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WI_Hedgehog

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About WI_Hedgehog

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  • Location
    Milwaukee, Wisconsin, U.S.A.
  • EUC
    miniPro, KS-14SMD; EUC World Supporter

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  1. Do you mean the cost of a Smart BMS? I thought Gotway, and most other EUC manufacturers, don't monitor cells during discharge, only charge. If that's the case @Cody makes a good point. Aren't schottkey diodes $0.28 each out of China, less in bulk?
  2. From @Carbonos post: Monster V3 3108Wh compared to my friends on their Monster V3 84v 2400Wh. Mi riding weight is 100 kg. Last friday we went on a non stop 75km ride with lots of 40 kmh+ riding and my battery was down to 28%. From the EUC Comparison Table: Monster V3 84V: 2400Wh / 25Wh/mi = 96mi (154km) expected range Monster V3 100V: 1845Wh / 25Wh/mi = 74mi (119km) expected range (both match eWheels expected range) From @Carbonos post: 100kg = 220lbs = 15.75 stone 40kph = 25mph 75km = 47mi Expected range of his wheel: 3108Wh / 25Wh/mi = 124mi 3108Wh / 15.5Wh/km = 200km Calculated range of his wheel based on his ride statistics: 3108Wh * (100% - 28%) = 2238Wh => 90mi (145km) (so he seems to be coming up short on range) Carbonos expected battery capacity based on his ride: (47mi) (25Wh/mi) / (100% - 28%) = 1,631Wh Carbonos expected battery capacity if he's really pushing it: 75km = (47mi) (30Wh/mi) / (72%) = 1,958Wh 35Wh/mi = 2,284Wh (much lower than 3108Wh claimed) BUT, to double-check this for reasonability: If Carbonos battery capacity really is 3108Wh, he's using about double the normal power usage: (3108Wh) (72%) / (47mi) = 48Wh/mi (30Wh/km) If his friend's Monster V3 84v 2400Wh was at 5% (we don't know this number), his friend would have used: (2400Wh) (95%) / (47mi) = 48.5Wh/mi (30.4Wh/km) This is about the same as Carbonos, so the most likely outcome is: Carbonos battery is 3108Wh Carbonos rides like a madman Carbonos loves good food Not as likely (though also possible) is his friend's battery: is well-used and the capacity is not 2400Wh capacity never was 2400Wh was not fully charged was not discharged to 5%
  3. Is the package rated at 1/16 watt? (What is the wattage?)
  4. What is the value (in ohms) of the balance resistors?
  5. Income tax started out as a 1% tax on the richest 1% of the population. Drivers licenses started out as a slip of paper you sent off for in the mail. EUC insurance will be 3x the cost of car insurance due to the risk, and health insurance providers won't cover EUC riders, like with sky-diving. Regulations will be endless, like anything burrocrats get control of, and insurance mandatory. Stay under the radar so you can afford to enjoy wheeling.
  6. I'm sure I'll wait until next year as you're doing. Much the same though, was thinking KS-18XL, MSX, or Monster? Now it's how nice the V11 should be, and by Spring all the bugs should be worked out.
  7. To stop the beeps when it cannot find the wheel, touch the chat bubble in the upper right so it is hollow instead of solid. To exit the program and have it not run in the background, press the BACK button twice, then wait 4 seconds. The first press will display a notification to press the button again to shut down the program. The second press displays the "Good bye!" message and close the resources it is using and exit.
  8. InMotion keeps making me want this wheel more and more. Every time I read the forum there's something more positive that InMotion has done, such as the 2nd charger when they already have a reasonable purchase price. In fact, it's pretty hard to not buy the V11.
  9. The resistor will try to dissipate charge current when cell voltage is above 4.20V. (Note how many cells are in Parallel doesn't matter unless there is more than one BMS, as one resistor R is used per cell group, regardless of the number of cells in the group. This is the problem with basing charger current on what the cells in parallel can handle instead of what the BMS can handle.) P = I x E Power is greatest at the Constant Currant -> Constant Voltage crossover point. If we take the charger to be 84V 2A (note 3A was used be the thread starter, but I'm using a more conservative 2A, and not implying his charging habits are the cause of the fire): E (84V) / 20 cells = 4.2V average, varies by cell imbalance I (2A) / 20 = 0.1A P(resistor) = I (0.1A) x E (4.2V) = 0.42W (at normal clamping voltage) However, with two dead cells: E (84V) / 18 cells = 4.67V average, varies by cell imbalance I (2A) / 18 = 0.11A Granted, the balance resistor is going to try to clamp the voltage at 4.2V, but as other cells reach full charge the E across all cells tries to approach 84V: P(resistor) = I (0.11A) x E (4.35V) = 0.48W (attempting 4.20V clamping voltage) Not the end of the world: 1 - 0.42W/0.48W = 12.5% overload. Except the Chinese are usually trying to cut costs and don't build in a 1.5x safety factor. If we assume the higher Gotway Low Voltage Cutoff of 3.30V (average): 3.30V x 20 cells = 66V, 66V / 4.2V/cell = 15.7 (meaning 4.3 cells can die and the wheel will still run) So the worst case scenario is 4 cells die and the wheel still works after being charged. We can therefore calculate the very real possibility 3 cell groups die: E (84V) / 17 cells = 4.94V average, varies by cell imbalance I (2A) / 18 = 0.117A P(r) = I (0.117A) x E (4.7V) = 0.55W (attempting 4.20V clamping voltage) 1 - 0.42W/0.55W = 25% overload this can burn out the resistor, which then charges the cell to cutoff. Granted, we hope the BMS charge shutdown circuit kicks in before 4.7V, and it almost always will kick in far below that. We do have to remember all parts have an acceptable tolerance range, which in the US is typically 5%, so if we assume China uses 10%: 4.27V shutdown with 10% acceptable variance = 4.62V (pretty close to 4.7V, isn't it?) However, on average that's 4.48V, so we might be a bit over-estimating. Then again, @houseofjob has taken me to task for thinking this actually happens in China. Even if we tighten the assumption to 5%, that means some wheels will have 4.48V cutoffs, if the cutoff circuit is reliable. While the numbers can be argued, what we do know though, is we're starting to see circuit boards -and wheels- burning up. (and remember, a 2A charger was used in these calculations, not a 5A Fast Charger)
  10. You may wish to read this series of posts on balancing, which appears to relate to your situation.
  11. HOW EUC FIRES ARE GOING TO BECOME MORE COMMON SUMMARY: To minimize the risk, use the Charging Best Practices. A new BMS thread popped up that relates to what we've been talking about with balance charging. The BMS got cooked. This post builds on how cells get out of balance, and state what happens next. This problem is compounded by using any/all of: recycled cells, charging to 80%, and fast-charging. To quickly recap, one of the dangers in using recycled cells is some cells will be near their End Of Life and start to go out of balance quickly, which is unexpected on a wheel less than two years old. Battery voltage reported in an app and on the wheel is an average across all cells and will read as somewhere between 25% and 50% battery remaining, but the weak cell/cell group voltage will be below 3.00V, and the BMS in EUCs is not monitoring for this condition. As the rider continues on, the strong cell/cell group voltages will continue dropping (say 3.5V), but the weak cell voltage will go below Critical Low Voltage (say 2.5V). This causes a permanent chemical change in the weak cell/cell group where the cell shorts, as if removing it from the circuit. The full charger voltage is applied to the remaining cells, as stated previously. Here's what happens next: Weak/used/older/recycled/aging and "cells in the middle of the pack that can't cool as fast as the outer cells" have less capacity than strong cells, therefore, they reach full capacity (4.20V) sooner. The charger applies power across the whole pack, so the weaker cells which are fully charged must somehow stop themselves from being charged; because they don't have this ability, the Battery Management System does this by employing a balance circuit for that cell/cell group. The balance circuit turns on and bleeds off current from the charger for that cell group. Normally this works well. Consider the following: Fast charging increases the current through the battery pack, and therefore through the cells. The balance circuit resistor must bleed off this extra current. When there are dead cells, the full charger voltage is applied to the remaining cells. This higher voltage is applied to the balance circuit resistor, which must now bleed off the extra current caused by the extra voltage. In both cases, the resistor must dissipate more power than it was designed to handle, and it's a very tiny resistor as seen in BMS pictures. The resister overloads, and the balance circuit can't dissipate the extra power. In the worst case scenario the resister burns out. Either way, the balance circuit can't dissipate the extra power and the cell group continues charging to the point of being over-charged, damaging the cell group. (This can quickly cause those spiky dendrites to form.) Hopefully the BMS stops the charge, preventing a fire. However, this leaves cells in an unbalanced state, worsening the battery condition (a circular problem). Because there is no alert, the user sees a shorter charge and shorter riding time. There is also more stress on what's left of the battery, especially on the under-charged cells. With the added stress, when cells go under-voltage they heat up quickly, potentially starting a fire. (There is a safety mechanism, hopefully it works. If not...) To minimize the risk, use the Charging Best Practices. Once the rider sees shortened charge and riding times, cells should be capacity tested and matched. Given the time & cost in the teardown, testing, and rebuild process, coupled with the expected lifespan of the used cells in an EUC application, it's quite possibly best to start with new cells and rebuild a pack with a new, unstressed, reliable BMS, depending on the condition and number of the surviving cells, plus taking new, longer-lasting cell technology into consideration.
  12. I think it's possibly more like top-tier sellers forcing battery exchanges, and I should have stated that more clearly. Gotway is probably not going to do more than they absolutely have to. If that is the case, it's potentially very short-sighted, and could cause a similar ban to the cheap-China-hoverboard ban where poor lithium battery management caused a fire in a plane's cargo hold leading to a complete ban on low-quality imports for a while. (I know someone who lost $150,000 because the ship was prohibited from unloading the hoverboard cargo. Of course, the Chinese were already paid, so what did they care? They didn't. And that ended a lot of sales in the short term, and led airlines to ban lithium batteries. Again, the Chinese didn't care. So in this case, it's possible we'll see more Gotway/used TESLA cell fires in the future. IF that's the case, I hope it's only a Gotway ban vs. a wheel ban.)
  13. Well, there's the other shoe. I'm going to guess the reputable sellers got the Panasonic 21700 information from Gotway. Gotway possibly bought refurbished cells, and is now recalling them because, quite frankly, using used cells not designed for this task is generally a bad idea. China does a lot of "recycling," that's how all those plastic straws ended up in the ocean. Now we have the evidence they imported TESLA batteries in bulk and are ripping them apart for the cells. I can understand third party sellers using them, figuring "they seem good and are cheap, they'll last six months." And as @houseofjob said, anything for a buck. If Gotway marketed the wheels as having TESLA cells, and they are actual TESLA cells, they're used cells, selling at more than 18650 prices. If that really is the case, I'd cancel my Veteran order knowing that will most likely be more of the same in a different wrapper. I read the top EUC racers build their own battery packs because factory "isn't great." Maybe this will be proof. Gotway quality was not good in other areas, I can understand it could be horrible here too. Lot of speculation, but enough proof for me to wait to see how InMotion's suspension fairs. Thanks guys, this really shed light on the rumors.
  14. So I learned something new, thank you @houseofjob !! Those sellers do indeed say Panasonic 21700 to this day! As far as I could find, Panasonic makes only one 21700 packaged cell, exclusively for TESLA. @Mike Sacristan seems to have gotten to the bottom of where the used cells are coming from. While there aren't any laser markings (my mistake), there are the three unique squiggles on the bottom of the cell as Mike mentions, though there is also the ultrasonic weld joint from the fuseable wire on the top: The seller adds various colored wrappers.
  15. I think you read my post incorrectly, as my position is since TESLA automotive cells are not available to anyone but TESLA, they are only used in-house, and TESLA doesn't have enough cells for their own use, the cells in Gotway wheels most likely aren't new TESLA cells. If TESLA/Panasonic was selling TESLA cells to third-parties, it would be big news. If for no other reason than real TESLA cells are very traceable, Gotway probably wouldn't buy stolen ("siphoned") cells to put in new EUCs. If Gotway was using TESLA cells, there should be evidence of it by now. Without any evidence at all, it is not proper to imply Gotway is being disreputable in that manner. I stated knockoff ("fake") cells are a reality, as are many other items. While a third-party could put knockoff or recycled cells in, so far nobody has reported finding cells marked "TESLA" in their Gotway (that I'm aware of). Real TESLA cells are not available anywhere but inside TESLA batteries. As I stated previously, "other cell manufacturers saw it as a good idea and copied the cell dimensions (the chemistry is specific to Tesla and otherwise unavailable)." Real TESLA cells do have the highest energy density, but are not as well suited to applications outside TESLA vehicles--other chemistries do better. Am I wrong? Has someone found cells marked "TESLA" in their Gotway??? I've only read that one seller was claiming Gotway's 21700 cells were sourced from salvaged TESLA batteries, which is why they were selling Gotways with 18650 cells. Members suspected the claim stemmed from them having a stock of Gotways with 18650 cells that they needed to sell. One seller in China making an unsupported claim. No wheels reported to have cells marked TESLA.
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