hyiu00 Posted October 20, 2016 Share Posted October 20, 2016 There is a safety difference between a self-balancing vehicle like a euc versus a e-bike is that I do not need to be concerned with the battery age on a e-bike. On a e-bike, I can comfortably ride to drain the battery to zero without concern that I might face plant due to weak battery. What I am still not able to get is how battery age affect the safety of a euc. I think when a battery age, its output resistance increase, so just simply measuring the open circuit output voltage will not be able to tell the output resistance. There should be an algorithm in the euc that actually measure the voltage drop versus output current. But it can only do this when the rider is actually riding on the unit which is already too late. Therefore I do not understand how the euc designer avoid the battery aging problem that will affect safety. Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted October 20, 2016 Share Posted October 20, 2016 Laptops seem to be able to sense when a battery is starting to need to be replaced. It must keep track of how quickly it is draining somehow. I don't think EUC control board designers have gotten things quite up to that stage yet, but it's probably a future design element to be implemented. The new Ninebot seems to have some battery cell error detection so I think they are on the right track. Link to comment Share on other sites More sharing options...
hyiu00 Posted October 21, 2016 Author Share Posted October 21, 2016 But knowing how the battery age detection algorithm works will give me confidence in riding. It should not be a proprietary design as every manufacturer should implement it. But I can see a difference from a laptop since a laptop will need to take many seconds to boot into the OS, and the bootup already self test the battery with high power drain. A euc rider will just stand on it as soon as he turns the power on. Link to comment Share on other sites More sharing options...
Chris Westland Posted October 21, 2016 Share Posted October 21, 2016 I think it's the difference between Motors and Motherboards. A computer is going to draw a base of power, and probably is fairly stable in its power usage, consequently it's easy to sense and adjust the current draw. But a motor directly (rubber) linked to the ground with an 80kg (or insert your current weight) downward force demands something approaching infinite torque instantly. I'm guessing that you would get different measurements depending on where you put your probes in the circuit. Any lag in the battery chemistry will show up as a spongy motor response, and this in itself might be hard to measure. I think supercapacitors or flywheels would have a place in EUCs (at least if they were affordable) as they would make small batteries more flexible in driving a motor. But maybe for the added weight, it's just better to get a bigger battery. :-) Attached is a little project (for a gokart) that was done in an MIT summer program. MIT.pdf Link to comment Share on other sites More sharing options...
hyiu00 Posted October 21, 2016 Author Share Posted October 21, 2016 Great paper and I think ultracapacitor is a possible key to improve the safety due to battery aging. The capacitor should have enough juice to get out the "last breath" of energy to safe the rider. This is making the assumption that capacitors are many times more reliable than a battery, if not, there still needs to be a way to test the capacitor capacity and output current capability before and during each ride, which is still a challenge for the euc design. For what we can buy now, seems like the only option is to buy a a euc with bigger battery, do not drain it to below 30%, and sell the euc after one year of usage. So it is still a high cost to maintain. Link to comment Share on other sites More sharing options...
Chris Westland Posted October 21, 2016 Share Posted October 21, 2016 Ultracapacitors are more robust than batteries and you can charge and discharge them a lot more times (and usually need to). Where I think they would help an aging battery is in giving it more time to respond to current surges. This is probably why batteries last so much longer in computers than they do in driving motors; ultracapacitors could help extend their number of charges. Link to comment Share on other sites More sharing options...
HEC Posted October 21, 2016 Share Posted October 21, 2016 For example Inmotion EUCs have battery test as a part of their diagnostic. What exactly is it testing is unknown though. In general it's not that difficult to "measure" battery state as most of the current EUCs already have information about battery voltage and momentary current so with a bit of programming the new firmware should be able to detect aging / deteriorating batteries without need to redesign the controller boards. Link to comment Share on other sites More sharing options...
hyiu00 Posted October 21, 2016 Author Share Posted October 21, 2016 Yes, I believe the battery chemistry can be simulated with respect to aging, and some form of prediction can be done with respect to the instantaneous current, voltage, and temperature behavior of the batteries. But how good is the simulation and the prediction is a mystery. Besides, there are so many brands of batteries that I wonder how good it is for the matching between the controller firmware and the actual battery being used under all environmental conditions. Link to comment Share on other sites More sharing options...
Jurgen Posted October 21, 2016 Share Posted October 21, 2016 The battery in an EUC is a pack of small cell, not a proprietary big battery specifically designed for an EUC. If one cell fails it has an impact on the performance of the whole pack, which happens rather frequently I have the impression. When my Lhotz was "not feeling right" when riding, and I felt it was more easily overtorqued I had the batt checked out, and indeed there were some bad cells in the (Panasonic) pack. The reseller then replaced the cells. So I'm thinking, about about having an annual battery health checkup, same as dentist, intestinal cancer screening, etc Link to comment Share on other sites More sharing options...
hyiu00 Posted October 21, 2016 Author Share Posted October 21, 2016 So the electronics were not sophisticated enough to give a warning of a fail cell. There is still a lot of room for improvement to the electronics and firmware. Ideally this should be a warning from the electronics and not from the rider's "feeling". Link to comment Share on other sites More sharing options...
HEC Posted October 21, 2016 Share Posted October 21, 2016 34 minutes ago, Jurgen said: The battery in an EUC is a pack of small cell, not a proprietary big battery specifically designed for an EUC. If one cell fails it has an impact on the performance of the whole pack, We're talking about two different (though related) issues here: 1. Complete fail of one (or more) individual cell(s) in the battery pack 2. Natural aging of all cells / whole battery pack First scenario will effectively make the battery pack and the whole wheel unsafe and in most cases practically unusable due to the high voltage drop. With the higher S packs (18 or 20S and more) one single faulty cell might still let wheel to work for a while before the cell / pack could be replaced however with 16 - 15 cells or less it's pretty dangerous to continue riding EUC with such bad pack. Second scenario occurs naturally over the time during the lifetime of the whole battery pack / all cells. The maximum capacity the pack / cell can hold decreases, internal resistance increases and maximum current decreases accompanied by higher voltage sag under load. While such battery packs are still safe to use the range will decrease though if the wheel is designed improperly to accommodate this unavoidable change in the battery chemistry it can eventually lead to accident / faceplant if rider will use some more "aggressive" maneuver or encounters some "critical" situation where more power is needed and deteriorated pack can't handle the power demand as when it was new. So yes - the battery check shall be part of your regular "MOT" / checks of your EUC to assure safety of the rider and all surroundings / bystanders. Link to comment Share on other sites More sharing options...
hyiu00 Posted October 21, 2016 Author Share Posted October 21, 2016 15 minutes ago, HEC said: So yes - the battery check shall be part of your regular "MOT" / checks of your EUC to assure safety of the rider and all surroundings / bystanders. So if the euc electronics does not do the test, how to check it for an average rider without the equipment before each ride? Link to comment Share on other sites More sharing options...
HEC Posted October 21, 2016 Share Posted October 21, 2016 4 minutes ago, hyiu00 said: So if the euc electronics does not do the test, how to check it for an average rider without the equipment before each ride? There is not really need to check before every single ride - once a week at best would be sufficient, even fortnight or month would be still pretty safe. Without any (external) equipment whatsoever the only thing you can rely on / use is the EUC's battery lever indicator. It ranges from a single LED (which is green, yellow, red or blinking red - highly insufficient for any detailed battery level monitoring) over the 4 LEDs to multiply LEDs (like 9 on KS-16) all the way to displaying battery level or even precise voltage via mobile app. So all you can do is charge the wheel fully (leaving it for another couple of hours on charger when the RED charging LED turns green to assure all cells are fully balanced) and check the battery level as precisely as possible. Then (while charger is disconnected from the wheel) leave the EUC sit for several hours and check the voltage again, If you see a significant voltage / battery capacity drop you might have one or more faulty cells. If the drop is only slight your pack is probably a bit aged already. It would be much easier to use some (at least basic) tools like digital voltmeter / multimeter, Charge Doctor, watt meter and so on. On some wheels without reverse flow protection on the charging port you can measure the voltage or attach some more advanced battery tester (see below) directly to the charging port of EUC so the above described "test" will be more accurate. If you see significant voltage drop shortly after charging one or more cells are dead for sure. On the EUCs with reverse flow protection on charging port and without detailed voltage / capacity display (either via built in LEDs, display or mobile app) you'd need to gain access to the battery's discharge port and measure the voltage there or install some advanced battery level indicator like this: https://www.aliexpress.com/item/Free-Shipping-12v-Acid-lead-batteries-indicator-Battery-capacity-digital-LED-Tester-voltmeter/32603484431.html The best method though is to use a dedicated battery tester or visit the EUC / E-bike service centre equipped with one to have your battery tested. For this the battery needs to be removed from EUC or at least the cover(s) needs to be removed so it can be disconnected from controller board and access can be gained to both charging and discharging ports of the battery pack(s). tl;dr: It depends on what EUC exactly you have and how detailed is the battery level / voltage display. Link to comment Share on other sites More sharing options...
EU_commuter Posted October 22, 2016 Share Posted October 22, 2016 Indeed. After one and half years of use for my Airwheel X3 (132wh battery), the battery has reach the end of its life. I had a faceplant going up a gentle slop with three leds on. I used the wheel for daily commuting and charged it daily or twice a day some days. Does anyone know how to check the health of battery? I noticed that the charging time got a lot of shorter after a year of heavy use. Link to comment Share on other sites More sharing options...
EUCMania Posted October 22, 2016 Share Posted October 22, 2016 25 minutes ago, EU_commuter said: Indeed. After one and half years of use for my Airwheel X3 (132wh battery), the battery has reach the end of its life. I had a faceplant going up a gentle slop with three leds on. I used the wheel for daily commuting and charged it daily or twice a day some days. Does anyone know how to check the health of battery? I noticed that the charging time got a lot of shorter after a year of heavy use. You need a charge doctor. When the wh drops to below x% ( say 70% ? ) of original, as measured by charge doctor, it is time to change battery. Link to comment Share on other sites More sharing options...
hyiu00 Posted October 22, 2016 Author Share Posted October 22, 2016 4 hours ago, EUCMania said: You need a charge doctor. When the wh drops to below x% ( say 70% ? ) of original, as measured by charge doctor, it is time to change battery. A separate piece of equipment? You have a link? Link to comment Share on other sites More sharing options...
hyiu00 Posted October 22, 2016 Author Share Posted October 22, 2016 7 hours ago, EU_commuter said: Indeed. After one and half years of use for my Airwheel X3 (132wh battery), the battery has reach the end of its life. I had a faceplant going up a gentle slop with three leds on. I used the wheel for daily commuting and charged it daily or twice a day some days. Does anyone know how to check the health of battery? I noticed that the charging time got a lot of shorter after a year of heavy use. The last time I had a cheap hoverboard bought from Taobao, and after one year, I notice that the charging time changed from one hour to about half an hour. I know something is wrong and I immediately sell it in the second hand market. But actually I only used the hoverboard total about 15 hours during the whole year. I think the problem with old batteries are that their output resistances go up, and of course cheap batteries will age faster. Just measuring the voltage with no load cannot tell you the output resistance, and when you draw power from it, the voltage will drop quickly and cannot deliver the power. I am no expert of batteries, but I think somehow the output resistance is related to how quickly the charging voltage reaches the fully charged state. Or simply that when output resistance goes up, the input charging resistance also goes up. Too bad we users have to investigate this ourselves. The euc manufacturers should have this "charger doctor" built into the unit and improve the safety of their products. Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted October 22, 2016 Share Posted October 22, 2016 http://hobby16.neowp.fr/2016/02/06/charge-doctor-v2-10a-3/ Link to comment Share on other sites More sharing options...
hyiu00 Posted November 29, 2016 Author Share Posted November 29, 2016 I just found that there are some battery research from several semiconductor companies. They are all proprietary, but it can give some insight into what is going on in the battery research. Unfortunately they are mainly target towards mobile phones and laptops. Texas Instruments Impedance Track™ Maxim Integrated ModelGauge™ STMicroelectronics OptimGauge™ Link to comment Share on other sites More sharing options...
lizardmech Posted November 29, 2016 Share Posted November 29, 2016 You can build an entire EUC pack with super capacitors now, but it costs about $1200 for a 200wh pack. Still it's not too bad you get 30A continuous charge and discharge, 80A in small bursts, about 10,000 cycles and no fires or chemical hazards. Link to comment Share on other sites More sharing options...
zlymex Posted November 30, 2016 Share Posted November 30, 2016 11 hours ago, lizardmech said: You can build an entire EUC pack with super capacitors now, but it costs about $1200 for a 200wh pack. Still it's not too bad you get 30A continuous charge and discharge, 80A in small bursts, about 10,000 cycles and no fires or chemical hazards. And the size? Link to comment Share on other sites More sharing options...
lizardmech Posted November 30, 2016 Share Posted November 30, 2016 16 minutes ago, zlymex said: And the size? 18 cells of them is 72V charged 45V empty. 111mm x 245mm x 95mm 4kg Link to comment Share on other sites More sharing options...
16bitSprite Posted November 30, 2016 Share Posted November 30, 2016 On 23/10/2016 at 4:30 AM, Hunka Hunka Burning Love said: http://hobby16.neowp.fr/2016/02/06/charge-doctor-v2-10a-3/ Thanks for the link. I had several cut outs due to poor battery health on my old wheel. Not such a problem when traveling under 12kph. I don't want to find out what its like when a cutout happens at 30kmh. Just ordered mine. Possible life saver here ^ Link to comment Share on other sites More sharing options...
Chris Westland Posted November 30, 2016 Share Posted November 30, 2016 On 10/21/2016 at 1:43 AM, HEC said: For example Inmotion EUCs have battery test as a part of their diagnostic. What exactly is it testing is unknown though. In general it's not that difficult to "measure" battery state as most of the current EUCs already have information about battery voltage and momentary current so with a bit of programming the new firmware should be able to detect aging / deteriorating batteries without need to redesign the controller boards. My guess would be that all of the EUC mfrs are using off-the shelf chips to perform these functions. So battery measurements would be done by something like Maxim Integrated's "Battery Fuel Gauge" chip, which would give you a pre-determined suite of metrics. Link to comment Share on other sites More sharing options...
Chris Westland Posted December 1, 2016 Share Posted December 1, 2016 The relevant Maxim chips use the FuelPack (Pack) algorithm which is detailed in the attached PDF. The Maxim chip which fits the bill for these 16 cell EUCs is MAX14921 which costs ~$6 in quantity. I'm presuming this is what is used in my IPS Zero. MAX14921 High Accuracy 16 Cell Measurement AFE Status Monitor 3-16 Cell Li-Ion SPI - Temperature Voltage - Pack Over-Temperature Over/Under Voltage 6 65 AFE Daisy Chain Bus External MOSFET Drivers Protection Circuitry Simultaneous Sampling - TQFP/80 -40 to +85 $6.16 @1k AN2412.pdf Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.