Citi Wheel Posted November 28, 2015 Share Posted November 28, 2015 https://youtu.be/28arkgLua-o Tested the limits of the motor on the msuper HS. Looks like max the motor can output is around 4900 watts and 85 amps. It was actually pretty tough to over lean it, with the powerful motor. When it fell in the video below, I rocked it back then forward, and it gave. Link to comment Share on other sites More sharing options...
SirGeraint Posted November 29, 2015 Share Posted November 29, 2015 You should enable recordings so you can see all of the readings. I've seen -5245W (-85.34Amps) while stopping without a cutout. I wasn't rocking back & forth. Link to comment Share on other sites More sharing options...
zlymex Posted November 29, 2015 Share Posted November 29, 2015 According to my tests by using a precision current shunt, the current(Amp) reading by Gotway is over exaggerated by a factor of 2.2. That is, when Gotway gives 22A, it actually 10A. More over, the power from the app is the voltage times the current, I assume it's the board input power, not the input power of the motor, much less the shaft power of the motor. The rated motor power is the shaft power(mechanical) by definition here in China. Battery output power(A) > Board input power(B) > Board output power(C) > Motor input power(D) > Motor output power(E). Board Efficiency = C/B*100% Motor Efficiency = E/D*100% Board Efficiency(F) become low at large current. Motor Efficiency(G) become low at low speed. By my uphill tests of MSuper2 MS, F*G = 60% max. Link to comment Share on other sites More sharing options...
esaj Posted November 29, 2015 Share Posted November 29, 2015 I could and probably should add adjustable correction factors in the app for both speed & current, which seem to be exaggerated by the mainboard... the app pretty much just shows the values the wheel mainboard sends to it. Link to comment Share on other sites More sharing options...
SirGeraint Posted November 29, 2015 Share Posted November 29, 2015 Thanks for that information @zlymex. I can see where a manufacturer would want to exaggerate the speed but I am surprised that they would feel the need to exaggerate the current. Could it be that they made a rough approximation? Or a bad calculation? But at least we are comparing apples to apples (or exaggerated apples to exaggerated apples). So, do you know which measurement(s) is/are used to determine when to cut-off? Is there an absolute limit that we could go by? Link to comment Share on other sites More sharing options...
zlymex Posted November 30, 2015 Share Posted November 30, 2015 On 2015/11/30 at 3:45 AM, SirGeraint said: Thanks for that information @zlymex. I can see where a manufacturer would want to exaggerate the speed but I am surprised that they would feel the need to exaggerate the current. Could it be that they made a rough approximation? Or a bad calculation? But at least we are comparing apples to apples (or exaggerated apples to exaggerated apples). So, do you know which measurement(s) is/are used to determine when to cut-off? Is there an absolute limit that we could go by? When I bought my first EUC(IPS 122) last year, I soon made current(Amps) tests by inserting a LEM current sensor at the battery output wire and made recording, charting etc, got some ideas of what the current and power of the EUC at various circumstances. I opened the metal box inside and found two current sensor ICs(ACS709LLFTR-35BB) connected to two of the three motor output wires. However, I found no other current sensor to read the total current drawing from the battery. On later IPS models such as Lhotz, there is no current reading on the app screen. Then I bought my second EUC which is Gotway mcm2 with blue tooth, I immediately noticed the unusual high current readings from the app. I thought something wrong with the EUC so I informed one of the a/s in Gotway but he insisted that it is quite normal. Since the EUC performed good and the mileage range was Ok and also no body care about the current, I had no further complaint. The app at that time is not very friendly especially when reading current, every other reading such as voltage and temperature is halted. I asked one of my friend to make an app mainly for recording(as .csv files). He also had difficulty in sampling the current and the voltage at the same time. I had to make two runs to record current and voltage separately. I opened the case of the EUC as well and found no current sensor either. I still don't understand how Gotway got the current. When I bought my MSuper2 this year, the main board is different than mcm2, there are two current sensor ICs(same as IPS) connected in the same way as IPS. I don't think these are the current sensors used for current reading because they may use the same sensorless method as before. I don't think they exaggerate the current on purpose, it might because of the way the current is sampled or calculated. From my lab experience, it must be very difficult to measure the current precisely without a proper current sensor. This can be easily demonstrated by the following example. Step one foot on my MSuper2 and make it lean back but without moving, I can managed to get a constant current reading of over -20A without much effort. How could that be possible? Negative current means charge to the battery! I made no work(work equals force times distance) to the EUC let alone charge the battery at more than 1000 Watts of power(20V*65V=1300W). Later I use a DC clamp meter to measure the actual current and it says 1.24 Amps(the sign is plus meaning drawing current from the battery). This shows the extreme unreliable of the current reading by Gotway at standstill, how can you believe the current reading to be correct when moving? (even if the sign is wrong, 21.1A vs 1.24A, what a difference) Link to comment Share on other sites More sharing options...
esaj Posted November 30, 2015 Share Posted November 30, 2015 43 minutes ago, zlymex said: I asked one of my friend to make an app mainly for recording(as .csv files). He also had difficulty in sampling the current and the voltage at the same time. I had to make two runs to record current and voltage separately. I opened the case of the EUC as well and found no current sensor either. I still don't understand how Gotway got the current. Hobby16 made a comparison of 14" King Song vs. 14" Gotway (MCM2s maybe?) mainboards, it shows the current sensors on Gotway board (but maybe yours was the older model?) http://hobby16.neowp.fr/2015/07/29/king-song-gotway-comparison/ Quote Step one foot on my MSuper2 and make it lean back but without moving, I can managed to get a constant current reading of over -20A without much effort. How could that be possible? Negative current means charge to the battery! I made no work(work equals force times distance) to the EUC let alone charge the battery at more than 1000 Watts of power(20V*65V=1300W). Later I use a DC clamp meter to measure the actual current and it says 1.24 Amps(the sign is plus meaning drawing current from the battery). This shows the extreme unreliable of the current reading by Gotway at standstill, how can you believe the current reading to be correct when moving? (even if the sign is wrong, 21.1A vs 1.24A, what a difference) This is all theoretical (and I'm not that good with electronics), but from testing with Vee's MCM2s, I know that the sign of the current changes according to the direction the motor is turning (it shows positive values for one direction and negative for the other), so my guess is that it also measures the direction of the current (if the current would be measured as a voltage drop over a shunt resistor, couldn't the direction be inferred from the voltage drop polarity?). Although I guess it's possible that they just send it as negative or positive value based on simply the direction the motor is running... Also, could it be possible that if the current is measured from the motor phases, the current could actually be higher at the motor phase than from the battery because the voltage at the motor phase is lower (for roughly the same power, P = UI, so if U is lower, I must be higher)? Just speculating really... Link to comment Share on other sites More sharing options...
Chriull Posted November 30, 2015 Share Posted November 30, 2015 7 minutes ago, esaj said: This is all theoretical (and I'm not that good with electronics), but from testing with Vee's MCM2s, I know that the sign of the current changes according to the direction the motor is turning (it shows positive values for one direction and negative for the other), so my guess is that it also measures the direction of the current. Also, could it be possible that if the current is measured from the motor phases, the current could actually be higher at the motor phase than from the battery because the voltage at the motor phase is lower (for roughly the same power, P = UI, so if U is lower, I must be higher)? Just speculating really... Changing the sign according to the direction the motor is turning is bullshit The direction of the wheel is determined by the sequence one put current on the different motor coils and not by the direction of the current. The current is in either direction the wheel turns, from the battery to the motor. Link to comment Share on other sites More sharing options...
zlymex Posted November 30, 2015 Share Posted November 30, 2015 11 minutes ago, esaj said: Hobby16 made a comparison of 14" King Song vs. 14" Gotway (MCM2s maybe?) mainboards, it shows the current sensors on Gotway board (but maybe yours was the older model?) http://hobby16.neowp.fr/2015/07/29/king-song-gotway-comparison/ Yes, there are two current sensor ICs on the Gotway's pic, same as I described on my MSuper2. But I don't think it is the current sensor used for current reading by the app. 24 minutes ago, esaj said: This is all theoretical (and I'm not that good with electronics), but from testing with Vee's MCM2s, I know that the sign of the current changes according to the direction the motor is turning (it shows positive values for one direction and negative for the other), so my guess is that it also measures the direction of the current (if the current would be measured as a voltage drop over a shunt resistor, couldn't the direction be inferred from the voltage drop polarity?). Although I guess it's possible that they just send it as negative or positive value based on simply the direction the motor is running... Also, could it be possible that if the current is measured from the motor phases, the current could actually be higher at the motor phase than from the battery because the voltage at the motor phase is lower (for roughly the same power, P = UI, so if U is lower, I must be higher)? Just speculating really... I think Gotway was wrong putting a minus sign on the current when the motor's direction is reversed. As I've mentioned early, even if the sign is plus, 21.1A is still much higher than the actual current of 1.24 Amps. Different measurement point make different results especially the current at the motor phase output is PWM modulated. However, the question becomes whether the current measurements is linear and the line is through the original point. Link to comment Share on other sites More sharing options...
esaj Posted November 30, 2015 Share Posted November 30, 2015 14 minutes ago, Chriull said: Changing the sign according to the direction the motor is turning is bullshit The direction of the wheel is determined by the sequence one put current on the different motor coils and not by the direction of the current. The current is in either direction the wheel turns, from the battery to the motor. Like I said in my edited answer just before you posted, it could be that they just change the sign programmatically in the data sent based on which direction the motor is running... As for the direction of the current, I actually began to wonder if this would work: I'm not saying this is how it's measured in any wheel, but just as an idea, I'm not 100% sure if it actually even works like that If the current were to be measured from the phase of the motor in between the half-bridge mosfets, the voltage drop sensed over a very small resistor would have larger potential in different side depending which direction the current is running in said phase. If mosfets 1 and 6 are conduction (like in the upper image), the voltage drop over the resistor in phase a would occur "towards the motor", and if mosfets 3 and 2 are conducting, the current traverses in opposite direction over the resistor (and if you want to be really pedantic about it, the electrons go in the opposite direction than what I've drawn here ). Although inductive kick backs and the "noise" of pwm-driven mosfets would probably make it really hard to get any sensible readings, but could that work in principle? Now I'm super pissed that the postal service strike f***ed up my delivery schedules, I have 50+ packets coming in from China with all sorts of parts (motors, microcontrollers, sensors, breadboards, prototype PCBs, basic electronics components etc. etc.) to test stuff like this, but have been waiting for about three weeks now, and they're saying the deliveries might get back to schedule maybe next week... Link to comment Share on other sites More sharing options...
SirGeraint Posted November 30, 2015 Share Posted November 30, 2015 2 hours ago, zlymex said: Step one foot on my MSuper2 and make it lean back but without moving, I can managed to get a constant current reading of over -20A without much effort. How could that be possible? Negative current means charge to the battery! I made no work(work equals force times distance) to the EUC let alone charge the battery at more than 1000 Watts of power(20V*65V=1300W). Later I use a DC clamp meter to measure the actual current and it says 1.24 Amps(the sign is plus meaning drawing current from the battery). This shows the extreme unreliable of the current reading by Gotway at standstill, how can you believe the current reading to be correct when moving? (even if the sign is wrong, 21.1A vs 1.24A, what a difference) Yes, I noticed that too. Just moving the MSuper2 back and forth by hand shows positive & negative currents. With the Ninebot One E+ when you get a negative current it is really regenerative. I figured it must've been different due to where they were sampling the current. Link to comment Share on other sites More sharing options...
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