Chriull

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Chriull last won the day on December 3 2016

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  1. I tend to believe to people from http://batteryuniversity.com/learn/article/serial_and_parallel_battery_configurations (plus some other articles there mentioning this possible incidents in more detail - just did not find them again by scanning the index...) - my own knowledge or experience about this details are not really existing
  2. Seems to be the explanation for the loud high pitched noise gotways and kingsongs produce compared to other wheels... Either they use an BLDC instead of an PMSM motor or they just have a non optimal/?wrong? driving algorithm. I came more or less to this assumption from browsing http://krex.k-state.edu/dspace/handle/2097/1507 - but i never could read this in detail Thanks for citing this nice summary! Sorry for the off topic input from my side
  3. The motor should have no direct prob by a 25% higher voltage. The primary danger from higher voltage would be "breakdown voltage/disruptive discharge voltage" of the insulation of the motor coils. Insulations are designed with much higer safety factors. By the higher voltage the motor could just be destroyed since by the higher possible currents it could be "overpowered" (overtemperature, demagnetizaton of the permanent magnets, magnetic saturation, etc) which still seems to be well within the possibilities of the motor. Its a quite solid metall part with nice cooling (air contact). Additionally, as frequently reported, the motor wires, connectors, mosfets, etc are designed to act as fuses to protect the motor... ;( Edit: At low speeds the mainboard limits the possible max current anyway - so since with the same max current one gets the same max torque the battery voltage does not (really) matter. For speeds this current limiting is not in effect anymore (torque resulting from this max current is outside of the max torque speed limit) the max torque speed limit curve is in favour of to the higher voltage EUC. -> higher speed and higher torque at the same speed possible (if the electronics and wires survive it;) ). Edit2: @Rehab1: Mentioning a voltage regulator is a nice way to describe how the EUC controller works - the controller chops the battery voltage into pulses of different duty factors. The inductance of the motor coils (by the mechanical ?inertia? (load) of the system) smoothes this pulses to the average of this chopped voltage. So there exists a voltage converter in every EUC. i.e. no matter if looking at the 67,2V or 84V version of this wheel with the same motor - if they drive side by side with the same speed and acceleration and the same resistance forces (wind, incline, riders weight, balancing, etc) the controllers of both wheels generate the same averaged voltage for the motor.
  4. Parallel connection is by far not as critical in regard to cell specifications as series configuration of cells. However If different cells are directly paralleled as worst case the weaker cell deteriorates until it could be pushed by the stronger cells to reverse polarity -> desaster Also nicely selected cells deteriorate differently and can end in the same desaster... For paralleling cells with different specifications it's best to build packs of this different cells and parallel the whole packs and not every single cell. The higher capacity cells should in such a configuration be able to nominaly deliver more current (?imho direct proportional to the capacities?) Unfortionately not to detailed sources in regard to this topic: http://batteryuniversity.com/learn/article/bu_803a_cell_mismatch_balancing http://batteryuniversity.com/learn/article/serial_and_parallel_battery_configurations
  5. Reasons for a BMS that come into my mind: - also nicely selected cells can drift apart after time - Without a BMS there is no cell balancing happening to prevent any potential drift (as for RC modells cells without BMS (no "internal balancing") are commonly used, there the charger does the balancing (needs 'number of cells in serie + 1' extra cables + 2 charge wires), which can lead to major degradation of the batterie pack. If i remember correctly especially in high load situations in cold weather (imho somewhere described in http://batteryuniversity.com/learn/) - The BMS shuts down in case of a short-circuit (bridge shoot through, wheel/motor stuck, current limiting at low speed does not work correctly, motor cable insulation melted -> short circuit). Without a BMS vast amounts of energy could be set free in such a short-circuit case. On the other side in http://forum.electricunicycle.org/topic/459-electric-unicycles-bms-problem-and-solution/ for example many users have the opinion, that any over current shutdown by the BMS is bad and should be disabled - better the rare case of overheat/fire from shorted batteries than an accident caused by shut-down. Another shut-off condition of most/all BMS used for EUC is over-voltage while regenerative breaking. Batteries: Nominal Capacity and max nominal/peak current allowed is only one part of the picture that shows the characteristics of an cell. For low capacity packs (2p for example) such "high performance" cells could be of advantage since they are able to deliver needed peak power. For higher capacity packs (more cells in parallel - not as much peak current per cell needed) lower nominal capacity cells with lower max nominal/peak performance could be advantegous. "High performance" cell tend to deliver much less than the nominal capacity at same currents than some "low perfomance" cells. So for a 6p battery pack a 10A 2900mAh pack could deliver a much higher "real world" performance than a 30A 3.500 mAh pack (fully fictional example without any investigation).
  6. Hi, I moved you topic to Gotway since you accidently posted it in the Inmotion section... Google Translate: "Hello how can i check the voltage of my acm16 84v in the application i see less 62 .. 100% battery my version can not have 84" In which application? The original version? Imho there were already some discussions, that the 84V Versions only show the 62V in the app. I did not really follow them - i just remember that this is/was the normal behaviour and only an display error from (?some?) apps... But i am sure some experienced Gotway riders can give you more details! Otherwise if you know how to open the ACM and have a multimeter you can just measure the battery voltage. Before you can measure the output voltage of your charger.
  7. The price is very nice - new ones sold starting from ~1000 EUR, actually found them being sold ~899EUR, some shops offered them inbetween to clear their stocks for ~500-600 USD. It is definitely not. Also not IP65 (as they claimed in the beginning). Maybe the solowheels, as @Hunka Hunka Burning Lovementioned. But solowheels are imho overpriced and underpowered... Imho the last releases Solowheel is do old to have some UL-2272 certificate, or did i miss one? Another chance for UL-2272 could be the newer Ninebot S2 and the Inmotion EWheels. According to @Jason McNeil comparison at https://www.ewheels.com/comparing-segway-ninebot-s1-inmotion-v5f-feature-review/ they have the certificate. Maybe he can approve this? The Ninebot One E+ has imho a quite accurate total milage shown in the app which cannot be reset? Somewhere above 1000-2000 km chances rise that the wheel could be "overused" Easily just by the total milage. To really test them you would need something like the charge doctor from @hobby16 (http://hobby16.neowp.fr/charge-doctor-features/). With such a device you can determine how much charge the battery takes while charging it from as empty as possible to full... As @Hunka Hunka Burning Lovealready stated: The batteries are an array of 18650 cells, but not easy replaceable - they are normally spot welded and messing around with the single cells can lead to quite nasty incidents if one is not experienced. I never used them, but from what is written here they tend to slow down/inhibit the learning process and decrease safety! Wrist, elbow and knee guards are beside the helmet highly recommanded! Especially since unfortionately normal, untrained people tend to land on their knees and wrists once the fall forward ;( So maybe it's not the best idea for you to start driving an EUC with your knee probs? Also you should be prepared to jump off and run a bit, especially in the beginning. Also every unevennes/bump in the road should be compensated by bending the knees. But for just driving on even roads/side-ways on your campus riding an EUC could be a big relief for your knees. Imho here where some positive reports about starting to learn driving with a shopping cart. For me the most difficult thing to learn was getting on the EUC - so i started always near some wall/pole to mount the EUC and also stop near something to unmount the EUC. For me it was also helpfull to split the training sessions in 15-20 minutes units once, twice a day and after one week i dared to drive in public... But since you already mastered pedal powered unicycles you have good chances that you just hop on the wheel and drive - there are many videos around about unicycle riders which drive with an EUC instantly! If the Ninebot One E+ and the batteries are in orderly condition you should have no problem to sell it again at USD 300. Imho.
  8. +1. More exactly current is proportional to the torque which is proportional to the force. The forces to overcome are for acceleration (m*a), air drag, rolling resistance and "height changes". As you already stated, tiltback is just some acceleration to establish the different pedal angle. Some current (power) is needed for this depending on the "speed of this change==acceleration". Depending on the "riders reaction" while this tiltback is established (standing on the toe tips or still balancing his weigt evenly on the pedal) additional power could be needed to "lift" the rider. My post cited again for @Mono resoibse: "I assume that the "rumours/stories/accidents" from faceplanting after tiltback kicked in are not primarily related to the tiltback it self but to too fast acceleration towards cut-off speed. Or also the (small) acceleration needed to tilt-back could be the last bit "needed" to reach the cut-off speed?" Instead of cut-off speed i should have used "max torque-speed limit". Imho cut-off speed is not (easily) reachable while driving. Cut-off speed is normally reached with very low load (like lifting the wheel). While driving/accelerating to higher speeds the wheel has to overcome a much higher load (accelerating the drivers mass, air drag and rolling resistance + balancing) so the max torque speed limit _should_ be reached way before cut-off speed *2). Maybe with extrem acceleration one could hit cut-off speed by the build up momemtum while already "going along the max-torque speed limit" - but this "going along the max-torque speed" limit means that the wheel is already in an unstable state (no balancing possible anymore), so a overlean/faceplant/crash is already unavoidable (for non acrobatic riders *1) and the cut-off by firmware just "triggers" the crash at a little bit lower speeds as it would happen anyway. As @KingSong69and @Slaughthammer stated the tilt-back vs accident discussion are old an ongoing, but imho there are still too much false rumours around and no (for me) satisfying resolution accepted in this forum. So for me this discussions will go on, as long as i see an resolution to be found sometimes, somewhere... So starting with normal tilt-back conditions/situations which never should bear any problem: - Tilt-back comes slowly and nice so it is easily to be recognized by the rider and one can distribute ones weight on the pedals and shift the weight to the heels to decelerate and stop the tilt-back situation: No hard accelerations are happening, so no current spikes, voltage drops, overpower situations can happen and tilt-back does together with the rider what it's intention - warning and deceleration. Any overlean/over-power cut-off happening while this "kind of tilt-back" occurs should be imho just in combination with an sudden incline, bump, wind gust, etc and triggered by this "extra" force needed. The tilt-back just happened at the same point in time but has no correleation with the incident. A situation i do not consider or care about: - People driving with the wheel is in tilt-back state. So the are nearer to the "max-torque speed limit" and every additional power needed (incline, bump, wind gust, imbalance) could lead to an overpower/overlean situation - they took their decision so they should also take the accident. There is nothing more the wheel/firmware could to to warn the rider. So "dangerous" tilt-backs are imho the fast ones, which come within fractions of a second. If they do not throw the driver off the wheel the danger comes from the rider regaining balance on his toe tips leaning forward and by this further accelerating the wheel. In my case shown above in the graph the tilt back pushed me back resulting in a deceleration (negative, regenerative current spike) and i recovered my balance on the toe tips forcing the wheel to accelerate to the second tilt-back stage (~10A current spike), followed by some positive negative current spike (de and acelerations) until a regained balance and normaly decelerated to a safe and stable state. If i would not have lost balance and immediately stayed on my toe tips with the sudden tilt-back happening this situation would have ended in a nasty accident. After my already strong but still sane acceleration (~10-15A on a level road) for a 9Bot E+ my balancing on the toe tips would have increased this acceleration to an not (by the 9Bot) managable overpower situation. With whichever of voltage drop, overpower cut-off, overlean by hitting the "max torque speed limit", etc being the final accident trigger. If in the same situation without loosing the balance one does not balance on the toe tips but immediately stay with slightly more weight on the heels one just decelerates and drive on like nothing happened... That's an acceptable situation for test-drive dummies, beta testers, adrenaline junkies and others who like to live on the edge of disaster - and after some spectacular incidents they should imho learn to manage all this situations. But for customers who just want to drive, have fun and willing to pay good money for this wheels this "fast" tilt-backs are just an irresponsible and not acceptable firmware issue! In my above real world example the first tilt-back stage came within one second (from 26m30 to 26m31) - this does not sound to fast in the first moment, but while accelerating it comes quite surprisingly. So something like ~2-3 seconds should be the absolute minimum for a tilt-back warning. So the tilt-back should have started slowly and nicely at 26m28-26m29 quite immediately after i started my acceleration. So by an soft tilt-back (~1-2°) i would have had to lean even more forward to keep up the acceleration and so noticed that the wheel warns me. Keeping the "original" lean forward would have resulted in a slower acceleration and a safe and nice end-speed with absolutly no surprise or danger... So since the wheel constantly measures the speed and by this can easily compute the acceleration it's an very easy calculation if one would reach the tilt-back speed limit within 2-3 seconds and it's time to start tilt-back nicely! Another fast and dangerous "fast tilt-back" situation i presumably encountered on my 9Bot E+ was once i drove and the battery charge went under a certain threshold which lead to a lower speed limit for tilt-back. So since i was actually driving above this speed limit tilt-back kicked in immediately. This situation could also happen with every wheel that has battery charge depended speed limits. Or also with (over)power, temperature, etc triggered tilt-backs. If in this case the tilt-back comes as hard and powerfull as the wheel can manage it's just again an irresponsible and not acceptable firmware issue - that's easily to program to perform the tilt-back nicely so that it's again a warning the driver can recognize and respond to it without being surprised! The "rear-up" condition reported from @LanghamPi fortunately did not encounter till now, but i remember that there where some posts already about this happening. Could this be some kind of warning triggered by to fast deceleration (regenerative "overpowering", overvoltage warning)? Did you confront Inmotion or your reseller with this strange behaviour? Are there any other "fast and/or dangerous" tilt-back conditions already identified? Would be great if they would be resolved with new firmware updates! Would be imho a reason to get the first 2.0 firmwares! Maybe @Jason McNeil @tinawong @Diana@szkingsong.com and other reseller/manufacturer representatives could push the designers to resolve this issues? (Sorry to adress mainly kingsong representatives since i just know their names - and i have no idea how their firmware development state/implementations is in regard to tilt-back's) Attached you find the zip file with the original data in csv format for Current, Speed, Altidute, Pitch, Voltage and Altitude. The graph started at 26 Minutes and 26 Seconds, so the "interesting" data is starting at 26*60+26=1586.00 sec (first column). You have to divide the data for (Current,Speed,Altidute,Pitch,Voltage,Temperature) by (100,1000,100,100,100,10) to get the Values in (A,m/s,m,°,V,C). The 9Bot E+ sends Voltage values unfortunately at much lower sampling intervalls as the other values, so load dependend voltage drops are not really "visible". *1) while reaching/hitting the max torque speed limit one could feel the "softness" of the wheel, brake and balance it to come to a stable state again. But under the above assumption that one accelerated really hard to the limit, so the the generated momememtum takes one up until the cut-off speed that recovery is imho just theory. *2) If cut-off speed is reached before the max torque speed limit of the motor it would be really a very bad and irresponsible controller design! 9B_20160415_105325.zip
  9. As some practical input to the tiltback topic my graph from accelerating to fast and by this hitting the 20 km/h limit quite hard on my 9bot E+. Tiltback set in in two stages. The first at a pitch angle of about 7° and the second at about 10°. The second stage imho set in since i could not balance fast enough after the first stage begun - I could not put my weight "neutral" on the pedal, i stayed more on my toe tips and by this did not decelerate the wheel enough to stop the tiltback. After some endles seconds in the second stage i managed to put enough weight on the heels to brake the wheel enough to stop the tiltback: As seen in the graph the power demand is quite low compared to intense accelerating. The one current spike (almost 10A, ~600W) once the second stage set in could be the power needed to raise me standing on the toe tips from the ~7° to 10° pitch angle. I assume that the "rumours/stories/accidents" from faceplanting after tiltback kicked in are not primarily related to the tiltback it self but to too fast acceleration towards cut-off speed. Or also the (small) acceleration needed to tilt-back could be the last bit "needed" to reach the cut-off speed?
  10. Or a dc/dc converter is used to produce just this needed voltage for the constant current to prevent this power waste by voltage dropping over the mosfet.
  11. On your foto the bottom bank of mosfets has the same grey insulation film as this top bank?! The different parts of the heatshield are and should not be insulated - just some small amount of heat paste has a much lower thermal resistance! As already @esajstated the 6 low side mosfets have to be insulated from the heat shield - i assume you tried your wheel and it works fine? could it be that they use isolated washers and by good luck the screws did not touch the mosfets? one could decrease the thermal resitance for the high side mosfets by removing the grey insulation film and just using heat paste (if this are the mosfets which where not insulated and there is nothing else connected to the heatsink) - but before thinking about this i would triple check this. Also insulating all the mosfets should be the best solution - just in case one cable melts to it... if they did not use the heatshild as connection on purpose... so be very sure to put the plastic insulation ferrules on the same mosfets again and get new ones if they already show some wear. Non insulated low side mosfets will result in an immedeate bridge shoot through and smoking mosfets! so checking the insulation with an ohmmeter after reassembly could be a good idea too - or putting some halogen bulbs as current limiter into the supply line to test if everything works out...
  12. Be carefull while fastening the heatshield to the Mosfets again - you see the chip of metal at the third hole from the bottom? Plastic insulation pieces for the screws are used and still intact to prevent the screws from touching the heatshield? Also the nut on the other side?
  13. Could be a normal range - especially if you rode some hills and are a bit heavier than an average chinese... for riding steadily on a flat road (no inclines and no strong headwind) its not enough. 60 miles are absolutely out of reach... maybe going downwards with tailwind and home sickness. E+ and E batteries are swapable. Presumably also the c+ - but i don't know this. Imho also the P batteries can be used? with the e you definitely want a big battery - especially living in a hilly area! with my e+ (?320Wh) i made (with a nice hill at the end) just 10 km with one charge.
  14. Me too. So i hope this is just a "strange" photo - but beside the big paste blob it seems as if one could see a piece of paste below the mosfet... I like the concept of a powerfull 16 inch wheel with 100V batteries - i am looking forward to the reports around here! Especially how the two "main" points of ecodrift will be received: i understood he did not like the pedals and the casing (hurting ankles) and the "fading" power above 30 km/h... i assume there was also something with the case (how it is assembled?), but the translation was to weird to really get the point.
  15. Wow - the third photo seems to be the perfect example for how _not_ to mount a mosfet on a heatsink... a nice spacing between the mosfet and the metal and a huge blob of paste inbetween - or are my eyes deceiving me? https://forum.urban360.com/uploads/monthly_2017_01/IMG_0093.JPG.4eae24b91a5b8ad199633e838723659d.JPG According to @swvision's link in http://forum.electricunicycle.org/topic/6656-dyno-test-of-gt16/ to https://ecodrift.ru/wiki-article/laboratornyj-vzglyad-na-rockwheel-gt16/ the gt16 seems to be between the GW Monster and the GW ACM powerwise. The review is hard to understand (for me) with the google translate from russion to german - but i have the feeling the author has quite some points of critisism?