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esaj last won the day on March 31

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  1. Since nobody seems to have made any offers (although they might have via private messages), I'll get the ball rolling by offering 500€ + shipping. But, I doubt that 1) Bjorn is willing to sell at that low price and 2) even if he was, nobody else wouldn't go higher than my offer
  2. The BMSs usually have special protection ICs that oversee the battery status, but mostly that's exactly what causes the wheel to just shutdown in case voltages drop too much. For example, Cranium tore down his Ninebot back in the day, and found out that the BMS uses SH367004-lithium battery protection/balancing chips, unfortunately the datasheet's in Chinese, here's a google translate of the overview: Switch between 3/4/5 tandem applications via the SEL0 / SEL1 pin High-precision voltage detection function: (for single-cell batteries) -Overcharge protection threshold voltage: 3.3V - 4.5V (50mV a file) Threshold voltage accuracy: ± 25mV -Overcharge protection release voltage 1 : 3.2V - 4.5V Threshold voltage accuracy: ± 50mV -Over discharge protection threshold voltage: 1.8V - 3.0V (100mV a file) Threshold voltage accuracy: ± 50mV -Over discharge protection release voltage 2 : 1.8V - 3.4V Threshold voltage accuracy: ± 100Mv Two-stage discharge overcurrent detection function: - discharge overcurrent 1 protection threshold voltage: 0.05V - 0.3V (50mV a file) Threshold voltage accuracy: ± 15mV - discharge overcurrent 2 protection threshold voltage: 0.2V - 1.0V (100mV a file) Threshold voltage accuracy: ± 100mV Two-stage charge overcurrent detection function: - Charge overcurrent 1 Protection threshold voltage: 0.05V - 0.3V (50mV first gear) Threshold voltage accuracy: ± 15mV - charge overcurrent 2 protection threshold voltage: 0.1V - 0.5V (100mV a file) Threshold voltage accuracy: ± 40mV Charge and discharge temperature protection function: - Charging Low Temperature Protection Threshold Temperature: -20 ° C, -10 ° C, 0 ° C Threshold temperature accuracy: ± 2 ° C (typical) - Charge and discharge High temperature protection threshold temperature: 50 ° C, 60 ° C, 70 ° C Threshold temperature accuracy: ± 2 ° C (typical) Balance function 3 : - balanced open threshold voltage: 3.1V - 4.4V (50mV a file) Threshold voltage accuracy: ± 25mV Wire break detection function External capacitor can be set to overcharge protection delay, over discharge protection delay, discharge Overcurrent 1 protection delay and charge overcurrent 1 protection delay Charge / discharge overcurrent 2 protection delay and temperature protection delay Internal fixation CTLC / CTLD pin gives priority to CHG / DSG pin output Wide operating voltage range: 3V - 26V Wide operating temperature range: -40 ° C to 85 ° C Can be used in cascade Low power consumption: - Normal operating current consumption: 25µA (typical) - Low power consumption current consumption: 4uA (typical) Package: 24-pin TSSOP Overdischarge status When the arbitrary section of the cell voltage is less than the overdischarge detection voltage (V DV ), and this state duration exceeds the overdischarge detection delay (t DD ), the SH367004 series The DSG pin outputs a GND level to turn off the discharge MOS tube. The above state is referred to as an overdischarge state. When the SH367004 is used as the master chip, the overdischarge status is released (the system does not enter the low power state) when any of the following conditions are met: (1) The CHSE pin voltage of the SH367004 is higher than GND (not connected to the charger), and the voltage of the overdischarge protection is higher than the overdischarge Pressure (V DRV ) (2) The CHSE pin voltage of the SH367004 is less than GND and the CHG pin is output high (charging the charger and charging current), and all batteries The voltage is higher than the overdischarge detection voltage (V DV ); When the SH367004 is used as an auxiliary chip, the overdischarge status is released (the system does not enter a low power state) when any of the following conditions are met: (1) Trigger over discharge protection The cell voltage is greater than the overdischarge recovery voltage (V DRV ) (2) When the BALI pin of the SH367004 is input low (charging the charger and charging current), and all the cell voltage is higher than the overdischarge detection voltage (V DV ) So apparently no bypassing, the overdischarge protection will just shutdown the battery pack output via the discharge mosfets ("The DSG pin outputs a GND level to turn off the discharge MOS tube") if the cell voltage(s) drop too low. Don't know if there are ICs available with the possibility of bypassing a faulting cell, probably? That would at least keep things powered and assuming the firmware could detect the cell failure, it could then at least warn you with some beeping or whatever, and with enough power, tilt-back to tell you to stop... EDIT: Actually, the original Firewheel packs had an extra wire coming to the mainboard, when it was disconnected, the mainboard would start to play a message saying something about "bad cell in battery" when turned on... don't know what would have happened if there really was a bad cell and it would detect it during riding, I only tested it with the mainboard out of the shell, but at least it apparently could detect cell failure. Maybe I could some day open up the heatsink of the BMS and check what chip(s) it used for monitoring.
  3. But... that's a 5-pin connector? Vcc, GND + 3 hall -wires, I guess? There's a gazillion different connectors out there, if you're worried about it coming off, you could try replacing both ends with something that has plastic pins to lock in place: The hall-signals should be very low amperage (a few tens of milliamps at most, I'd expect?), so "almost anything" should work, AFAIK.
  4. No, the 2900mAh cell or pack won't drop to 0amps, the voltage over the paralleled batteries should stay the same at all times. Due to the internal resistances, the actual currents flowing through each pack probably differs somewhat, though, so the one or the other pack is probably giving a larger "share" of the 2amps than the other, but that's nitpicking. That's how parallel circuits work, refer to for example. It says pretty much in the beginning the very basic law of paralleled circuits (or components, or battery packs...): "The first principle to understand about parallel circuits is that the voltage is equal across all components in the circuit. This is because there are only two sets of electrically common points in a parallel circuit, and voltage measured between sets of common points must always be the same at any given time." -> The same polarity poles of the batteries are connected together (negative -> negative, positive -> positive), so the batteries are in parallel. There cannot exist two different voltages between the same two points at the same time. As a bad analogy, kinda like you can't have two different distances between two objects at the same time, or something... The voltages of both batteries are still the same. Slightly different portion of the total current might flow through one or the other pack, but again, they will reach the fully charged voltage at the same time.
  5. AFAIK, neither cell will get overcharged, but there will be lots of current flowing (the actual amount depending on the resistance of the wiring and the internal resistances of the cells, which are both very small, plus the voltage difference). The wires might melt and the cells could get damaged, and/or overheat, possibly ending up catching fire or exploding. That's why the voltages should be as close to each other as possible before paralleling (single) cells or batteries. When paralleling packs, probably the easiest way is to charge both packs to full (as they should then be at or very near the same voltage). Another trick is to use a (power) resistor of "suitable value" in between, so the current will stay low until the voltage reaches equilibrium. As for paralleling packs with different capacities/cells, I think hobby16 once mentioned it should be ok (of course taking care that the voltages are the same when they're first connected). Don't know if it can cause issues further down the line, like maybe the "weaker" pack might age slightly faster.
  6. I've written a bunch of info on the batteries (but not that much about the charge ports) here: If you open the casing, you should find two wires running from the charge port to the battery through some connector. Check that the wires and the connector are firmly connected. If you poke around the battery, it's not super dangerous, but take care of not short-circuiting it etc, as mentioned in the above post. If you have a multimeter, you can try measuring the voltage of the battery to see if there's any charge in it (I think the older Rockwheels used 16S-packs also, so the voltage should be somewhere between 48V for very much empty pack, up to around 67.2V for full pack), but if you feel uncertain about it, maybe better leave it alone. The cells "age" faster when kept at high voltage, storing in full charge is pretty much the worst option, especially if the storing temperature is high (above room temperature). Mostly this seems to show up as permanently declined maximum charge, how much of the capacity was lost depends on the time in storage, temperature and the cell voltage. More or less "ideal" storing environment would be cool (but not freezing) and the cells should be kept at about 30% charge (around 3.6-3.8V per cell, for a 16S pack that's about 57.6-60.8V), and only charged if necessary (ie. they start to drop towards 3V or so). If the voltage drops too low (2.5V per cell or below, around 40V for 16S-pack) for a longer while, the cells can start forming metallic "dendrites" inside themselves, and should not be used anymore, as they can cause internal short circuits. As usual, take all of the above with a pinch of salt, I'm not a battery expert, this is just based on what I've read (and measurements from some more or less worn 18650-cells I have laying around, as well as higher quality 16S-packs I have in storage).
  7. The mosfets contain body-diodes that will allow reverse current flow with some voltage drop, so if the sine-wave from the phase gets the source voltage high enough vs. the drain (high-side, from motor phase to battery +), the diode will conduct: Same for the low-side, but as the source there is connected to common ground, it only conducts when the phase on the drain-side goes far enough below the common ground voltage. Consider the following simplified example: The motor produces a sine-wave, in this example I used 1KHz wave with 0V offset and 30V amplitude (so +-30V at peaks), marked as "Motor_Phase". The other side of the signal source actually goes to ground through another phase, but it isn't shown here, otherwise there wouldn't be a closed loop for the current to flow. The high side mosfet (U1) has it's drain connected to the main voltage line (from the battery/mainboard), marked as "To_Mainboard". Of course the gates of the mosfets aren't really floating, but in this simulation it makes no difference. I've added a small capacitor and a resistor to the line to show the effect... basically when the voltage from the "Motor_Phase" - body diode voltage drop goes above the voltage of "To_Mainboard", the diode will start to conduct. Voltages from the Motor_Phase and To_Mainboard over 10ms simulation period: There's small ripple on the V(to_mainboard), as the capacitor is being discharged through the resistor to ground when the diode is not conducting, with a larger capacitor and/or resistor, it would be more steady, with lower values you'd see more fluctuation, as the capacitor would discharge more faster. Current through the high-side mosfet source to drain (so in reverse) vs. the voltages: The green is the motor phase, red is the "to_mainboard" -voltage, as you can see, there's current flowing through the mosfet in reverse each time the phase-voltage goes above the "to_mainboard"-voltage + diode-drop. There's a large spike at start, because the capacitor isn't charged yet and the voltage of the "to_mainboard" starts at 0V. In real-life, the currents wouldn't be this large, as I haven't entered any ESR -values for the cap, and the phase voltage would actually drop fast once the magnetic field starts to collapse... But this is just to show the basic idea, not to simulate it totally faithfully vs. the real world
  8. You didn't store it fully charged by any chance? Still, even if the cells are degraded, I'd expect it to take in at least SOME charge, sounds like it isn't charging at all. Try checking the wiring from the charge port to the battery pack
  9. Can't say for sure, it would help to compare it with more datasheets from different cells/manufacturers, maybe that kind of "torture test" is some sort of (de facto) standard in the field... at least they aren't giving a too optimistic view of the lifetime?
  10. Things that probably affect the poor cycle count are that they've used high charging current (6A, almost 2C for 3200mAh cells), pretty much the maximum possible 4.2V -> 2.5V cycles, and discharged with continuous high currents (10-30A). Still, it's not exactly stellar when it comes to the cycle lifetime Of course in real use, you don't use that high currents all the time, and the wheels usually force you stop around 3.0V / cell? Compare that to what Battery University says about the usual cycle lifes for the lithium-batteries ( ), although they seem to define 100% depth of discharge as 4.2 -> 3.0V : Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1,500mAh pouch cells for mobile phones were first charged at a current of 1,500mA (1C) to 4.20V/cell and then allowed to saturate to 0.05C (75mA) as part of the full charge saturation. The batteries were then discharged at 1,500mA to 3.0V/cell, and the cycle was repeated. The expected capacity loss of Li-ion batteries was uniform over the delivered 250 cycles and the batteries performed as expected. Figure 1: Capacity drop as part of cycling. Eleven new Li-ion were tested on a Cadex C7400 battery analyzer. All packs started at a capacity of 88–94% and decreased to 73–84% after 250 full discharge cycles. The 1500mAh pouch packs are used in mobile phones. Courtesy of Cadex Depth of discharge Discharge cycles (NMC / LiPO4) Table 2: Cycle life as a function of depth of discharge. A partial discharge reduces stress and prolongs battery life, so does a partial charge. Elevated temperature and high currents also affect cycle life. Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity. 100% DoD ~300 / 600 80% DoD ~400 / 900 60% DoD ~600 / 1,500 40% DoD ~1,500 / 3,000 20% DoD ~1,500 / 9,000 10% DoD ~10,000 / 15,000 Charge level (V/cell) Discharge cycles Available stored energy Table 4: Discharge cycles and capacity as a function of charge voltage limit. Every 0.10V drop below 4.20V/cell doubles the cycle but holds less capacity. Raising the voltage above 4.20V/cell would shorten the life. Guideline: Every 70mV drop in charge voltage lowers the usable capacity by about 10%. Note: Partial charging negates the benefit of Li-ion in terms of high specific energy. [4.30] [150–250] [110–115%] 4.25 200–350 105–110% 4.20 300–500 100% 4.15 400–700 90–95% 4.10 600–1,000 85–90% 4.05 850–1,500 80–85% 4.00 1,200–2,000 70–75% 3.90 2,400–4,000 60–65% 3.80 See note 35–40% 3.70 See note 30% and less
  11. Mods can see the email addresses the users are registered with, but I wouldn't contact anyone just to check up on them, it would seem pretty weird The Fat Unicyclist has last been seen on April 6th, I think he mentioned having to travel a lot with work, so maybe he's just on one of those trips. HEC has last visited about a month ago... Cloud is a moderator himself, last visited April 11th. Can normal users see the "Last visited" -dates / times of other users?
  12. I think Rockwheel GT16 & Gotway MSuperV3, ACM and maybe Monster use IRFP4110 or IRFB4110. Might be used in other higher voltage wheels also?. The difference between the P- and B-models is that the P-model uses a more heavy-duty TO-247 -package, while the B-model has the TO-220, other than that they should be pretty much the same.
  13. I certainly can't say for sure, but the winding would still suggest PMSM? For the noise, I don't know, it seems the more powerful motors are noisier, but even PMSM probably isn't totally silent, just less noisy than a BLDC? Also, another source says that the space-vector commutation used in FOC has higher torque ripple, which might cause more noise too: "Space-vector commutation is even more computationally intensive. And while it has more torque ripple than a sinusoidal drive, it makes higher utilization of the bus voltage and is therefore more efficient in terms of power." (The first answer also has nice images of the waveforms and comments) It's still a 3-phase motor, but the phases are always connected either on the high or low-side, they're not left floating like with the BLDC trapezoidal control. At least I'm fairly sure on that Trapezoidal: Only two phases are connected at a time, the third one is floating (not connected to high- or low-side of its half-bridge). FOC / Space-vector commutation: All the phases are connected to either high or low side at all times (except during transitions, actually). Both of the above images show just the whether they're connected to high- or low-side (or neither, in case of one phase for trapezoidal control), but of course PWM is also involved to control the voltage, the images just leave that out. As the motor turns, the phases are ramped up and down at varying duty cycles. I get the rotational matrices (I'm a game programmer, remember? ), but where and how to get the reference frame angles and such is still a bit of a mystery to me (have to re-read some papers and more sources obviously)... Probably I should get some simple motor controller and a small PMSM to try it out in practice to gain better understanding. I can't say I really understand it all, but I keep trying to learn
  14. I tried to count the slots from this picture, but it's pretty hard I think there are more than 54 slots? Rehab can probably count them from the real thing and enter the values in the calculator... But also the amount of turns and the wire gauge would have to be known to not alter the characteristics of the motor? The mainboard firmware is likely "tuned" to the original motor characteristics...