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esaj

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Posts posted by esaj


  1. 21 minutes ago, mrelwood said:

    The power ratings must be taken with a huge grain of salt, for every manufacturer. Announcing the inherently varying amount of power with just a single number is just not precise enough. So a 2200W wheel is not at all necessarily more powerful than a 2000W wheel.

    Don't know for sure, but I think the nominal numbers are more like "this is the average power the motor manufacturer has calculated that the motor should withstand in normal conditions constantly (like infinitely) without burning", and even then they're of course highly likely rounded. I'd imagine a western manufacturer would downplay the numbers and use conservative values so that customers couldn't claim warranty for cases where the motor was burned by overpowering it constantly, but for other (read: Chinese) manufacturers, it might be "better" to overestimate it.

    Nevertheless, the peak powers during extreme situations can be multiples of these, whereas riding on a flat surface at a steady speed requires very little power (a few hundred watts, or roll down even slightly declining road, and you could see close to 0W, or slightly negative power when the motor is actually braking a little to keep you balanced). Most of the time you aren't really using that much power. More likely the batteries will be the limiting factor, rather than whether the motor can take it. I'd assume it'd take a good while before the motor actually got damaged (read: overheat, melt the lacquering around the coils and short circuit it, at least I can't think of another way to destroy this kind of motor with plain current, not voltage) through overpowering, people have done long hill climbing tests and such, and if something blows, it's usually the mainboard MOSFETs, long before the motor. Or overleaning and ending up on their face, but with the amount of power the current wheels have, I'd think you'd really have to try that on purpose and hard, and going fast enough to overcome the battery voltage is a whole another issue (who's crazy enough to try that with these speeds)...

    The difference between 2000 and 2200W, in my opinion, is just marketing ;) 


  2. I have a Firewheel F260, in pieces, in the room next to me right now... It's a funny piece of the EUC history, but I don't see much point in reviving it, unless you have the parts handy (there were mainboards floating around at least two-three years back, I think, but finding one now might be iffy). Compared to pretty much any "modern" (released within a couple of years) wheel, the wheel itself is not that good, while not really bad either (for its own era, that is  ;))

     

    The video's uploaded in 2014. Looks a bit flaky these days, it can barely climb the hill with the low weight rider ;) 

    The mainboards had several revision that had more or less flaky lifetime, although some would just keep on working seemingly "forever" (well, at least a couple of years, don't know if @dmethvin still rides his? :P), or not, mine blew up a couple, although at least one case was probably my own fault, trying to get longer range with custom batteries, the board shorted after assembly on power up...

    The motor's nominal power is 550W (that's not a typo, it's actually 550W, not 500W, we hunted the motor specs back in the day :D), of course much higher in spikes, but modern wheels sport 1000-2000W nominal values, much higher in spikes.

    The 260Wh battery (actually 264Wh) of F260 is miniscule by todays standards, even the largest battery-model "F799"  (it was something like 16S4P with 776Wh) isn't that big these days. Even if you don't need the range, more cell-series in parallel (the "P"-number in the battery configuration) means that there's less resistance, so more packs can dish out more current for the motor when it's needed (read: more power, torque!). The battery can't provide nowhere near as much power as the modern wheels. I'm still riding a 3 year-old KS16S, and it's already "next level" compared to the Firewheel, although it's still in the same "battery league".... But I did take the F260 slightly above 30km/h regularly (and basically risked breaking my neck all that time, heavier rider would likely have faceplanted multiple times, I weigh <60kg/130lbs). This was the time when things like "battery shunting" (bypassing the battery discharge protections) was still common, just to prevent the battery protections from causing faceplants, because we went over the limits by so much! :D A "slight" possible complication with the practice was that if the batteries were short-circuited (like by a shorted mainboard), they could catch fire...


  3. 1 hour ago, Zulix said:

    I think the chances I won't like it are slim to none, really. It looks so fun. But since I've no way to try one, I have to admit it's possible.

    It is possible, at least @Jason McNeil has mentioned that he has had one return in the past, where the buyer told him that he just couldn't learn it, after a long time of trying. But, I'd claim that vast majority of people who stick with it will learn it eventually, and enjoy it (although to be fair, those who don't likely won't come to the forums to tell that, but still I'd say pretty much any person in the world capable of riding a bicycle will learn it if they really want to). The initial learning before things "click" varies wildly, from days to months before being ready to ride in the "general public", of course the only judge of that is the rider him/herself, as there's no license or such required anywhere as far as I know. Just getting going without any support might take a while (I didn't have anything to lean on when starting on the street, don't know if that made things quicker or not... I had to jump on and off the wheel for a good 30 minutes or so, sweating like a pig, before I could get even my first couple of feet with both of my feet on the pedals...). Some people with "manual" unicycle -experience might pick it up in minutes. ;)  Apart from the learning curve, I find it highly unlikely someone who does all the "work" of learning about the wheels themselves before getting one wouldn't like it. Who'd even spend all that time trying to learn (+ money to buy) and then realize it's not something they actually wanted? But, I guess (I don't remember anymore, and was "lucky" to learn fairly quick) the learning curve in the beginning can be depressing if you feel you're not progressing (but even that's likely temporary, a week later from feeling like you're not "getting" it or progressing, you' could be riding without issue).

    There's a huge amount of information, tutorials, reviews, general chatter, moral support etc. etc. in these forums, so much that I've actually more or less given up trying to stay on top of things a few years back... :rolleyes:  Look around, you'll learn things the videos never show or tell you  :P  And most of all, welcome to the forums and enjoy, it's going to be heck of a ride  ;) 

     


  4. On 4/22/2020 at 12:05 AM, FunkyWheeling said:

    Tää on kyl jotain jäätävää. Ei mee kauaa kun 100km/h rikotaan tällä menolla.

    Jos joku alkaa hommata tällasia oikeesti,  niin pitäkää kuitenkin pliis järki päässä. Suomen kokosessa maassa kun joku kiskasee "sata lasissa" jonkun päälle, niin sit onkin ihan

    BUnDS37CYAAw2ce.jpg

    ;) 


  5. I doubt it would be the battery packs themselves, the side-leds show that the voltage measured by the mainboard fluctuates a lot when the charge port is touched. I'd put my money on mainboard or something weird going on with contacts. Since it disappears for some time after dismantling the wheel and putting it back together it could be contacts... Or some weird static build-up issue?

    As I recall, the charge port in KS16S goes straight to the mainboard, then separate wires go to each battery pack?


  6. On 11/3/2019 at 7:36 PM, Flying W said:

    When my batter at the connector shows 83.7 wheelog shows 82.6v. Oddly my original board would show 83.4 when full on wheelog. Changes boards at 340 miles and wheelog has showed 82 and change ever since (for the last 2300 miles) so I'm guessing the boards report with differing amounts error to wheelog. 

    I think it was @DaveThomasPilot who pointed out a (common?) design mistake in the reverse engineered Firewheel mainboard in how the wheels measure the battery voltage (probably common in many wheels): the usual set up is using very high resistances (hundreds of kilo-ohms) to form a voltage divider (you can't exatly put up to 84V direcly to an analog converter-pin in a 3.3V microcontroller without magic smoke coming out of everywhere ;)), and then a small-valued multi-layer ceramic capacitor (MLCC) paralleled with the low-side resistor to filter the fluctuations:

    BVxZzAl.png

    The issue is that the MLCC will have a (very small, like micro-amperes, µA) current leak, but with large resistances this current leak becomes more significant vs. how much current the large-valued high-side resistor "allows" to flow, skewing the measurement lower. Furthermore, the resistors are just "plain" 1% tolerance, with 84V +-1% is already +-0.84V (not to mention if they're at the "far ends" of their tolerance error, ie. one is +1% while the other is -1%, although this is very, very unlikely, and probably the +- percentage error of the resistors themselves is smaller than 1%). But then again, that's not the only error source in the measurement, so the total error can be higher.

    TLDR; the measurements done by the wheel itself using the divider in the mainboard may have 1% (or even more) of error in them, usually towards lower than the real voltage. Shouldn't be really much of an issue outside the owner being confused why the voltages seem slightly out of whack; If you measure your charger putting out the "correct" voltage with a fairly accurate multimeter and there are no issues with charging or riding, everything's highly likely just fine.


  7. On 5/2/2020 at 9:20 AM, mrelwood said:

     

    I have read about several cases where the battery had developed a severe misbalance seemingly because the user always unplugged the charger as soon as the light turned green. I don’t have any actual first hand knowledge on wether the balancing process happens mostly at the beginning or at the end of the CV charging, but it does seem that leaving the charger plugged in even after it turns green could a good idea for the longevity of the pack.

     

    On 5/2/2020 at 10:56 AM, Planemo said:

    And thats how I have always thought of it too, but I assumed that at some point the charger would shut down totally (once peak voltage had been met and no more than say 300mA was being drawn) but if that isnt the case then how long after the green light comes on is too long? Sounds like a bit of a lottery if you want to carry out a full balance charge but not harm the pack.

    Pretty poor show really. Luckily I have never left my wheels plugged in for any considerable time (I think max is about 3 hours) after the green light but I bet a lot of people do (overnight charges for instance).

    Or, are we saying that the big packs we are generally using can tolerate being fed 300mA for such lengthy periods that theres no need to build in a total shut off circuit?

     

    Well, I have no real answers, but just for a single reference:

    I have had my KS16S / 840Wh (16S4P with Sanyo cells, don't know the exact model though) for over three years now (manufacturing date for the wheel itself is 17.03.2017 based on serial number, of course the batteries are made before that). I'd love to tell the mileage, but for some reason the non-music BT is very, very touch'n'go (usually no-go, like right now) with my current phone. I'm still using the old "green app". The firmware is still 1.00, never updated. :P Not ridden very much, I'd guess less than 5000km / 3000 miles, but could be wrong. The usage pattern has been:

    -mostly commuting (depending on where I worked each year, this could be 10 to 25km per weekday) and some errands for 5 days a week on average, between late April/early May and late September / early October (about 5 months per year)

    -Occasional "fun rides" here and there, 10-50km at a time, but not very often

    -Stored in room temp totally unused at 30-40% charge for rest of the year (about 7 months per year)

    I don't remember the last time I checked the total capacity (might be a couple years), but at that time it was still at around the nominal 828Wh or slightly above (the 840Wh -number is calculated with rounded values, but every manufacturer does that, and on the few occasions I've had the chance to measure new cells, they've been above the nominal mAh -rating, for brand-cells that is).

    I usually charge all the way to full on weekday evenings (when I know I'll ride it to work in the morning), that is, usually something like 10-70mA charge current at full voltage (measured with Charge Doctor V2) when the charging is stopped. Disconnect before I go to bed, most of the time it has easily reached <100mA charge current at that point, I'd guess usually something like 0.02-0.04A (20-40mA). The wheel is then left as is in room temperature until next morning. Against weekend, I don't charge the wheel on Friday-evening, unless I know I'm going riding on Saturday morning, usually I just charge "as needed" on weekends, and do a full charge on Sunday evening.

    Since I have the Charge Doctor, I don't pay any real attention to the charger light, but the charger I use goes to green around 250mA. I have forgotten to unplug and left the wheel being charged overnight now and then, but not often... less than 5 times per year, I'd say, more like 1-2 probably on average.

    No dead cells, no indication of any abnormal wear & tear on cells. I can still do the stupid "from zero to full speed so fast that the tiltback scares the shit out of you" -accelerations without issue. Of course, now that I say it, it might fail on me the next time... knock on wood.  ;) And I'm lower weight than your average rider (about 60kg / 130lbs). But for all I can tell just by riding (haven't bothered to tear it down for accurate measurements), this usage pattern hasn't at least significantly hastened the doom of the cells. 

    I'll try to do a full "ride it all the way to dry" -test some day and measure the total capacity of the cells. Likely they have degraded, since the cells probably lose at least a couple of percent of total capacity each year even when stored "perfectly". Let's hope I'm not in for a nasty surprise, but it's fairly likely that I couldn't break 60km/37 miles on these cells anymore....


  8. On 4/23/2020 at 6:25 AM, /Dev/Null said:

    Here is a Brazilian reseller.  I know they are in my "Electric wheel Portuguese" group in FB.

    Not sure if they are here on the forums...

    https://loja.eletricz.com.br/

    Found them when my niece mentioned she'd love to learn to ride.

    They carry KS & Gotway

    https://loja.eletricz.com.br/veiculos/monociclo-eletrico

    Edit @esaj, can we get this store added to the top post?  I should have tagged you earlier...

    Sorry for the delay, I don't visit the forums that often anymore or check the threads... quickest way to get my attention is tagging or sending a private message, but the delay might still be (up to) several days. Usually when I visit I may have tens or hundreds of notifications of posts requiring approvals and such, so even tags might get lost in the mass.


  9. I haven't actually followed the local domestic news that much for the last few days. Part of the country was isolated, and people can get fined if they try to cross in or out of the "zone" without a good reason (work usually), but other than that, there's no actual curfew declared or such, just a request for people to socially distance themselves, work remotely if possible, avoid visiting stores often etc, and AFAIK, it's going fairly good, people are doing that. Restaurants are allowed only to sell take out and most other such "gathering places" are shutdown.

    I haven't been outside except for a smoke and taking out the dog for almost three weeks :P  My spouse handles the groceries, she goes to the store once or twice a week. I "evacuated" my work stuff from the office on Tuesday 17th of March, and immediately afterwards fell ill for the rest of the week. Don't know if it was just seasonal flu or Covid-19 or something else, pretty mild symptoms, fatique and low fever mostly. Still not 100%, but definitely not dying or in need of medical care.

     


  10. 12 hours ago, Toshio Uemura said:

    This is not latest news, but I think it is still interesting to know:

    Excerpt from the South China Morning Post:

     

     

    610C5905-E185-4056-AB36-88E92D68E5D0.jpeg
     

    This would also explain to me the “stealth like” spread of this “intelligent” virus. I am well aware that viruses are neither alive nor intelligent, but so is AI. 😝 

    So: is it man made or zoonotic after all. (THAT is not a suggestion, just a question I would love to hear opinions and possibly more data to.)

    https://en.m.wikipedia.org/wiki/Misinformation_related_to_the_2019–20_coronavirus_pandemic

    Never read the entire thing through, and probably the information has changed since, but at least earlier there were many conspiracy theories with countries blaming each other of creating the virus, yet all the experts studying the virus said that it is naturally evolved...

     


  11. 2 minutes ago, Toshio Uemura said:

    Ibuprofen is used for keeping down the body temperature 🤒 Aspirin and other similar medicaments are widely used in Italy to treat CoViD-19 patients there. Some sources suggest that this may be the reason for the high mortality in Italy. It is the highest in Europe.

    So. Suppressing the fever might not be a good idea at all.

    I am not a doctor, but I myself would try to ride it out naturally without lowering the body temperature by using drugs like Aspirin or Ibuprofen. 

    Mixed up the names ( edited it to "Should I be eating Burana (tradename for ibuprofen) as a precaution?", shows how much I know about medicine :D), but anyway, the point was that people are eating painkillers before they even know if they're sick.

    Usually when I have the flu, I just drink water and take some vitamins.


  12. 7 minutes ago, Toshio Uemura said:

    Many people have trouble to deal with this situation.

    No shit? ;) People are panic buying all the toilet paper, non-perishable food, painkillers, vitamins and nutritional supplements. My sister works at a hospital pharmacy and knows other pharmacists working at "normal" pharmacies. People are asking things like "Should I be eating Burana (tradename for ibuprofen) as a precaution?". I don't know anything about chemistry or medicines really, but even to me that sounds pretty stupid...


  13. Just now, Roland said:

    In other news:
    Merkel has brought down the quarantine hammer. 
    Germany is basicly shutdown.  

    Yeah, EU is also planning on closing Schengen-area borders on Wednesday or Thursday and most countries have limited or stopped air travel completely. Apparently also in many countries anyone returning from another country is placed in a 2 week quarantine as a precaution.


  14. https://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures

     

    Quote

    The performance of all batteries drops drastically at low temperatures; however, the elevated internal resistance will cause some warming effect by efficiency loss caused by voltage drop when applying a load current. At –20°C (–4°F) most batteries are at about 50 percent performance level. ... Specialty Li-ion can operate to a temperature of –40°C but only at a reduced discharge rate; charging at this temperature is out of the question.

    Figure 1 illustrates the discharge voltage of an 18650 Li-ion under various temperatures. A 3A discharge of a 2.8Ah cell represents a C-rate of 1.07C. The reduced capacity at low temperature only applies while the cell is in that condition and will recover in room temperature.
     

    Discharge Voltage by Temperature
    Figure 1: Discharge voltage of an 18650 Li-ion cell at 3A and various temperatures.
    Cell type: Panasonic NRC18650PD, 2.8Ah nominal, LiNiCoAlO2 (NCA)
    Source: Technische Universität München (TUM)


    Matched cells with identical capacities play an important role when discharging at low temperature and under heavy load. Since the cells in a battery pack can never be perfectly matched, a negative voltage potential can occur across a weaker cell in a multi-cell pack if the discharge is allowed to continue beyond a safe cut-off point. Known as cell reversal, the weak cell gets stressed to the point of developing a permanent electrical short. The larger the cell-count, the greater is the likelihood of cell-reversal under load. Over-discharge at a low temperature and heavy load is a large contributor to battery failure of cordless power tools
    (See BU-803a: Cell Matching and Balancing.)

    The driving range of an electric vehicle between charges is calculated at ambient temperature. EV drivers are being made aware that frigid temperature reduces the available mileage. This loss is not only caused by heating the cabin electrically but by the inherent slowing of the battery’s electrochemical reaction, which reduces the capacity while cold.

     


  15. 16 minutes ago, z3n said:

    Models

    At present, we have designed 3 models of the Satiator charger optimized for different voltage ranges all sharing the same great feature set and firmware. The 48V 8A and 72V 5A models are both in full production, while the 24V 15A model is available for samples from interested OEM parties.

    Model Name 2415 4808 7205
    Max Voltage 36V 63V 103V
    Max Current 15A* 8A* 5A*
    Typical Batteries 12-24V 24V-52V 36V-84V

    *Current also clamped by 360 watt power limit

    Thanks for the heads up, so it needs to be the 7205 to charge the KS 16X (20S = 84V battery pack). Edited my post above.

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