Jason McNeil Posted December 17, 2015 Share Posted December 17, 2015 As we await for the full extent of the Hoverboard fiasco to unravel, let us take stock of the possible implications on current & future developments in the Wheel World. While the immediate consequences may appear wholly negative, such as the temporary ban on taking aboard aircraft, or the public (mis)perception that electric transportation is inherently dangerous & prone to spontaneous combustion, the mid-to-longer term outcome could be the best thing to happen for the Single Electric Wheel market. From 2014-to-mid 2015 we saw a proliferation of me-too brands pop-up, all within a very small supply chain network around the Shenzhen area, 90% of these offered identical (or near identical) control-boards, battery & motors. For seasoned readers of this forum, the monotonous, but still tragic, sequence of "Where do I buy the cheapest Electric Unicycle?"---->"My x cheap Wheel is great!"--->"Had a serious accident, avoid this brand with your life!", was becoming more frequent than it should have. Even established brands suffered from unpredictable power cut-outs under hard acceleration, or when pushed beyond their top design-speed, although there has been significant advancement in power up-ratings in the past year, much work remains to be done—power cut-outs should be thought of in terms of a spectrum, e.g "Wheel x can sustain 1,500W for 10sec, while Wheel y can sustained only 600W for 10 secs.". The introduction of the Uniwheel offers some encouraging developments in safety & innovations, but in consequence of the Hoverboard mess, will other manufacturers now finally start taking safety more seriously? In previous limit testing data, acceleration cut-outs are a direct result of the battery-pack(s) being unable to provide the Wheel with sufficient peak-power to sustain the power demands of the rider. In these situations, the critical difference is how the BMS is programmed to handle when the voltage falls below the cut-off threshold: on some Wheels, it is a transient 'brown-out', where the BMS does not interrupt power flow, but the rider notices a distinctive loss in power & in most cases is able to recover. On other BMS's, it will kill power the control-board when the voltage drops below the threshold. In this situation, there is not much a rider, even an experienced one, can do to regain or maintain control of the Wheel. So what can be done? There is a very simple & relatively inexpensive solution which will make current Wheels substantially more resilient to power cut-outs, which is to use some of the latest generation Korean battery cells that offer the holy grail of both high-capacity (>3Ah) & high power (>20A). On paper at least, small improvements in the internal resistance will have a dramatic impact on maintaining pack voltage stability under demanding situations, making Wheels much safer. But why then don't we see these cells being more widely adopted? Alas, the manufacturers respond to consumer/distributor demands, which are invariably cost-cutting or the race-to-the-bottom like we've seen with the Hoverboards. The October Hong Kong Trade Shows were awash with western buyers whose entire technical vocabulary consisted of "What's the FOB price?"; the degree of ignorance, greed & hubris made these battery fire incidents all but inevitable. What the industry needs is a cull, taking out manufacturers without sufficient commitment, knowledge, or safety which will allow a handful of the serious vendors to actively develop & invest in making better quality product. As is made abundantly clear with the Boards, no one wins in a ruthless high-tech price war. Link to comment Share on other sites More sharing options...
Cranium Posted December 17, 2015 Share Posted December 17, 2015 Good write-up. I agree with you completely. I feel manufacturers need to go even farther to make these safe than to just address the batteries and BMS. The devices that self-balance require everything to be working in order to balance. This includes the batteries, BMS, control board, MOSFET, hall effect sensors and motor. A failure of any one of these can potentially cause injury and worse case death. So what can be done to make it safer as a whole? As you point out, there are too many me-too brands (great tag for them) that just want to make a buck and will copy what everyone else is doing while cutting a few corners to reduce price and get their product sold. But for the companies that care, they should start looking at the safety of Segways as the model to follow. Communication between all components and redundancy in every place you can put it. I love their model of a Safety Shutdown where something bad has happened somewhere in the system so lets provide a 10 second window to allow the rider to safely stop before shutting down. http://www.segwaysafety.com/safety-in-design#redundant Redundant batteries would increase safety (some EUs already have this). Why not have the BMS communicate with the control board and allow an over-current, under-voltage or over-temperature condition to signal the device to come to a safe (but immediate) stop rather than cutting out or causing a reduction in power output. The current state of the BMS is a big hammer approach to protect the battery with no regard to what is needing the power. There could also be redundant control boards that are each used to control 1/2 of the windings in the motor so that failure of one set of windings or control board or MOSFETs can allow a safety shutdown. And top it off with redundant sensors (gyros, accelerometers, hall-effect) that will allow the occasional erroneous reading to be filtered out and a failure to trigger a safety shutdown without a crash! The additional safety is sure to drive up costs and I think this will ultimately be the limiting factor for widespread adoption. So rather than a top down approach of making them safe, we will likely be stuck with the bottom up approach of going after the worse offenders of safety to cull them. Link to comment Share on other sites More sharing options...
lizardmech Posted December 17, 2015 Share Posted December 17, 2015 18 minutes ago, Cranium said: Good write-up. I agree with you completely. I feel manufacturers need to go even farther to make these safe than to just address the batteries and BMS. The devices that self-balance require everything to be working in order to balance. This includes the batteries, BMS, control board, MOSFET, hall effect sensors and motor. A failure of any one of these can potentially cause injury and worse case death. So what can be done to make it safer as a whole? As you point out, there are too many me-too brands (great tag for them) that just want to make a buck and will copy what everyone else is doing while cutting a few corners to reduce price and get their product sold. But for the companies that care, they should start looking at the safety of Segways as the model to follow. Communication between all components and redundancy in every place you can put it. I love their model of a Safety Shutdown where something bad has happened somewhere in the system so lets provide a 10 second window to allow the rider to safely stop before shutting down. http://www.segwaysafety.com/safety-in-design#redundant Redundant batteries would increase safety (some EUs already have this). Why not have the BMS communicate with the control board and allow an over-current, under-voltage or over-temperature condition to signal the device to come to a safe (but immediate) stop rather than cutting out or causing a reduction in power output. The current state of the BMS is a big hammer approach to protect the battery with no regard to what is needing the power. There could also be redundant control boards that are each used to control 1/2 of the windings in the motor so that failure of one set of windings or control board or MOSFETs can allow a safety shutdown. And top it off with redundant sensors (gyros, accelerometers, hall-effect) that will allow the occasional erroneous reading to be filtered out and a failure to trigger a safety shutdown without a crash! The additional safety is sure to drive up costs and I think this will ultimately be the limiting factor for widespread adoption. So rather than a top down approach of making them safe, we will likely be stuck with the bottom up approach of going after the worse offenders of safety to cull them. I hope to be able to do this soon, I'm trying to put together a custom control board with canbus+ other IO, open firmware and a few other things. If I can succeed getting that made I can then move on to a BMS with a MCU and canbus to communicate plenty of data. Redundant gyro and motor control should be as simple as linking two of the boards together and using that special motor winding. Link to comment Share on other sites More sharing options...
ConjurMan Posted December 17, 2015 Share Posted December 17, 2015 I am consistently impressed with the brainpower of the folks on this forum. I hope that the EUC manufacturers will consider this input as they are considering new designs. If not, they should. I'd certainly rather pay more up front for a safe wheel then to get a cheap price and pay later, with injuries (or worse). Link to comment Share on other sites More sharing options...
Jason McNeil Posted December 17, 2015 Author Share Posted December 17, 2015 44 minutes ago, Cranium said: should start looking at the safety of Segways as the model to follow. Communication between all components and redundancy in every place you can put it. I love their model of a Safety Shutdown where something bad has happened somewhere in the system so lets provide a 10 second window to allow the rider to safely stop before shutting down. The current state of the BMS is a big hammer approach to protect the battery with no regard to what is needing the power. True, but using a probabilistic model, nearly every accident that I have seen here (that is not operator error) is a direct result of insufficient battery/power (or poor QC with firmware releases). Battery power is a low hanging fruit that's easy to solve here & now. Isn't there an argument that the Segway's limited redundancy was not really a virtue but a reflection of the state of technology at the time. MTBF of critical solid state components today are extremely reliable & that in a probabilistic world the integration of less than perfect redundant systems will make the system less safe—the KISS principle. Are there any examples of MOSFET redundancy today? IPS are the only manufacturer, that I'm aware of, that make use of 12 on their control-board, but I really don't know if provides any actual redundancy for a channel in the H Bridge. Link to comment Share on other sites More sharing options...
OliverH Posted December 17, 2015 Share Posted December 17, 2015 10 minutes ago, Jason McNeil said: True, but using a probabilistic model, nearly every accident that I have seen here (that is not operator error) is a direct result of insufficient battery/power (or poor QC with firmware releases). Battery power is a low hanging fruit that's easy to solve here & now. Isn't there an argument that the Segway's limited redundancy was not really a virtue but a reflection of the state of technology at the time. MTBF of critical solid state components today are extremely reliable & that in a probabilistic world the integration of less than perfect redundant systems will make the system less safe—the KISS principle. Are there any examples of MOSFET redundancy today? IPS are the only manufacturer, that I'm aware of, that make use of 12 on their control-board, but I really don't know if provides any actual redundancy for a channel in the H Bridge. But IPS made bridging of the MOSFETs? The motor in an IPS still has 3 phases. H bridge or how is it called? The need of redundancy can be required by gov. You can calculate in the safety world. A colleague has studied safety stuff. We had some nice talks on doing calculations to prevent the need of redundancy (requirement by gov over here). She said: Not possible. And having redundancy you need to show that a blown MOSFET will not harm the redundancy to proper work. Which is impossible with current mainboards (blocking the wheel or need heavy force to turn it). Link to comment Share on other sites More sharing options...
Cranium Posted December 17, 2015 Share Posted December 17, 2015 29 minutes ago, Jason McNeil said: True, but using a probabilistic model, nearly every accident that I have seen here (that is not operator error) is a direct result of insufficient battery/power (or poor QC with firmware releases). Battery power is a low hanging fruit that's easy to solve here & now. Isn't there an argument that the Segway's limited redundancy was not really a virtue but a reflection of the state of technology at the time. MTBF of critical solid state components today are extremely reliable & that in a probabilistic world the integration of less than perfect redundant systems will make the system less safe—the KISS principle. Are there any examples of MOSFET redundancy today? IPS are the only manufacturer, that I'm aware of, that make use of 12 on their control-board, but I really don't know if provides any actual redundancy for a channel in the H Bridge. I agree, the batteries are low hanging fruit. Incremental steps to make things better now does put us in a safer condition than waiting for a complete re-design. I would have to disagree with Segway's approach being a reflection of the state of technology. While I'm sure in the earlier days it was much more utilized, it still doesn't eliminate the need. In drive-by-wire cars, there is redundancy. In fly-by-wire planes (and spacecraft), there is redundancy. If the failure of one component could cause serious injury or death, we are rolling the dice and hoping that it doesn't fail and if it does, hoping it doesn't result in the worse case scenario. There are limitations to redundancy such as you can't have redundant wings on a plane but there is one manufacturer that is even accounting for a wing falling off by putting a parachute on the chassis of plane if this were to happen. It has saved lives before even though the likelihood of something catastrophic happening like that is extremely low. It is just good engineering. Balancing redundancy with cost is always going to be a tough discussion. How much is a life worth? How about a limb? What are we willing to pay to keep us safe[r]? There will be no answers of this here, that's for sure. But the KISS principle does not address safety directly. Simple is not always better. The simplest & safest model should be the choice and with your suggestion of improving the battery design, this is moving us in this direction. Ninebot One E+ and P uses 12 MOSFETs (I can only speak for these two but maybe all of them do). But as you pointed out, these can't be considered redundant. There are 6 pairs of MOSFETs so each MOSFET is sharing its load with another in parallel. This does increase reliability but in the event of an open short, it does nothing to help keep the EU vertical. If you had a motor with redundant windings and control boards with MOSFETs driving these, you could have the failure of a winding set or a failure of a MOSFET in one of the boards and you would still be able to safely shut down. Segway is the only design that I know of that does this. Link to comment Share on other sites More sharing options...
Keith Posted December 17, 2015 Share Posted December 17, 2015 1 hour ago, ConjurMan said: I'd certainly rather pay more up front for a safe wheel then to get a cheap price and pay later, with injuries (or worse). Interestingly, the key "negatives" being expressed about the Uniwheel on this forum so far seem to be its price versus performance. Yet the Uniwheel is clearly being designed with safety as a key parameter and, as far as I can see, has the safest batteries on the electric wheel market. I personally would read that as most wouldn't actually consider paying much more for a safer wheel? Let's hope I'm wrong. Going back to Jason's original post, my gut feeling is that the brown stuff will stick to all of us as the more rabid elements of the press (certainly in the UK) latch on to Hoverboard failures over the Christmas silly season. Whether, longer term, this will result in better quality from fewer more safety conscious suppliers remains to be seen. It certainly would if Uniwheel do become successful. I would agree with Jason that Battery operational safety, particularly good quality cells with the lowest possible internal resistance with BMS that favour rider safety over cell life is certainly (IMHO) the simplest (but far from cheapest) option. The discussion drifted to other safety improvements. From personal experience over the years with electric model aircraft, FET's seem to be prone to failing short circuit more often than open circuit so FET's in parallel aren't going to help and are there to handle higher current. They would have to be in series or series/parallel to have any redundancy. Redundancy in motor coils with two controllers might help but a sudden drop to half power or less might give the same result as a total failure if unexpected. In signing off its worth noting that twin engined light aircraft have a higher number of accidents (per number in service) than singles as there is twice the chance of failure and out of practice pilots get caught out when it happens. Oh and as for parachutes, the last plane crash inquest I read concluded that the forced landing had been survivable but the occupants were killed by the parachute rocket motor going off on impact. Sometimes what seems like the safest engineering solution actually isn't. Link to comment Share on other sites More sharing options...
Colestien Posted December 17, 2015 Share Posted December 17, 2015 I should add here, These systems are not failing, they are doing exactly what they are designed to do. Redundancy is good when you have a system that works. It is insurance against the unknown or Murphy's law in general. When you have a system that fails, and you use redundancy to help the system fail less..... That is still a fail. The concept "KISS" does not have to mean only simple. It means address the system with what it needs and don't go crazy about it. KISS should help us focus on getting the Power system communicating with the Control circuit. While working on the Software that allows it all to work safely. What KISS doesn't mean is spending time developing something like the "airbag" suit as we saw in the movie Tomorrowland. Of course that will be good when my sons Grandchlidren have these things flying but not yet. Link to comment Share on other sites More sharing options...
dmethvin Posted December 17, 2015 Share Posted December 17, 2015 32 minutes ago, Keith said: Interestingly, the key "negatives" being expressed about the Uniwheel on this forum so far seem to be its price versus performance. Yet the Uniwheel is clearly being designed with safety as a key parameter and, as far as I can see, has the safest batteries on the electric wheel market. I personally would read that as most wouldn't actually consider paying much more for a safer wheel? Let's hope I'm wrong. The problem I see with the Uniwheel is that its performance/endurance is too low for the enthusiast, but its price is too high for the casual user who just wants to explore the EUC market. They would be better off building a more expensive wheel IMO. That is the strategy Tesla followed for example, they built their high-end stuff first to establish their reputation. And there must be some people out there willing to pay for quality, the Solowheel Xtreme is more than $2,000! Link to comment Share on other sites More sharing options...
Cranium Posted December 17, 2015 Share Posted December 17, 2015 1 hour ago, Keith said: Oh and as for parachutes, the last plane crash inquest I read concluded that the forced landing had been survivable but the occupants were killed by the parachute rocket motor going off on impact. Sometimes what seems like the safest engineering solution actually isn't. Cherry picking one negative outcome out of so many more positive outcomes as an example that engineering didn't increase safety is absurd. It is an unquestionable fact that lives have been saved by having this redundancy in safety. It doesn't have to be 100% issue free to be considered safer. The numbers speak for themselves. http://airfactsjournal.com/2015/02/fatal-cirrus-crashes-way-thank-parachute/ If you are referring to this incident (which happened just down the road from me), you are not correct in your assessment for including it in this argument. There was nothing in any credible report that suggested the parachute killed the occupants or that it had anything to do with the crash. There was no final determination as to why the parachute was deployed right before the crash and in this incident, it is irrelevant because it would not have helped regardless because it was at too low of an altitude when deployed. Sorry for going off topic guys. Link to comment Share on other sites More sharing options...
Gimlet Posted December 17, 2015 Share Posted December 17, 2015 3 hours ago, dmethvin said: The problem I see with the Uniwheel is that its performance/endurance is too low for the enthusiast, but its price is too high for the casual user who just wants to explore the EUC market. They would be better off building a more expensive wheel IMO. That is the strategy Tesla followed for example, they built their high-end stuff first to establish their reputation. And there must be some people out there willing to pay for quality, the Solowheel Xtreme is more than $2,000! I think you're wrong dmethvin. High speed causes problems in keeping a large enough power margin for safety, 20/22kph is a reasonably fast speed for general use, quite comfortable for long distance travel without pushing too close to the achievable power limits and compromising safety. As far as batteries are concerned, it pains me to have to carry the weight of enough batteries to theoretically carry me four or five times as far as I actually want to go just so that I can reliably climb steep hills at the end of my ride and reliably keep me upright when the going gets rough. Only real world testing of alternative battery technologies can let you realise their capabilities. Link to comment Share on other sites More sharing options...
edwin_rm Posted December 18, 2015 Share Posted December 18, 2015 As someone who owns a SoloWheel Xtreme, the absolute safest EUC available, it was a complete waste of money. It lacks range! What good is a battery that can't catch fire if it is small and gets depleted quickly? Link to comment Share on other sites More sharing options...
playdad Posted December 18, 2015 Share Posted December 18, 2015 1 hour ago, edwin_rm said: As someone who owns a SoloWheel Xtreme, the absolute safest EUC available, it was a complete waste of money. It lacks range! What good is a battery that can't catch fire if it is small and gets depleted quickly? You live a longer life... Getting off and carrying the weight of the wheel around provides extra health benefits through exercise. Since you live a longer life... you have more time to spend walking too - not to mention its a good stress relief and stress is a major cause of health problems. Unless you live in China (like me) and walking can kill you via pollution and reckless driving. ps. this was meant to be ironic and a joke! Link to comment Share on other sites More sharing options...
checho Posted December 18, 2015 Share Posted December 18, 2015 I think lifepo4 batteries are good, and not catching on fire it is a good thing. The reason the solowheel battery has a poor range it is not because it is a lifepo4 battery, it is because it is a small battery pack, if it was li-on and the same size you would still get a equally poor range. The only problem I can see with lifepo4 batteries is that they are a little bit more expensive than li-on batteries. For the price the solowheel has it should have a much larger battery pack. Link to comment Share on other sites More sharing options...
esaj Posted December 18, 2015 Share Posted December 18, 2015 10 hours ago, edwin_rm said: As someone who owns a SoloWheel Xtreme, the absolute safest EUC available, it was a complete waste of money. It lacks range! What good is a battery that can't catch fire if it is small and gets depleted quickly? 2 hours ago, checho said: I think lifepo4 batteries are good, and not catching on fire it is a good thing. The reason the solowheel battery has a poor range it is not because it is a lifepo4 battery, it is because it is a small battery pack, if it was li-on and the same size you would still get a equally poor range. The only problem I can see with lifepo4 batteries is that they are a little bit more expensive than li-on batteries. For the price the solowheel has it should have a much larger battery pack. Some time back we actually found out that the "newer" Solowheel Classic (S300 designation?) and Solowheel Xtreme neither use Lifepo4's anymore, but Sony VC3's. So the safety of the battery is about the same as with other brands using high quality cells. Only the "old" classic uses LiFePo4. http://forum.electricunicycle.org/topic/601-energy-efficiency-of-euc/?do=findComment&comment=6386 From http://solowheel.com/product/xtreme : VC3 battery Solowheel uses the highest-quality battery available, providing reliable high performance and safety. The VC3 battery is non-flammable and non-explosive. Each battery cell has independent dual protection. So they're cells with internal protection, I believe the chemistry is LiMn (NMC). Link to comment Share on other sites More sharing options...
playdad Posted December 18, 2015 Share Posted December 18, 2015 Well, then that negates any so called safety benefit of any shorter range after all. Link to comment Share on other sites More sharing options...
Thumper0511 Posted December 18, 2015 Share Posted December 18, 2015 Does anyone know what type of battery the Ninebot 1E+ uses and who manufactures it.... and generally if its safe/reliable? Link to comment Share on other sites More sharing options...
Donafello Posted December 18, 2015 Share Posted December 18, 2015 3 minutes ago, Thumper0511 said: Does anyone know what type of battery the Ninebot 1E+ uses and who manufactures it.... and generally if its safe/reliable? It seems to be one of the more popular euc and is reliable Link to comment Share on other sites More sharing options...
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