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esaj last won the day on July 2 2017

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About esaj

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  1. 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...
  2. 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.
  3. 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.
  4. 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...
  5. 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...
  6. 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)?
  7. 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:
  8. 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...)
  9. 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...
  10. 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
  11. 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.
  12. 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?
  13. 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:
  14. 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...
  15. 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.