Jason McNeil Posted February 8, 2016 Share Posted February 8, 2016 When seeing the article about the proposed EU technical standard, it prompted me into action to assemble a list of operating characteristics & component specifications that we as a group are probably best qualified to suggest to manufacturers & legislative bodies. I'm not an Engineer by training, the draft spreadsheet is just an early draft & needs a great deal of more work; I'm confident that the combined experience/expertise/brain-power of the forum can produce a good result. Please feel free to add/modified/comments https://drive.google.com/open?id=0B-WCZQc2gfJjb1dRcEM3aGdrb3c Link to comment Share on other sites More sharing options...
esaj Posted February 8, 2016 Share Posted February 8, 2016 That's a good list, here's a couple of things that sprung into mind reading it: I'm not sure if you can demand "voltage drop of maximum of 0.3V / cell from 1A discharge", as the voltage drop isn't linear all the way (becomes a lot higher when the batteries are more empty) and outside things also affect it (like temperature). I know the Firewheel voltage drop with 3 parallel custom packs was something like 5-6 volts (0.3125-0.375V per cell) under stress just before the battery warning (from around 53-54V "rest" voltage -> 47-48V, I think the warning triggers once the voltage drops below 47V momentarily). Maybe maximum allowed internal resistance could work better? 10A continuous discharge sounds very reasonable, knowing what sort of power spikes are needed every now and then, but a inimum 4A charge rate per cell(-series) sounds somewhat excessive. Not to say that possibility to do quick charge every now and then wouldn't be nice. It could also leave out otherwise viable cells just because they cannot withstand that high charge currents (>1C for all currently available cells). As for the connector, I'm not sure why the wheels use GX16-3 in the first place, as they only need 2 pins, but don't know that much about connectors to suggest anything better. Furthermore, GX16-3 is rated for 5A; using 4A charge rate per one series of cells would mean you couldn't charge two or more series with full 4A per series anyway (the connector couldn't take it at 8A or more). Thick wires is a good idea, but one place where they are fairly thing (IMHO) are the motor phase-wires. Not much use bringing the power into mainboard bridge even with an inch thick cable, if the phase wires are something like 20AWG? Not so sure if the motor winding should be regulated, my (limited) understanding is that it is (one way?) used to control the torque/max speed-ratio, limiting it could lead to no high torque / no high-speed wheels (don't remember which way it goes, is lower number of windings high speed or high torque?) About water resistance, the IP-certification is nice if any of the wheels actually adhered to it, despite claiming IP65 20 meter visibility sounds fairly low for lights, imho. A car or bicycle traveling towards you at 36km/h is moving 10 meters per seconds, say you'd come towards it at 20km/h, that would leave about 1.3 seconds of reaction & braking/evading time for both if they'd see you at 20 meters (and you'd mistakenly thought they'd already seen you) Also, weather conditions and light height are going to affect this (there's a minimum height the bicycle lights must be installed in Finnish law, don't remember what it was though). Parallel MOSFET count could be upped instead of using higher specced' fets? What I've been wondering lately is that they use 2 or 3 parallel mosfets in the BMS discharge side yet only single ones in the drive bridges (granted that the drive bridge mosfets are "on" only around 1/3rd of the time and off otherwise). Not that "over-speccing" probably would hurt even with more paralleled mosfets. Price/space or PCB/heatsink size issue maybe? Excessive braking power handling with large resistor might a problem (size/weight wise), the 900W resistors I've seen were pretty large (over foot long, don't remember the weight, several kilos? ). Multiple 100W power resistors in parallel probably could work (but would still need a very large heat sink)? Water cooling? Link to comment Share on other sites More sharing options...
Nevin@Tec-toyz.com Posted February 9, 2016 Share Posted February 9, 2016 6 hours ago, Jason McNeil said: When seeing the article about the proposed EU technical standard, it prompted me into action to assemble a list of operating characteristics & component specifications that we as a group are probably best qualified to suggest to manufacturers & legislative bodies. I'm not an Engineer by training, the draft spreadsheet is just an early draft & needs a great deal of more work; I'm confident that the combined experience/expertise/brain-power of the forum can produce a good result. Please feel free to add/modified/comments https://drive.google.com/open?id=0B-WCZQc2gfJjb1dRcEM3aGdrb3c Hey Jason, what was that MCM4 Wh that you were riding? Sorry, off topic ?. I thought about it while going through your list. Link to comment Share on other sites More sharing options...
Cranium Posted February 9, 2016 Share Posted February 9, 2016 Comments made on many line items in the sheet. I couldn't edit your sheet for some reason to add comments so copied it and added them. https://docs.google.com/spreadsheets/d/1O6gifzQkv2ieaRBFxNV7UrqUlLVGLIrACswfbjPXBSM/edit?usp=sharing This UL requirement document would be great to get our hands on: http://ulstandards.ul.com/standard/?id=2271 But they want $402 for a downloadable PDF. I never realized the UL was such a money maker! LOL Link to comment Share on other sites More sharing options...
Shoe73 Posted February 9, 2016 Share Posted February 9, 2016 I saw the line about 'power on, no audible' and while I do find the power-on beep annoying, it is probably important to have. The speaker is usually used to warn the rider of low battery, overheating, etc. If you don't have the power-on beep, when the speaker stops working on your wheel you will not know about it till it's too late. It's good to automatically test that functionality on startup. Link to comment Share on other sites More sharing options...
lizardmech Posted February 9, 2016 Share Posted February 9, 2016 Mofets are very difficult to suggest, depending on the design of the board and mosfet package you may only be able to use 5% of their listed rating. While another design may be able to use 70% but because it has less mosfets it would be classed as inferior based on theoretical mosfet ratings alone. Link to comment Share on other sites More sharing options...
Chriull Posted February 9, 2016 Share Posted February 9, 2016 1 hour ago, lizardmech said: Mofets are very difficult to suggest, depending on the design of the board and mosfet package you may only be able to use 5% of their listed rating. While another design may be able to use 70% but because it has less mosfets it would be classed as inferior based on theoretical mosfet ratings alone. Quote ... Parallel MOSFET count could be upped instead of using higher specced' fets? What I've been wondering lately is that they use 2 or 3 parallel mosfets in the BMS discharge side yet only single ones in the drive bridges (granted that the drive bridge mosfets are "on" only around 1/3rd of the time and off otherwise). Not that "over-speccing" probably would hurt even with more paralleled mosfets. Price/space or PCB/heatsink size issue maybe? The specification of the MOSFETs imho cannot be taken for the recommended standard - as written above, recognise it depends on the overall design. You can take the "best" Mosfets, but without proper cooling they will burn anyway... And the firmware has to be adequate, too - any EUC will kill their MOSFETs if it gets "stuck" and the firmware does not recognise this situation... (and the BMS does not cut out) That's like with cars - the enginge, gearbox, suspension, etc have to fit together. You cannot specify one alone - the whole design has to be adequate. Maybe the easiest way is to specify some sort of "test parkour" on a dynamometer a EUC has to survive/manage. There already exist enough standards for electric cars, bikes, etc. which could/should be adapted for EUCs? Like already many manufacturers state a IP65 (which would be a nice minimun standard) - but its nowhere certified or controlled... Quote Excessive braking power handling with large resistor might a problem (size/weight wise), the 900W resistors I've seen were pretty large (over foot long, don't remember the weight, several kilos? ). Multiple 100W power resistors in parallel probably could work (but would still need a very large heat sink)? Water cooling? "Excess energy protection" is by now not implemented in any EUC. Many/some have already problems getting rid of the excess heat from the motor driver (Mosfets) - and the breaking power needed to be dissipated is somwhere in the range of 1-3 kW - it's not really sexy to put a hotplate on an EUC Could be the biggest problem for a safe EUC. By now the battery packs are just (over)stressed (which in the best case just reduces their life time), some just stop breaking or burn their Mosfets... Edit: Dynamic Breaking (burning the excess energy in an external resistor) is not implemented with current EUCs, but some kind of plugging breaking could be implemented, where the energy is dissipated in the motor coils (and Mosfets). Link to comment Share on other sites More sharing options...
lizardmech Posted February 9, 2016 Share Posted February 9, 2016 4 minutes ago, Chriull said: Maybe the easiest way is to specify some sort of "test parkour" on a dynamometer a EUC has to survive/manage. There already exist enough standards for electric cars, bikes, etc. which could/should be adapted for EUCs? Like already many manufacturers state a IP65 (which would be a nice minimun standard) - but its nowhere certified or controlled... Maybe require 6 hours on a dyno at max cruise speed with a load as if it had a rider. You can measure control board, battery and motor temp all in one test. Link to comment Share on other sites More sharing options...
RidingInTheRain Posted February 9, 2016 Share Posted February 9, 2016 9 hours ago, Shoe73 said: I saw the line about 'power on, no audible' and while I do find the power-on beep annoying, it is probably important to have. The speaker is usually used to warn the rider of low battery, overheating, etc. If you don't have the power-on beep, when the speaker stops working on your wheel you will not know about it till it's too late. It's good to automatically test that functionality on startup. While I agree I would point out that this should probably be redefined to mean: beep yes, but no voice output or something like that. I agree that testing the warning sound / general speaker hardware should be done on startup. But please let us at least deactivate voice output. Link to comment Share on other sites More sharing options...
Shoe73 Posted February 9, 2016 Share Posted February 9, 2016 1 hour ago, xamino said: While I agree I would point out that this should probably be redefined to mean: beep yes, but no voice output or something like that. I agree that testing the warning sound / general speaker hardware should be done on startup. But please let us at least deactivate voice output. Yeah, who decided voice output was desirable in the first place? I'm very glad my wheels don't have it. Link to comment Share on other sites More sharing options...
Jason McNeil Posted February 9, 2016 Author Share Posted February 9, 2016 Read somewhere that the way circuitry is designed for high-reliability systems is that a design team evaluates MTBF on a statistical component basis which is the basis for the aggregate system's risk failure. It would be terrific if Manufacturers actually did testing to destruction analysis on each of the primary elements of the battery pack, control-board & motor & made the results publicly available. I very much doubt that today there is any rigorous method to their claimed power ratings. The question of redundancy has been brought up before: in current designs there are not many components that can suffer from partial failure resulting in degraded, but not catastrophic, failure. I think the challenge will be incorporating some fault-tolerance that has a meaningful statistical impact on reducing the risk but does have a negative impact on the either the weight or cost of the Wheel. With battery pack parallelization, the Wheel should be able to work even if a single cell in a series fails, but can the same be said, for example, if a permanent magnet in the rotor becomes dislodged, or a hall sensor misreading? Can MOSFETs in a half-bridge be configured for load-balancing & if so would it really be any benefit? 11 hours ago, Chriull said: already exist enough standards for electric cars, bikes, etc. which could/should be adapted for EUCs? @Cranium found a presentation which talks a bit about the UL 2271 standard. It seems to describe the pack & it's safety, but where the properties of the individual cells are known, wonder how beneficial this would be: http://www.sae.org/events/gim/presentations/2010/priyatabaddor.pdf "Light Electric Vehicle (LEV) – A small on-road or off-road vehicle that uses electricity as its sole source of energy for motive power. LEV’s cover, but are not limited to the following vehicles: electric bicycles, electric scooters, and electric wheel chairs Covers rechargeable batteries and battery packs for use in light electric vehicles (LEVs) as defined in this standard, with a maximum output of 60 V, DC. " TUV look like they're the most qualified to undertake this sort of testing but it's clear that any sort of Wheel standard would have to be written from the ground up—a motor failure on an eBike is of no consequence when compared to a single Wheel. Also the current eBike legislation is back to front for our purposes—for eBikes the objective testing is to ensure the power is limited (below 250W sustained) which is exactly the opposite of the needs of the Wheel. http://www.datei.de/public/extraenergy/2012_Veranstaltungen/120306_Taipei/BATSO_report_from_TUV_Rheinland_Shenzhen.pdf 21 hours ago, esaj said: I'm not sure if you can demand "voltage drop of maximum of 0.3V / cell from 1A discharge", as the voltage drop isn't linear all the way (becomes a lot higher when the batteries are more empty) I think voltage drop below the minimum threshold is safety-issue #1. Considered IR as a benchmark, but it only describes the properties of the cell. Maybe what we want is an acceptable Ω value inclusive of battery cells, wires, BMS, controlboard? 21 hours ago, esaj said: 4A charge rate per cell(-series) sounds somewhat excessive 4A fast charge rate is pretty standard now on +>15A cells. 21 hours ago, esaj said: not sure why the wheels use GX16-3 in the first place, as they only need 2 pins Agreed, yet it should be idiot proof, physically impossible to insert in the wrong way round. 21 hours ago, esaj said: [windings] used to control the torque/max speed-ratio Yes, but some guidance should be given to manufacturers on appropriate numbers for a given Wheel diameter, number of stator poles, max speed & weight specifications. 21 hours ago, esaj said: 20 meter visibility sounds fairly low for light True, set a low bar here, on the one hand we don't want to dazzle oncoming traffic with 20,000 lumens, but still have good visibility. A couple ideas: 1) Gimbal stabilized headlight: where the pitch angle can be controlled through the App. As you're riding along, the headlight will move relative to the position of the Wheel & provide a stabilized path (might be too complex) 2) Adaptive brightness linked to the speed: as you increase velocity, the LED headlight gets brighter 3) Brightness settings controlled through the App. As an alternative to the integrated option, the spec could have something about a mount that the owner can attach an external bike torch. 21 hours ago, esaj said: Parallel MOSFET count could be upped instead of using higher specced' fets? I'm not aware of any good quality MOSFET failures such as the type @Cranium compared in his 9B1 P post. The 100N8F6 has a massive safety margin. Wouldn't it make more sense to package the control-board with these components than some produced by some factory with questionable QC processes? 21 hours ago, esaj said: Excessive braking power handling with large resistor might a problem (size/weight wise), the 900W resistors I've seen were pretty large (over foot long, don't remember the weight, several kilos? Was thinking about a small heating element here. Wrote to @DaveThomasPilot (who's an Electronic's Engineer) about this a couple weeks back, where a regulator would shunt excess regen to the element. Since it would only be momentary burst, it should be ok, another option is add a ducted fan based ventilation for shaft to cool the element. Link to comment Share on other sites More sharing options...
Chriull Posted February 10, 2016 Share Posted February 10, 2016 15 hours ago, Jason McNeil said: Read somewhere that the way circuitry is designed for high-reliability systems is that a design team evaluates MTBF on a statistical component basis which is the basis for the aggregate system's risk failure. It would be terrific if Manufacturers actually did testing to destruction analysis on each of the primary elements of the battery pack, control-board & motor & made the results publicly available. I very much doubt that today there is any rigorous method to their claimed power ratings. Professional design and thorough testing would be a real benefit! Quote The question of redundancy has been brought up before: in current designs there are not many components that can suffer from partial failure resulting in degraded, but not catastrophic, failure. I think the challenge will be incorporating some fault-tolerance that has a meaningful statistical impact on reducing the risk but does have a negative impact on the either the weight or cost of the Wheel. With battery pack parallelization, the Wheel should be able to work even if a single cell in a series fails, but can the same be said, for example, if a permanent magnet in the rotor becomes dislodged, or a hall sensor misreading? Before implementing some fault-tolerance imho point 1 (professional design and thorough testing) has to be fullfilled - or you do not know the critical components and add unnecessary complexity to a "faulty" system. There is no use in replacing a failed system by the same/a similar faulty system and let this fail again... Quote Can MOSFETs in a half-bridge be configured for load-balancing & if so would it really be any benefit? Mosfets used by now in the EUCs should be fine. Maximum peak power should be below 3kW (shown from the data logging here in the forum). For 50-60V that implies a current of 50-60A... Quote ... I'm not aware of any good quality MOSFET failures such as the type @Cranium compared in his 9B1 P post. The 100N8F6 has a massive safety margin. Wouldn't it make more sense to package the control-board with these components than some produced by some factory with questionable QC processes? ...which is well within the specifications for continous currents. Both Mosfets could even handle peak currents of 300+A. (Pulse width limited by safe operating area) With this 3kw load the mosfets have to dissipate about 50W (R DSon (internal resistance) is for both types at higher temperatures more like 15mOhm) - so roughly 8W by mosfet. Which both types can easily handle - if they are _properly_ cooled. Which is unfortionately not the case - as long as there is no sufficient thermal handling it does not (really) matter if you put some mosfets in parellel or try something else... A bigger thermal problem is regenerative breaking, where about similar currents flow through the invers diodes of the mosfets and there they have to dissipate even more power. This also could be well handled by using low forward voltage diodes or using the mosfets as ideal diodes (could be implemented by the mosfet driver - or maybe actually is in some controllers...) Link to comment Share on other sites More sharing options...
OliverH Posted February 10, 2016 Share Posted February 10, 2016 15 hours ago, Jason McNeil said: Read somewhere that the way circuitry is designed for high-reliability systems is that a design team evaluates MTBF on a statistical component basis which is the basis for the aggregate system's risk failure. It would be terrific if Manufacturers actually did testing to destruction analysis on each of the primary elements of the battery pack, control-board & motor & made the results publicly available. I very much doubt that today there is any rigorous method to their claimed power ratings. @CraniumThe question of redundancy has been brought up before: in current designs there are not many components that can suffer from partial failure resulting in degraded, but not catastrophic, failure. I think the challenge will be incorporating some fault-tolerance that has a meaningful statistical impact on reducing the risk but does have a negative impact on the either the weight or cost of the Wheel. With battery pack parallelization, the Wheel should be able to work even if a single cell in a series fails, but can the same be said, for example, if a permanent magnet in the rotor becomes dislodged, or a hall sensor misreading? Can MOSFETs in a half-bridge be configured for load-balancing & if so would it really be any benefit? I think the way to follow and answer this question is ISO 26262 with the QM or ASIL A-D levels (like SIL wit IEC 61508). But we need to look what CEN/TC 354/WG 4 defines. I've contacted AFNOR and DIN - waiting for an reply. What ever happens the skills needed (manufacturer/ distributor) will rise dramatically in the next 6-12 month. It's not any more change you mind it's rude awakening. Safety is the problem of low sales and at the same time the key to volume and street legal. We're in contact with a manufacturer (one more try) to get this things sorted out. CEN/TC 354/WG 4 came just in time. Depending on what are the technical requirements and if the European countries enforce this voluntary standard this can block imports at customs. It's like CE label and the certification of the product. But CEN/TC 354/WG 4 defines the same level for testing in all countries (harmonization of standards). What we need in the next step: PLEV as a vehicle category in all European countries. Some has to do it from source other can extend/ harmonize existing regulation (Germany: MobHV, Switzerland: VTS). Link to comment Share on other sites More sharing options...
Jurgen Posted February 10, 2016 Share Posted February 10, 2016 On 9-2-2016 at 9:07 AM, Chriull said: The specification of the MOSFETs imho cannot be taken for the recommended standard - as written above, recognise it depends on the overall design. You can take the "best" Mosfets, but without proper cooling they will burn anyway... And the firmware has to be adequate, too - any EUC will kill their MOSFETs if it gets "stuck" and the firmware does not recognise this situation... (and the BMS does not cut out) That's like with cars - the enginge, gearbox, suspension, etc have to fit together. You cannot specify one alone - the whole design has to be adequate. Maybe the easiest way is to specify some sort of "test parkour" on a dynamometer a EUC has to survive/manage. There already exist enough standards for electric cars, bikes, etc. which could/should be adapted for EUCs? Like already many manufacturers state a IP65 (which would be a nice minimun standard) - but its nowhere certified or controlled... "Excess energy protection" is by now not implemented in any EUC. Many/some have already problems getting rid of the excess heat from the motor driver (Mosfets) - and the breaking power needed to be dissipated is somwhere in the range of 1-3 kW - it's not really sexy to put a hotplate on an EUC Could be the biggest problem for a safe EUC. By now the battery packs are just (over)stressed (which in the best case just reduces their life time), some just stop breaking or burn their Mosfets... Edit: Dynamic Breaking (burning the excess energy in an external resistor) is not implemented with current EUCs, but some kind of plugging breaking could be implemented, where the energy is dissipated in the motor coils (and Mosfets). not 100% of braking should be regenerative, you could ad electromechanical braking as a support and for redundancy Link to comment Share on other sites More sharing options...
Pilotguy Posted February 11, 2016 Share Posted February 11, 2016 I think rather than specify the detailed intricacies of how to solve the various problems . It better allows for various avenues of development if one specifies the desired result . A safe 5 second shutdown mode for any system failure A redundant backup system for the shutdown mode pedal tilt back a plug in safety line a person can attach to their belt that will immediately turn the unit off when it becomes unplugged in a fall or a reliable way for the unit to sense it no longer has a rider so it can shut off and not do the devil dance ! I would be happy if all units had the basic features listed above . Link to comment Share on other sites More sharing options...
Jason McNeil Posted February 15, 2016 Author Share Posted February 15, 2016 This is quite interesting: Universal Labs have announced a testing procedure for the much maligned 'Hoverboards'. I'm going to get in touch with the testing team to discuss the possibility of a collaboration. http://ulstandards.ul.com/standard/?id=2272&edition=1&doctype=outline Outline Title Page Table of Contents Body INTRODUCTION 1 Scope 2 Components 3 Units of Measurement 4 Undated References 5 Glossary CONSTRUCTION 6 Non-Metallic Materials 7 Metallic Parts Resistance to Corrosion 8 Enclosures 9 Wiring and Terminals 10 Chargers 11 Fuses 12 Lighting 13 Electrical Spacings and Separation of Circuits 14 Insulation Levels and Protective Grounding 15 Protective Circuits and Safety Analysis 16 Cells 17 Motors 18 Manufacturing and Production Line Testing PERFORMANCE 19 General 20 Tolerances 21 Post Test Cycle 22 Results Criteria ELECTRICAL TESTS 23 Overcharge Test 24 Short Circuit Test 25 Overdischarge Test 26 Temperature Test 27 Imbalanced Charging Test 28 Dielectric Voltage Withstand Test 29 Isolation Resistance Test MECHANICAL TESTS 30 Vibration Test 31 Shock Test 32 Crush Test 33 Drop Test 34 Mold Stress Relief Test 35 Motor Overload Test 36 Motor Locked Rotor 37 Strain Relief Tests (Cord Anchorages) 37.1 General 37.2 Strain relief pull test 37.3 Push-back test ENVIRONMENTAL TESTS 38 Water Exposure Tests 38.1 IPX4 Code rating 38.2 Partial immersion 39 Thermal Cycling Test 40 Label Permanence Test MARKINGS 41 General INSTRUCTIONS 42 General Link to comment Share on other sites More sharing options...
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