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esaj last won the day on May 11

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About esaj

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  1. I don't actually check the voltages themselves, but over the last winters, I've stored the wheels discharged to something like 30-40% for 6-7 months at a time, and they've never discharged enough to even drop much, ie. looking at the LEDs showing the charge, I've had 3-4 LEDs on out of 9 on both KS16's when putting them to storage and still had 3 LEDs on in the spring. All batteries were left connected to the wheels, since KS's don't draw power from them when off (most wheels don't, with the exception of Ninebot Z-series which have relatively huge vampire drain that sucks full batteries to empty in about a month or so, those things need to be charged often during storage, or preferably, disconnected from the wheel mainboard!). For other than Ninebot Z's, likely the only thing using power when the wheel is off is the BMS, and the current it draws seems to be somewhere in the microampere-range, and then it won't matter if the packs are connected to the wheel or not. Four 16S1P -packs each with their own BMSs I've stored in a ground basement under the house, that has temperatures ranging from freezing to maybe 15-20C, have been there for about 2-3 years without charging in-between, when I checked this spring, they were around 56V (I think I charged them to around 57-57.5V when I put them there).
  2. The ACS712 is a current sensor microchip using the hall-effect (magnetic field caused by flowing current) to measure the amount of current and output it as an analog voltage signal. https://www.allegromicro.com/~/media/Files/Datasheets/ACS712-Datasheet.ashx My best guess would be that the controller might go into some sort of overvoltage lockout if the motor isn't turning and it senses too high voltage (48V controller sounds like it's meant for something like 11S or 13S batteries). Have you tried discharging the batteries to a lower voltage to see if it then starts running? Then again, if it starts running without load (if you mean you turned the bike upside down by "backwards"), it might be related to the ACS712 (controller detects overcurrent when the motor's still stalled at start-up), in which case maybe a small voltage divider to drop the detected current value might work? EDIT: No, it won't work, the sensor's bidirectional, so it would move the offset away from the "zero current" -point at half the supply voltage, it would need a more complex set up with an op-amp or such... But I'm really just guessing... Either way, perhaps it would be best to get a controller that has suitable maximum voltage for the batteries? A better place to ask might be something like the Endless Sphere (e-bike) forums: https://endless-sphere.com/forums/
  3. Yeah, time has flown pretty fast looking back. I removed the foam after the first summer, no video though Not that there'd be much to see, I purposefully used a crappy 2-sided tape (not the 3M-stuff) that was easy to peel off and left without leaving marks. If it would have left residue, I'd have just cleaned it off with IPA anyway... But here it is in its original beauty: <3
  4. Yeah, the funny thing is that the price has stayed pretty much the same since the release. Guess there's enough demand for them still that there's no need to drop the price. I've been happy with mine, zero issues after 3 summers and while I haven't measured the actual battery capacity since the first summer, I haven't noticed a drop in the capacity so far (although likely after that long there is some).
  5. I guess they're pretty random. But you could try mailing them directly and ask. The owner seems like a nice guy.
  6. Yeah, the sale price is only for the 420Wh version. Check out other possible options here:
  7. 1RadWerkstatt: https://www.1radwerkstatt.de/epages/80603321.sf/en_GB/?ObjectPath=/Shops/80603321/Products/KS16[1] Currently 1029€ for the 420Wh version, 1449€ for 840Wh. Free shipping within EU-area. Bought my KS16S (White, 840Wh) from there in the spring of 2017.
  8. Pari kertaa varmaan sen ajolasi-tyypin nähnyt, yliopiston liepeillä ja uudelleen Tourulan suuntaan menossa, musta pyörä leveällä renkaalla, näytti Ninebot Z:lta. Omat ajelut loppui tältä vuodelta tällä viikolla kun tiet oli jäässä aamuisin jo heti alkuviikosta, ja näyttäisi että lämpö pysyttelee nollan alapuolella tästä eteenpäin.
  9. @EUC Extreme käytti ruuvattavia nastoja, ilmeisesti pito on erittäinkin riittävä "normaalissa" ajossa, tosin nastat taisi olla verrattain kalliita (luokkaa ~100€ / rengas?). EDIT: Muistelisin että ulkokumeissa on käytetty jotain vahvikkeita (kevlaria?) sisäpuolelle liimattuna ettei nastat puhkaise sisäkumia, joten jonkun verran värkkäämistä noissa on.
  10. RECOM also does board-mountable switching-modules with isolation and whatnot, but the issue is the price. If the end user should be able to build / buy the parts for about 25-30€ total or less, the module alone would pretty much eat the entire budget
  11. I just bought a < 10€ guitar stand from Thomann years ago. Old picture, beautifully covered KS16S in the front
  12. I'm fairly certain that the above is wrong, but if I'm wrong, somebody please do correct me, always happy to learn. In King Songs, the BMS does not "output" voltage towards the charger, there's a reverse polarity protection in the charging side which as a side-effect also prevents reading the battery voltage from the charge port with a multimeter (you might see a few volts as the mosfets leak a tiny bit of current "backwards", but not the actual voltage). On the other hand at least some older Gotways, if not also all the new ones, don't have reverse polarity protection, and you can read the voltage from the charge port. However, the charger does not "use" this voltage reading whether it's there or not, instead, the charger drops its own output voltage if the current limit (like 5A) is hit until the current stays at that limit. It cannot "directly" control the output current, but the control is done through altering the output voltage. This is the CC (Constant Current) -charging phase. Once current stays within this limit when hitting the maximum output voltage, the CV (Constant Voltage) -phase begins, where it just keeps the output voltage at the maximum (like 84V), and the current dies out slowly as the battery charges and the battery voltage goes up towards the charger voltage (the difference between the charger output voltage and battery voltage drops, since the resistance between the two is more or less constant, the current drops: I = U/R). I'd speculate (like others have before) that in this case the faulty charger output voltage has raised high enough to destroy the BMS charging-side protection mosfets. Never seen the KS BMS, but I'd guess they're using something like 100V max mosfets there, and a high enough voltage spike from the charger has fried the protection, allowing the cells to overcharge. They might have gotten severe damage at this point, but not enough to cause a fire. Once the badly damaged cells were charged using the normal charger, an internal short circuit inside a cell or such caused the temperature to raise beyond the critical "thermal runaway" -point (something like 125...150 Celsius), at which point the cell catches fire that keeps feeding itself. But that's all just guesswork.
  13. Rigol makes some relatively cheap oscilloscopes (300-400€ for 2/4 -channel 50MHz bandwidth, hardware unlockable to 100MHz + double memory etc): https://www.batronix.com/shop/oscilloscopes/DSO.html Right now they have a deal where you get all the options at the same price, except the bandwidth? I have the DS1054Z, haven't unlocked all the options (basically they should be bought separately, but there's a key generator online... ), but it's already out of warranty (3 years), so maybe one day if I need more bandwidth or such. To my knowledge, all the 4-channel DS1000's (1054, 1074, 1104) are actually the same hardware, except for the logic analyzer in the Plus-models, otherwise the difference is just the (software limited, unlockable) options. They're not super high quality precision instruments (such cost high 4-figures or 5-figures anyway ), but easily good enough for occasional hobbyist usage and they've got a lot of features for the price. The only downsides I've hit is that the internal voltage noise is relatively high if wanting to measure really low ripples (can't seem to measure reliably below about 0.8mV, which seems to be a lot for an oscilloscope) and the FFT is slow and not very precise, so a separate spectrum analyzer would be needed for such measurements.
  14. Where is the data captured from if you don't have a Charge Doctor, from the wheel telemetry? That's a lot of noise... I've never looked very closely at the wheel voltage measurements, I'd guess that at least in most cases it's just a voltage divider feeding directly into an ADC-pin of the MCU, and if done "poorly" (no filtering, lots of SMPS noise in the system), there can be a lot of noise in the signal. They (likely) just divide the voltage, so the battery voltage range is "mapped" from 0-67.2V to 0...less than 3.3V (to leave headroom in case of overvoltage, so it won't blow the ADC), say 0...3.0V. 12bit ADC can give 4096 different values, but if roughly 10% of the top end is left for handling possible overvoltage and spikes, that leaves around 3600 values for the entire range. 67.2V / 3600 = about 19mV per LSB, which isn't that bad really, should be easily enough resolution for battery voltage measurement. The noise amplitude seems to go up to around +-0.5V from the average, so a total of about 1000mV or about +-50 on the ADC-reading, so likely it's not just "normal" noise of a few LSBs that tends to end up in the measurements unless special care is taken in layout, shutting down peripherals etc. Maybe there's no filtering at the divider at all? If you have an oscilloscope and some courage, you could try to measure the ADC-pin noise when it's not charging and during charging. One possible source might be the charger itself, I don't think that the cheap chargers have much in terms of filtering the output noise, so that might be another place to take a peek at (with an oscilloscope).
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