Jason McNeil Posted August 30, 2015 Share Posted August 30, 2015 Hobby brought up this issue for the GWs, but it seems to also apply for the King Song Wheels as well. I was told by King Song that the low voltage notification is 54v & the get-off-now threshold is 48v. So ran the KS800W on a full battery, just below the maximum cruising speed of 27kph, for almost exactly 1.5hrs.Performance definitely ebbs away at around 56v, but contrary to what I've been told by KS, at 54v the pedal-tilt angle becomes unrideable & you're forced to dismount. If the Wheel is powered back on, it simply doesn't respond, e.g. the lights turn on, but the motor does not engage. At this cut-off threshold the usable capacity of battery-pack is only about 500Wh, which is why adjusting this threshold is so important, otherwise 25% is simply wasted... Link to comment Share on other sites More sharing options...
KaleOsaurusRex Posted August 30, 2015 Share Posted August 30, 2015 at 54v the pedal-tilt angle becomes unrideable & you're forced to dismount. If the Wheel is powered back on, it simply doesn't respond, e.g. the lights turn on, but the motor does not engage. At this cut-off threshold the usable capacity of battery-pack is only about 500Wh, which is why adjusting this threshold is so important, otherwise 25% is simply wasted... I feel like this is why King Song is the best brand right now. Conservative battery behavior, and a locking low battery limit after which the unit will be unridable needs to be the standard for this technology until other methods are developed to keep the rider safe. The only other brands I know that do something similar are Ninebot and Firewheel, both of which have their own set of disadvantages as well. Does anyone know any other brands that feature a locking low battery cut-off like this?@Jason McNeilCan the cut-off threshold be adjusted by the app, or is it something that King Song would need to change? Would it even be wise to have a more liberal cut-off, or is this conservative cut-off an important safety feature of the unit? From my readings, it seems to me that in order to avoid various types of unexpected shut down, this conservative behavior is exactly what I've been looking for all this time, and this post makes me so happy to be offering King Song as my flagship brand.Jason, I really want to thank you for doing these tests, and for your opinions about the results as well, as I lack the technical knowledge to do it myself. Link to comment Share on other sites More sharing options...
robca Posted August 30, 2015 Share Posted August 30, 2015 I want to particularly commend @Jason McNeil, who as a distributor might be tempted to hide (or, at least, not publicize) information like this that could drive customers away from the brand (even if, as @KaleOsaurusRex points out, this cuts both way). We need more people/companies/distributors who, like Jason, put the customer first, and share all available info, good, bad and neutral, to help customers make the right decision. Kudos Link to comment Share on other sites More sharing options...
Kevin Posted August 30, 2015 Share Posted August 30, 2015 Performance definitely ebbs away at around 56v, but contrary to what I've been told by KS, at 54v the pedal-tilt angle becomes unrideable & you're forced to dismount. If the Wheel is powered back on, it simply doesn't respond, e.g. the lights turn on, but the motor does not engage. At this cut-off threshold the usable capacity of battery-pack is only about 500Wh, which is why adjusting this threshold is so important, otherwise 25% is simply wasted... I'm actually with Kale on this one.54V corresponds to a per-cell voltage of 3.375V, which is very low. Take a look at this chart of voltage vs. discharge:http://www.electronicsnews.com.au/getmedia/8ad59ccf-ada7-4c1e-b1d5-0c3e6caac755/PMFeat_Figure_1.aspxLi-Ion voltage decline is not linear, and 3.375V falls within the tail end of the curve, where the voltage rapidly degrades with further usage to the 2.5-2.8V range where the BMS cuts it off for safety reasons (the commonly used expression seems to be "may vent with flame"). In my personal experience, adjusting the cutoff from 3.375 to 3.2 or 3.1 may get you an extra few %, and below that will get you basically nothing - a few seconds worth of time if anything. It's entirely possible that originally they had the cutoff at 48V (3.0V per cell), and found this simply didn't reliably give enough time to safely force a dismount before completely running out of steam. If this was the case, I can certainly understand bumping the thresholds up at the last minute without notifying the marketing folks.However, if the actual capacity is only 500Wh that's a separate issue... how did you arrive at that figure? Link to comment Share on other sites More sharing options...
esaj Posted August 30, 2015 Share Posted August 30, 2015 I want to particularly commend @Jason McNeil, who as a distributor might be tempted to hide (or, at least, not publicize) information like this that could drive customers away from the brand (even if, as @KaleOsaurusRex points out, this cuts both way). We need more people/companies/distributors who, like Jason, put the customer first, and share all available info, good, bad and neutral, to help customers make the right decision. KudosJason McNeil and KaleOsaurusRex are one of the few "honest salesmen" I've ever met (or at least seem to be, if such things even exist ). They have the passion for the products they sell, and don't hide the downsides, unlike most big chains and people looking to just make a quick buck, who just pick up the "next big thing" to their catalogs (usually some cheap generic or Airwheels) and start selling them, without actually even understanding what it is that they sell... Try to buy some generic from a big chain and go ask some more specific questions about it... I'd bet the answers for everything that's not directly in the manufacturer spec sheet is "We don't know". "It says here it has something called 132Wh battery and you can ride 30km on it". "What's a BMS?". "I'm sure it works just fine, if it doesn't, bring it back and we'll send it to warranty repair overseas". And don't even think they have any spare parts, repair service or such. The one and only advantage which they have is the price (if they order in very large bulks or simply can keep their margins really low due to large volume of all sales), which in a way is shame, as more "small-time" dealers usually can't compete with that, and of course people (myself included) want to buy it cheaper... Not that I'd buy a generic anymore, but if they were selling more quality brands with either with substantially cheaper price, or especially if they'd have it available right-off-the-shelf locally, I must admit I'd probably get one from the big chain Except, now that I know (well, "know" and know) people like Jason and Will, I might be ready to put more money on it, just to support all the work they've done so far. Over those two, in my case Jason has the advantage of being in the EU-zone (so no local customs charges & VAT for me, I think?). I think I know where I'd order a Kingsong, if I ever decide to get one... Right now I'm (probably) in a more dire need of a new Firewheel mainboard, though Link to comment Share on other sites More sharing options...
Donafello Posted August 30, 2015 Share Posted August 30, 2015 I actually know someone who mentioned his 14in 800w motor shuts down when it gets to hot. And has to be shut down for a few minutes before he can ride it again. I'll tell you this though I love the look of there 18 model and will be picking one up from will as soon as they are released. I can't wait to see the reviews of the current people waiting for there 800w;) Link to comment Share on other sites More sharing options...
KaleOsaurusRex Posted August 30, 2015 Share Posted August 30, 2015 @DonafelloMind providing a link? I always like to track down this kind of behavior to the best of my ability in order to learn more about these machines. It was a King Song? Link to comment Share on other sites More sharing options...
Cloud Posted August 31, 2015 Share Posted August 31, 2015 I told Donafello about it. It doesnt shut down the motor when it gets hot. It tilts the pedal back with the wheel going, it doesnt stop the motor. It just forces you to slow down and stop. Link to comment Share on other sites More sharing options...
Donafello Posted August 31, 2015 Share Posted August 31, 2015 I wasnot saying it to say anything bad about the product. Just between Jason's post and and hearing that the device will cause it to stop after a long ride I decided to hold off and wait to see how this generation of 18im wheels turn out from kingsong. As soon as that 1100w motor comes out I'll buy one and sell this one second hand most likely. I know the device pedal push back is a safety feature and probably a very good one, but I plan on riding this device for long periods of time. i just thought it's a valid concern that any customer should know before making a big purchase like this and between what Jason wrote it was my decision to wait a generation and get a kingsong next go around. Link to comment Share on other sites More sharing options...
KaleOsaurusRex Posted August 31, 2015 Share Posted August 31, 2015 @Donafello Just trying to keep myself and King Song in check; you know these shutdowns are so widespread. I'm excited to hear what you think about the Gotway; I've never ridden one! Link to comment Share on other sites More sharing options...
Jason McNeil Posted August 31, 2015 Author Share Posted August 31, 2015 Thanks chaps! I'm pretty passionate about comparative & objective testing, because without it, conversations & debates can easily descend into the inane & futile, 'my Airwheel Q3 is better than your x, since Airwheel have a spec of +30 miles...' level of argument, clearly not good enough...One of the reasons why I love KS as an organisation, is that I can present this evidence, make a suggestion, like lower the voltage threshold, & usually in a couple weeks the benefits are there for all to enjoy. Have worked with three other vendors in the past & while they occasionally listen, perhaps even incorporate the product feedback/suggestion, it can be an agonizingly slow & painful process. For me, the most prescient example is with the Ninebot One: I met the Ninebot group in late October of last year & made it pretty plain I did not believe the handle pivot joint would bear up to the rigors & strains of every day use. Did they listen or investigate? Of course not, & nearly a year later the handle issue is still plaguing the product....The issue @Cloud is referring to, is almost certainly the low voltage threshold. Especially during a continuous hill climbs, when the voltage drops below the 54v threshold, the pedals tilt up & obliges the rider to dismount until the ions/chemistry attain equilibrium. Lower the threshold to 52-50v should greatly improve this—even though the voltage sags, the current does not, so the risks of it cutting out, especially with four parallel packs are minimal, there is still plenty of reserve power on tap. @HunterGuy2, the graph you provided is almost certainly not for the 18650 Li-ions, there is only one or two cells that have a capacity of 3.5Ah, whereas this chart refers to a cell with 8.5Ah. With the eLogger software it's pretty simple to calculate the Wh consumption, the avg W is provided, so it's just a matter of multiplying by time...King Song tell me they're using the LG MG1 2,900mAh battery in their 680Wh pack. The evidence/data shows that even at 1.5c (4.35A, not much by modern battery standards), we see that the voltage drops off precipitously. At this load, when it reaches the 3.25v mark, we see that the battery still has over 80% of it's capacity remaining, clearly a bit more than a couple %... The long term solution is to convince them to convert to the latest generation of cells, like the LG MH1 or HG2, both have superior performance characteristics for load, capacity, & voltage sag. http://forum.electricunicycle.org/topic/982-energy-balance-data-records/?do=findComment&comment=9839 Link to comment Share on other sites More sharing options...
Kevin Posted August 31, 2015 Share Posted August 31, 2015 Ah, I am learning new things I speak from my background in low-power electronics, where current consumption is very low and voltage sag negligible (comparable to the black line) - I guess that makes quite a big difference here!I wonder if it would be feasible to have the BMS look for rate-of-voltage-drop vs. current draw or some such, to detect when it's in the bottom end of the curve rather than having a fixed cutoff voltage. I'm also curious if Tesla has published any literature on the subject, as this seems like a problem somewhat unique to electric vehicles. Link to comment Share on other sites More sharing options...
robca Posted August 31, 2015 Share Posted August 31, 2015 I'm actually with Kale on this one.54V corresponds to a per-cell voltage of 3.375V, which is very low. Take a look at this chart of voltage vs. discharge:http://www.electronicsnews.com.au/getmedia/8ad59ccf-ada7-4c1e-b1d5-0c3e6caac755/PMFeat_Figure_1.aspxLi-Ion voltage decline is not linear, and 3.375V falls within the tail end of the curve, where the voltage rapidly degrades with further usage to the 2.5-2.8V range where the BMS cuts it off for safety reasons (the commonly used expression seems to be "may vent with flame"). In my personal experience, adjusting the cutoff from 3.375 to 3.2 or 3.1 may get you an extra few %, and below that will get you basically nothing - a few seconds worth of time if anything. It's entirely possible that originally they had the cutoff at 48V (3.0V per cell), and found this simply didn't reliably give enough time to safely force a dismount before completely running out of steam. If this was the case, I can certainly understand bumping the thresholds up at the last minute without notifying the marketing folks.However, if the actual capacity is only 500Wh that's a separate issue... how did you arrive at that figure?Do you know what battery is that for? that curve looks like a LiPo discharge curve (which I'm very familiar with), not a Li-Ion. Also the capacity is a LiPo capacity (8000mA), and the discharge at 18C (which for a 8000mA battery means a staggering 144A!) is something only LiPo can do, not normal 18650 Li-Ion... Lipo and L-Ion are completely different chemistry, completely different voltage cutoff and discharge curves... Link to comment Share on other sites More sharing options...
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