance: https://www.infineon.com/dgdl/irfp4368pbf.pdf?fileId=5546d462533600a40153562c61512015 I haven't torn my own apart to see how the gate drive is made, and haven't followed closely on the forums to see if anyone else has torn their down. Gotways use IRFB4110 and IRFP4110 (same Mosfet, I think, expect one is TO-220 and the other is TO-247), in paralleled configurations. I think there have been some blown mosfets there, but haven't followed that much on it. The failures seem to have moved more from mosfets to inadequately sized motor cabling melting, hall-sensor issues and otherwise broken boards. There haven't been that many lately, but if you've got over a year of catch up, then it might take a while... I haven't actually been that active in about a year or so, I've given up on trying to read everything in the forums long ago, and just read here and there randomly. Noticing that you were back was a bit of a fluke, could have gone undetected for much longer
  13. Headache

    Not much has happened since returning the final report. While changing from remote working to actually having to go to an office every day has been a more welcome change, the downside is that it leaves me with lot less free time, and after the final squeeze on the course, I didn't want to do much anything for a couple of weeks. I did work on a couple of pedal designs (and actually do have some simulations made for a simple pedal a friend wanted me to make) around the holidays and last night finally managed to work out the fault and fix the CNC motor speed controller. Not that it was that hard, as expected, the mosfet controlling the motor speed had failed, but getting the controller out, ensuring that the problem was with the mosfet and replacing it, adding protections to prevent it in the future and then putting the entire machine back together seemed more like a chore, although it didn't take but a few hours I already mentioned the bulk of the issue in another topic, so I'll just copy-paste it here: A couple of months back, I destroyed my DIY motor driver in my CNC by static electricity. I milled, drilled & cut more than 50 different PCB designs, some more than one piece, on that same controller without any problems. When it failed, I was changing the bit, which I do a minimum of 2 times (if there are no holes to drill in the PCB) per board, usually more times (at least 1 for milling, 1 for cut out, and the amount of different sized drill holes) and always in a similar way (two spanners to release & tighten the ER-11 collet). When I touched a spanner onto the collet of the motor, suddenly the motor started running at full speed. The viable explanations are that it was a high voltage static discharge causing either an avalanche breakdown or high dV/dT (voltage change over time) -spike, do note that the part was connected to the drain of an N-channel mosfet, not the gate (which can only withstand +-25V difference to source, usually +-20V, but this mosfet is a bit "unusual" in that sense) or source. Both the gate and the drain-source -channel were destroyed (20 ohm resistance from drain to source, 36 ohms from gate to source), leaving the mosfet open at all times. Just last night I replaced the broken mosfet and the controller is running happily again. Also added some transient voltage suppressor diodes to prevent this from ever happening again. The original circuitry already had some protections in place: The mosfet is a Fairchild FQP30N06, rated for 60V VDS , 21.3-30A continuous and 120A pulse current, and +-25V gate voltage. There's a TVS-diode across the motor connector (don't remember the voltage though and it's not marked in the schematic, 30V?), as well as 10A -rated freewheeling diode for negative spikes, but still the fet was destroyed by a static discharge, likely as the voltage against ground went to very high value. The 15V zener on the gate-side has a forward resistor so it wouldn't get destroyed, but that's a design fault. There shouldn't be a resistor in front of the zener, as it will allow the gate voltage to stay higher than the zener reverse drop, essentially NOT protecting the gate from transients. In this case the voltage spike occurred at the drain, coming from the motor connector (P_SP_PWR_OUT1) and reading through the mosfet failures, the likely candidate is a high dV/dt -spike that destroyed the gate insulation, leaving the mosfet open, regardless of whether there was any voltage at the gate or not: The cause of this failure is a very high voltage, very fast transient spike (which may be positive or negative going). If such a spike gets onto the drain of a MOSFET, it gets coupled through the MOSFETs internal capacitance to the gate. If enough energy gets coupled, the voltage on the gate rises above the maximum allowable level – and the MOSFET dies instantaneously. The process less than a nano-second! The initial spike destroys the gate-body insulation, so that the gate is connected to the body. Once that has happened, the MOSFET explodes in a cloud of flame and black smoke. We have one documented case where the battery wire worked loose, causing a spark. It must have been this that caused the gate breakdown for the explosion of flame and smoke did not happen until the battery wire was re-connected some time later! Which demonstrates how very difficult cause and effect can be to connect! In my case, the mosfet didn't explode (there were no outside signs of damage), but was definitely destroyed. To make the controller more robust against such incident in the future, I've added a 30V TVS-diode (unidirectional, as I didn't have any bi-directionals above 20V, but it won't matter much there) in parallel with the fet, and another 15V bidirectional TVS going from the gate to source (well, in this case, ground). I should now be able to get back on track with making boards, but I still haven't designed any since the robot. Currently, I'm looking into making some ATX-breakouts (for using computer ATX-power supplies in more projects), a DC load (mostly just an issue of finding a suitably large heat sink, the circuitry itself is very straightforward) and prototyping the pedal for a friend. In other unfinished projects, there's (still) the charging circuitry and controller for the spot-welder, and the robot software... I'm getting sort of cold feet with the idea of spot-welding lithium-cells with homemade equipment, and right now writing software outside of work doesn't seem that tempting And there's always the time vs. energy -stuff getting in the way, the downside on working with electronics- and software-hobby projects is that (at least for me) it's hard to get anything done in so small parts that I could only do an hour here and there, instead I'd need at least 4-6 hours straight, preferably an entire day without distractions, and only after a good night sleep (either of which I haven't had lately). Trying to do any designing or writing code after a full work day is usually impossible, although software engineering is just "sitting around and typing", it's pretty exhausting mentally, especially with tight deadlines.
  14. Adjusting charger's voltage

    I could be wrong, but I've assumed that the "cutoff"-setting in the wheel chargers only triggers the (usually) red/green-LED for showing charging/ready. At least my Charge Doctors (sitting between the charger and the charging port, so measuring the output from the charger to the battery) have always showed that there's still current going into the battery after the led turns green, and I've run it down to showing 0.00A (they only show down to tens of milliamps), which takes quite a long time, but would seem to indicate that the charger keeps putting out current until disconnected (either from the wall plug or the charge port) or until the battery stops drawing current entirely. Of course different chargers could work differently. As far as I can tell (without dismantling an entire charger, doing measurements and going through the trouble of figuring out the entire circuit etc), the chargers seem to always internally have the set voltage you can measure from the output connector (like 67.2V for example). After the constant voltage -section of the circuitry, there's likely another section that handles the constant current-part, that is, there's a part in the charger that drops some of the voltage so that the current can never rise above the set limit. What supports this theory is that chargers with fans have the fan running during most of the charging (more voltage being dropped internally in the charger -> more power dissipation in the charger needing cooling), but the fan stops once the charging nears completion. It could be as simple as a low-side constant current source (well, actually, constant current sink), with a comparator for turning the red/green leds on and off depending on voltage drop over a sensing resistor. Not sure why in your case the charger output would never drop below 30mA. Maybe the BMS keeps drawing power for whatever reason after the cells are already completely full, or has that much leakage in the charging-side of the circuitry?
  15. Ninebot One P battery failure & crash

    Suddenly, @Cranium! You disappeared for a good, what, 1.5 years? Sorry for your troubles with the Ninebot, I thought that all the P's were already buried somewhere deep and forgotten. As for the power dissipation and maximum current numbers of the mosfets, I was lazy and just copied an old post of mine: The numbers in the datasheet are purely theoretical, usually assuming an "infinite heatsink" and such. They do have their uses in the sense that since (more or less) every manufacturer uses the same way of reporting those values, you can compare the values between mosfets, but you should never assume you can go that high in real life circumstances. This quote from Olin Lathrop in electronics.stackexchange.com sums it up pretty good: Yup, that's the way MOSFET datasheets work. The maximum current rating really means "This is the maximum current you can ever possibly get thru this thing, if you were to somehow not violate other specs in the process, although we have no idea how to do that. We put this here because we think it's cool, and maybe someone is dumb enough to buy a truckload of them before realizing they can't actually run the part at this value for any set of real world conditions." Basically, each of the limits of the device are specified separately. You have to look at what you're doing and carefully check each one. The real limit on current is usually die temperature. To check that, look at the max Rdson for your gate drive level, compute the dissipation due to your current, multiply that by the die to ambient thermal resistance, add that to your ambient temperature, and compare the result to the maximum die operating temperature. When you figure all this backwards to find the maximum current the device can take before overheating, you'll usually find that's well below the absolute maximum current spec. (from http://electronics.stackexchange.com/a/216944/128374 ) If you dig the mosfet datasheets deeper, you will find a graph showing the "safe operating area" (SOA) under different conditions, but even there the case (package) is usually assumed to be at 25 degrees C, and should be derated further according to how hot it is expected to go (as well as taking a lot of other limitations and characteristics into account, that's why there are so many numbers and graphs in the sheets). This is from IRFP4368, used in new KS16S's. Note that it says Tc = 25 (case temperature) and Tj = 175 (junction temperature). The reason for using 6 mosfets instead of 12 could be that the new ones were seen as "good enough" to use without paralleling... but that's just guessing. I've learned that slapping mosfets in parallel just by tying the gates together is a bad practice. It may work just fine, at least for a while, but there are more proper ways to do it, so that the slight variations in the gate characteristics (such as Vth and capacitances) don't cause havoc like gate oscillation. Here's 5 "properly" paralleled mosfets delivering >1000A / >10kW pulse for your amusement:
  16. Another new Kingsong (16S) Owner

    There's quite a long list of things that can cause a MOSfet to fail: https://www.4qd.co.uk/docs/mosfet-failure-mechanisms/ https://sites.google.com/site/scidiy/diy-electro/mosfet-s-and-how-they-can-fail Not sure if these even cover everything, a common way to kill a mosfet is overheating or overvoltage on the gate. A couple of months back, I destroyed my DIY motor driver in my CNC by static electricity. I milled, drilled & cut more than 50 different PCB designs, some more than one piece, on that same controller without any problems. When it failed, I was changing the bit, which I do a minimum of 2 times (if there are no holes to drill in the PCB) per board, usually more times (at least 1 for milling, 1 for cut out, and the amount of different sized drill holes) and always in a similar way (two spanners to release & tighten the ER-11 collet). When I touched a spanner onto the collet of the motor, suddenly the motor started running at full speed. The viable explanations are that it was a high voltage static discharge causing either an avalanche breakdown or high dV/dT (voltage change over time) -spike, do note that the part was connected to the drain of an N-channel mosfet, not the gate (which can only withstand +-25V difference to source, usually +-20V, but this mosfet is a bit "unusual" in that sense) or source. Both the gate and the drain-source -channel were destroyed (20 ohm resistance from drain to source, 36 ohms from gate to source), leaving the mosfet open at all times. Just last night I replaced the broken mosfet and the controller is running happily again. Also added some transient voltage suppressor diodes to prevent this from ever happening again. I don't recall seeing TVS-diodes in wheel boards though. Cost cutting? I'd expect that the high(er) voltage motors could (in rare cases) cause large enough spikes to toast a mosfet... How this actually relates to EUC Extreme's wheel is a bit lax, it's possible that when the motor cannot turn and high current runs in a spike through it, the inductance could cause a high enough voltage transient to destroy things. But of course, there are many other failure modes too...
  17. Another new Kingsong (16S) Owner

    This is somewhat low amount of samples and only accounts for about half of last year (Feb-July 2017), but I think it does give some indication of failure rates: Here there is a full percentage of marriage for any service call due to electronic or electrical problems (here, mechanical damages and tire punctures are not taken into account)The percentage of rejects from sold devices during the period February-July 2017 is indicated. In brackets, my comments are highlighted by a frame. P.S. The recall company for Gotway is not included. Therefore, statistics on the Got are slightly larger in reality. Inmotin: V8 - 4.8% (excellent quality: wow :, there were a lot of sales) V5, +, F - 5.88% V3c, pro, s - 7.8% KingSong KS14B - 3.33% KS14C - 15% (due to low sales, as the model changed to 14d) KS14D - was not in the service (selling was enough) KS16 - 7.33% KS16S - 1.12% KS18 - 17,24% (transition to sports) KS18S - was not in the service (sales were moderate) GotWay MCM4 - 18.57% ACM 680,820 - 36,6% ACM 1300 - 35% (a small number of sales, according to my personal feelings this is the best of the gothweb) Msuper 680,820 - 11,11% (the average number of sales, here statistics is more visible) Msuper 1600 - 36.98% (every 3 users of a pregnant soup met in the service, the statistics could be a little lower, because in my memory there were repeated calls for the same problem) Monster - 23.4% (a small number of sales) 2. And here now I will show the statistics of the marriage in percent only on the controllers and sensors of the hall. Inmotin: V8 - 1,97% (the standard, as I already said) V5, +, F - 2.71% V3c, pro, s - 2,12% KingSong KS14B - 2% (reference wheel standard) KS14C - 10% KS14D - was not in the service (selling was enough) KS16 - 3,33% (the percentage of the marriage is halved due to the fuse on the board) KS16S - 1.12% (reference) KS18 - 6.89% (the percentage of rejects decreased threefold, 18 of the usual words had problems with the charging connectors and balancing the battery) KS18S - was not in the service (sales were moderate) GotWay MCM4 - 14.28% ACM 680,820 - 26,6% ACM 1300 - 14.28% (all problems are of the same type - controllers or hall sensors) Msuper 680,820 - 9,25% Msuper 1600 - 34,24% (every 3 users of a pregnant soup met in the service, the statistics could be a little lower, since in my memory there were repeated calls for the same problem) Monster - 23.4% (a small number of sales) Final output: Let's break our conclusion by brands. - Inmotion is very good with the quality of monocols and this statistics confirms this. Sales were many and the statistics complete. Inmotion keep it up, there is much to grow. But in general. Well done. - KingSong - the average percentage of rejects for old models (14c, 16 and 18). And the phenominal results for the new sports versions. I also want to note separately 14B - the best wheel for entering the monocoque tusovka in relation to quality. You pay a little, you drive sadly, but not in service: laugh:: laugh:: laugh: - Gotway - it's bad ... We need to work on quality. No model can compete in quality with either kingsong or inmoshenom. There are weak attempts at Msuper680, 820, but not enough. Msuper1600 - generally horror. 84B and the controller from gothve is a nuclear device. As I have already written many times - buying goths makes sense only when you understand what you are taking. Exceptionally speed. If you are not about the actress, unfortunately, goths should not be considered. I very much hope that the gothwa will draw its quality to the level of the standard set by Inmotion and KingSong. P.S. If you have something else to count or see - ask questions in the topic - I will try to find answers to them. Since October 2017, we will have a new program for recording faults and everything will be much better and clearer in it.
  18. "Poorly Made In China: An insider's account of the China production game" is a book by Paul Midler, who has lived most of the current century in China, acting as a "middle man" (consultant/advisor) mostly between foreign importers looking to get products made cheaply in China and the local companies and factories producing them. Midler has both the business-side education and ability to speak fluent Mandarin, so he's seen and heard quite a lot. Now, I knew that Chinese products get a lot of bad rap, but can it really be that bad? Midler certainly isn't wearing any silk gloves when writing about the industry. Forget about sweatshops and tired, poorly educated workers, a lot of the "quality fade" is deliberate and planned, sometimes even as the first orders are being made. A factory can start production fast and according to your specifications at nearly zero margins (of course you won't know that), and make an ok-product (at start), as they bet they can make up for it in the longer run by cheapening the manufacturing costs through many (often quality-related) changes, ranging from using less materials to outright changing them to completely other, cheaper and poorer quality ones, even toxic, without any notification or warning. And then running bootleg-operations selling copies of your products to other channels (possibly directly past you to your customers) and hiking up the price based on a poorly justified reasons, preferably at a point in time when you're not in a position to refuse. You thought you had agreed on a price for that order you'll need to be forwarding to your customers in a couple of weeks? "You heard me wrong!" The book's already a bit dated (the first edition came out in 2009, this revised edition was published in 2011, and the events depicted have happened somewhere between 2002 and 2008 or so), so maybe (one can hope) things are a bit better than about a decade ago. Most of the book is centered around a specific customer case, that of Johnson Carter, an American importing company looking to get liquid soap and shampoo made cheaply in China for selling onwards to dollar stores and such, and King Chemical, the factory that they start working with, and the years following. There are a few others stories too, but not that many. Midler says that they were picked for their entertainment value, but give a good representation of what's it like to conduct business in China, and the troubles most companies likely will run into. Of course, although the stories are real, the actual names of the companies and people involved are made up, for obvious reasons. And while Midler says that he's not a professional writer, in my opinion the stories and the entire book is well written and knit together, all the while drawing parallels in the way the business is conducted to Chinese politics, culture, history and traditions. I couldn't help but be amused (and horrified, thinking how many poorly made in China -products I have here, especially eletronic and electric devices... time to check the fire extinguishers? ) as the stories unfolded. I think this could almost as well be a comedic (or even farcical) novel than a depiction of real world events. Then again, I know next to nothing about running a business, even less in a Chinese business culture. I just finished reading the book, reading through it in two sittings (well, it's only about 240 pages) and I'd suggest that everyone even considering of starting an import business from China should definitely read it. Even if you don't, it's still a good read, just for the entertainment value. You'll never look the same at all the Chinese products you have and buy Granted that companies like King Song, Gotway or other "big name" Chinese EUC manufacturers are different, in the sense that they actually have their own products, rather than just being a manufacturer to specifications from a customer. Big companies that make things like TVs and smart phones have the ability to keep the quality control in check and prevent (most) big failures and scandals. But there are things in the book which could easily explain the horrible quality of hoverboards during the biggest craze. Still, I can't help but wonder how much these kind of tactics are used in the EUC-industry too. Maybe @Jason McNeil can shed light into this, if you ever get around to read the book?
  19. Pari pyörää käytettynä Suomesta ja yksi Briteistä, uutena KS16S Saksasta 1RadWerkstatt:lta. Halvempaa kuin Suomesta, mutta varmasti ei pärjää hinnoille joita voi saada suoraan Kiinasta tilaamalla, lähinnä halusin varmistaa että takuu pelaa jos tulee ongelmia, eikä hintakaan nyt niin paha ollut.
  20. FET Voltage ratings of 84V versus 67 volt wheels?

    You likely got your answer already from elsewhere in the forums, but from what I know, the Gotways use IRFB4110 (TO-220) and IRFP4110 (TO-247): https://www.infineon.com/dgdl/irfb4110pbf.pdf?fileId=5546d462533600a401535615a9571e0b https://www.infineon.com/dgdl/irfp4110pbf.pdf?fileId=5546d462533600a4015356290ec51ffe Both are 100V, and (I think) pretty identical, except the TO-247 can of course shed heat better due to larger case. KS16S uses IRFP4368, 75V, TO-247: https://www.infineon.com/dgdl/irfp4368pbf.pdf?fileId=5546d462533600a40153562c61512015
  21. NOTICE: Recall for GOTWAY MTen3 (Green Fashion)

    I thought the issue with Gotways nowadays is mostly the wiring and such... Had a brief exchange with EUC Extreme tonight, here's a rough translation of what he had to say: "The Gotway mainboards break way too easily. I'm tired of constantly exchanging them. On top of that, they can't deliver the correct boards that work with the motors, it causes constant grief. I don't understand how it can be so hard. Apparently they're changing everything so often, that they don't know what board fits to which wheel themselves." I think he was referring to V3 though. Original text in Finnish, for the very few here that understand it: "Gotwayn piirilevy on aivan liian herkästi hajoavaa mallia. Oon kyllästyny vaihtelemaan niitä jatkuvasti. Vielä kun he eivät saa toimitettua oikeanlaisia piirejä moottoriin sopivaksi, aiheuttaa hermojen menetystä oikein urakalla. En käsitä miten se on niin vaikeaa. Ilmeisesti he muuttaa kaikkea mahdollista niin usein, etteivät tiedä itekkää mikä enää sopii mihinkäkin."
  22. firewheel charger needed

    I believe it could very well be just left behind, it's not really an expensive wheel these days and if flying, you can't take it with you. The wheel's very "old" by this day standards (circa 2014), has the notorious "overspeed"-shutdown problem unless the packs are shunted (might be fixed in later mainboard revisions?), lots of burned boards in the earlier ones (not mosfets, usually the step-down circuitry fried, possibly taking the MCU with it, but if it doesn't happen in about a month, it likely won't happen) and is not that powerful (550W nominal). Not that it's a bad wheel still, I loved riding mine (second-hand F260), just that safety-wise, the thing's a deathtrap, and power-wise not suitable for higher weight riders (I had no problem going above 30km/h on mine with shunted packs, only 2P!). https://fire-wheel.eu/en/ is a French company selling the (last?) Firewheels from their inventory with -50% prices, 520,50€ for the F528-model (528Wh) and 644,40€ for F779 (really 680Wh) for new ones, so it's not that expensive really. The R-line is even cheaper, but I think they only have the "Comfortable"-mode, which is really way too soft... at least in my opinion. I think the company who made them (don't remember the name anymore) went bust around 2015/2016?
  23. firewheel charger needed

    "Standard" 67.2V charger with GX16-3 -connector should be fine... I've charged mine both with the original and an old Gotway-charger (from MCM2s, I think).
  24. Ultracapacitors vs li-ion battery

    Yup, electricity is relatively cheap (around 10 euro-cents per kWh), and "filling" a wheel doesn't take up much (maybe around 1kWh for the 840Wh KS batteries with the losses of the charger, and that can transport me a good 50+km). At least compared to usual consumption in a mostly electrically heated house and Finnish winter: Those are our daily usages in kWh (kilowatthours) with the outside temperature laid on top, and last winter wasn't even that cold (and summer wasn't that warm). On a cold winter, it usually tops above 100kWh at least for a few days, and close to it for about a month. Solar power? Sure, but the last offer I got, the system installed wouldn't have paid itself off over its lifetime after calculating the production with a bit more realistic values than the optimistic ones given by the company. There's about 3-4 months in the year that the power usage is at its highest, and at the same, it's so dark all the time that the solar power system doesn't provide much anything. Had to check, the winter of 2016 was much colder (or should we say "more usual"):
  25. There's an app you say?

    That's actually the real Gotway site Or "Guangzhou Kebye Electronic Technology Co.,Ltd"