2WD (Two-Wheel Drive) FAQ

[Hangdog98]

My front motor is a 180rpv Keyde and my rear is a 160rpv. I specced these by guesswork thinking that I'll want the front to have less torque travelling at the same speed as the rear because it has less traction available. The keyde has 5 different amp settings and I run the front one-click less than the rear and that seems to provide good assistance and less front wheel spin. I'm trialling the bike on a more challenging track this weekend so I sould have more data to share afterwards

 

[motomech]

Hello, I am a user of a 2WD e-bike. It's powered by 2 x Q100 36V/201rpm and 2 x 36v/14A controllers. It is perfect for my region, the Alpes. But I would like a bike equipped for much more speed, still with uphill ability. So I was thinking of 2 x Q100 24v/328rpm and 2 x 36V/23A controllers. I have simulated this configuration on the ebike.ca simulator and it looks perfectly OK: max speed 53 km/hr, no overheat up to 7.5% grade.
Has anyone tried this configuration? Or do you have any concern with it?
Thanks.

My results on the sim. are quite different. 2) 328's @ 36V gives a top speed of 40 Kph, and that might be a little high.
That combination is not ideal. Note that nether motor gets into it's more efficient RPM zone. The controllers will want a lot of Amps, hurting range
1) 328, 26" wheel, Alps would deffinately would be a bad idea, both two motors would certainly help, as you can split the power.
A 48V Battery with the 201's would be a better option. The top speed would be the same as the 36V 328 combo., but it would climb better.
Those are high power controllers you are suggesting. Perhaps @ 36V they would be OK, sort of depends on the controller(some hit harder than others).
My bike is: Frt. 328 in 24" wheel, 11S Lipo(44V) w\ a 24 Amp controller. Rear 328 in 24" wheel, 12S(47V) w\ 17 Amp controller.
The frt is a little too much, the motor makes noises of objection, but it is flat here and I only use the frt. motor for short bursts of acelleration.
The rear is smooth and great for assist. Single motor top speed is 36 Kph, both is 40 Kph.
I very much like the 9-FET controllers from Elifebike. Inexspensive, smooth, quiet and they have a very good LVC for 48V.(42V LVC).

 

[d8veh]

Hello, I am a user of a 2WD e-bike. It's powered by 2 x Q100 36V/201rpm and 2 x 36v/14A controllers. It is perfect for my region, the Alpes. But I would like a bike equipped for much more speed, still with uphill ability. So I was thinking of 2 x Q100 24v/328rpm and 2 x 36V/23A controllers. I have simulated this configuration on the ebike.ca simulator and it looks perfectly OK: max speed 53 km/hr, no overheat up to 7.5% grade.
Has anyone tried this configuration? Or do you have any concern with it?
Thanks.

That won't work at all. They'll melt.

If you already have a pair of the standard 201 rpm Q100s, you can change them to Q100Hs, which will increase your speed from 25km/h to 32 km/h. A pair of 328 rpm ones will give 40km/h, but your 14A controllers will overheat unless you can keep the speed above 25km/h most of the time. A pair of 36v Q100Hs at 48v and two 20A controllers should go pretty well, but you need a very high discharge battery to provide those 40A, so it'll probably be quite big an heavy. Make sure that you plan the battery first because you need somewhere to install it, which is probably the most difficult thing. Schwibsi might be able to make you a custom battery if you need something like that.

Another option would be to keep your present motor and increase the battery voltage. 36v controllers can go to 44v (12S lipos) for a 20% speed and power increase. Go up to 48v for a 30% increase, but you'll need two new controllers at about 15A, which are not so common, though they are available.

 

[sange]

Motomech, d8veh, Hangdog98 ,

Thanks for your feedbacks.
I am planning to use existing batteries. I have two 36V/10Ah batteries. So the choise of the batterie is already done.
I will rprobably use the same motor on for the front and back, although I know that the rear wheel can get a better grip. The idea is to overvolt a 24V motor. And since it is a 2WD, there will be enough power to target for a 50 km/hr maximum speed. But the intend is not to cruise at the max speed all the time but only when road conditions allow it. Then the motors will run close to their maximum efficiency, i.e. with very low heat generation. I will probably use a LCD3 display to adapt current and speed to the road conditions, e.g. a 30km/hr max speed in urban areas, current down for steep hill,...
To set the ebike.ca simulator I have used the Q100 328rpm motor, with a.55.5V battery (to simulate the 24V motor version : 24V*37v/24v) and 15.3A controller (also to simulate the the 24V motor : 23A*37v/24v), and the bike loads are divided by 2 (‘custom frame’ and ‘custom weight’). That set gives a 53 km/hr max speed and a 8% road grade without overheating which is perfect for my usage.
I see two issues with this set up. The motor gearing might not be happy with the 23A controller, and a wrong set up of the lcd3 vs the road conditions might burn the motor, e.g. keep the maximum current in a >10% hilly road.
Now I could simply move to 36V/328rpm motors and a 14A controller to avoid these potential issues.
Are my reasoning and conclusion right ?
Thanks.

 

[motomech]

Motomech, d8veh, Hangdog98 ,

Thanks for your feedbacks.
I am planning to use existing batteries. I have two 36V/10Ah batteries. So the choise of the batterie is already done.
I will rprobably use the same motor on for the front and back, although I know that the rear wheel can get a better grip. The idea is to overvolt a 24V motor. And since it is a 2WD, there will be enough power to target for a 50 km/hr maximum speed. But the intend is not to cruise at the max speed all the time but only when road conditions allow it. Then the motors will run close to their maximum efficiency, i.e. with very low heat generation. I will probably use a LCD3 display to adapt current and speed to the road conditions, e.g. a 30km/hr max speed in urban areas, current down for steep hill,...
To set the ebike.ca simulator I have used the Q100 328rpm motor, with a.55.5V battery (to simulate the 24V motor version : 24V*37v/24v) and 15.3A controller (also to simulate the the 24V motor : 23A*37v/24v), and the bike loads are divided by 2 (‘custom frame’ and ‘custom weight’). That set gives a 53 km/hr max speed and a 8% road grade without overheating which is perfect for my usage.
I see two issues with this set up. The motor gearing might not be happy with the 23A controller, and a wrong set up of the lcd3 vs the road conditions might burn the motor, e.g. keep the maximum current in a >10% hilly road.
Now I could simply move to 36V/328rpm motors and a 14A controller to avoid these potential issues.
Are my reasoning and conclusion right ?
Thanks.

I am pretty sure the 24V version and the 36V version of the standard Q100 are the same motor. I am not sure why `BMS Battery lists them apart.
You will never see 50 Kph(32 mph) with 2 Q100's, irregardless of what versions you use.
I have run 2) 328's @ 12S, 13S and 14S and they pretty much "hit the wall" at 13S(54V), which topped out at 28 to 29 mph. Adding more Volts above this did not increase the speed for me. To get to 50 Kph would require power levels that would put the motors at great risk.
I have used a pair of S12S's with a pair Q100 328's*(in 24"wheels) without "melting" anything, they are very "soft start" controllers.
But i swapped them out for several reasons. They are huge and 2 take a lot of space to mount and mounting 2 SLCD-3 displays created some problems. Also, they would not "read" the Voltage of either 11S or 12S Lipo, making the battery capacity gauge useless, although the one time I hit the LVC, it seemed correct.
And remember, "current control" only works in PAS.
For me, the 9-FET controllers from ELIFEBIKE(available in 17A and 23A)were a smaller, simpler solution. They are more or less as quiet and smooth as the sine-wave controllers.
As I said before, expect a top speed for two 328's @ 36V to be around 40 Kph.

 

[teklektik]

I have two 36V/10Ah batteries. So the choise of the batterie is already done.
...
I will rprobably use the same motor on for the front and back,
...
To set the ebike.ca simulator I have used the Q100 328rpm motor, with a.55.5V battery (to simulate the 24V motor version : 24V*37v/24v) and 15.3A controller (also to simulate the the 24V motor : 23A*37v/24v), and the bike loads are divided by 2 (‘custom frame’ and ‘custom weight’). That set gives a 53 km/hr max speed and a 8% road grade without overheating which is perfect for my usage.

You will never see 50 Kph(32 mph) with 2 Q100's, irregardless of what versions you use.
... expect a top speed for two 328's @ 36V to be around 40 Kph.

Motomech's top speed estimate is spot on.

Your simulator analysis for 2WD analysis is flawed which led to some bad projections. The simulator relies on intersection of the Motor Power curve (power developed not power consumed) and the Load Line - which is the power required to propel the bike at a given speed. 2WD analysis is simple for two identical motors/wheels/controllers - just locate the intersection of the Load Line and twice the motor power curve of a single motor. Easy peasy,

Here's a quick run with a little How-To and results that illustrate motomech's estimate:
2 x Q328, 25A controller, 36v, 230lb bike+rider = 25mph (40.5kph) top speed.


Adding the extra step to align the speed cursor as indicated will allow you to play with the parameters (throttle/grade/weight/wheel size/controller rating) as per normal to see what happens to your speed, current, and overheat times.

Remember that the leftmost part of the motor power curve before the discontinuous peak is the controller limited portion under high load (typically acceleration) so from the plot above, your motors are running at only 10.3A of the controller's configured max of 25A; flat out on the level, the controller limiting does not really have an effect on top speed. Even on a 7.5% grade, the controller limiting is not in play until you get the controller limit down to 15-20A. If you experiment, you can get a rough idea of a 'safe/safer' controller size for your climbing needs (no or slow overheating - if such a setting exists). In any case, as with a single motor, heat-wise things go wrong pretty rapidly with these little motors if you climb even slightly steeper than planned.

In any case, you can see your 2x10Ah batteries are going to be running at 1C at that speed (Battery Amps per motor = 10.3). Climbing something like your 7.5% incline will send the battery amps to about double that or 2C.

So - not surprisingly - two motors substantially improve your hill climbing and acceleration, ease your overheating issues, but will do very little to buy you more speed. It looks like what you have proposed will make a nice torquey bike, but not the speedy bike that you wanted....

 

[sange]

Motomech, Teklektik,
Thanks for your answers.
Your graphical method makes perfect sense. Dividing the bike loads by two, as I did, gives the exact same results, the advantage being that you can directly read the input and output data in the table.
I agree the Q100 24V/201rpm @ 36v is very similar in performance to the Q100 36V/328rpm @ 36v. However I don’t think they are the same motor. I red somewhere that the 24v/201rpm has a one stage gear where as all the other Q100 versions have a two stage gear. I never had a chance to check by myself.
But I was simulating the Q100 24V/328rpm overvolted to 36V with a 23A controller. And I still believe it can push me to 50 km/hr. A member of the French Cyclurba forum has equiped his bike with two Q100 24v/328rpm overvolted to 30V, and this configuration is capable of 48 km/hr : http://cyclurba.fr/velos/2277/greencity-madrid-bimoteur-1400w-45km-h.html
If possible, and I think it is, I would use one LCD-3 for the two controllers. As the batteries are 10S, there should be no issue with the data readings and set up.
As said, the no risk option is two Q100 36V/328rpm @ 36v / 15A which will give the same performance than the two Q100 24v/328rpm @36V 23 A up to 40 km/hr. But the Q100 24v/328rpm @ 36v shows additional performance above 40 km/hr till the current slows down in the low 50's km/hr. For some reasons, I cannot capture the simulator screen to show this.
The issue with this very fast configuarion is the 600W required that the Q100 gearing might not like. Any experincec of broken gears with Q100's ?
According to the simulator, there should be no overheating at full throttle from 0% to 8% road grade. I know their temperture caculation is basic and might not be very accurate.
Regarding the choice of controller, the 9 mosfet from Elifebike might not be compatible with the LCD-3 of BMS Battery. So I prefer to order everything from the same supplier.
Agree my batteries will suffer with the 23A controllers although they can deliver it.

 

[motomech]

I give up.
Good luck.

 

[teklektik]

Your graphical method makes perfect sense. Dividing the bike loads by two, as I did, gives the exact same results, the advantage being that you can directly read the input and output data in the table.

It's actually Justin's method - this is the underlying idea used to ascertain the max speed. The red annotations above show how this technique is used in the standard 1WD solution. The condition shown by the green annotations arises when the cursor is scrubbed according to the instructions in yellow.

Again - your approach is valid, but your implementation (as you described) is not quite correct: The idea is to re-plot the Load Line to be power necessary to propel 1/2 the bike - but because of the underlying equations, simply cutting all the input parameters in half will not lead to one half the result. To make this work, you must divide both the mass and aero drag coefficient (CdA) by two, but leave the rolling resistance (Cr) unchanged.

Either approach, (scrubbing the cursor as in yellow annotation above) or manipulating mass and CdA, yield exactly the same tabular display values - there is no advantage of one over the other in that respect. However, (IMHO) the cursor solution is simpler, requires no special knowledge of the underlying CdA and Cr values, requires no knowledge of the underlying equations (to know which parameters to adjust), and is extendable to mixed motor solutions -- but different courses for different horses....

 

[John in CR]

If you want more speed on hills then you need more power...same torque X greater rpm. If you don't have heat issues on your hills now, simply increase the voltage. The KISS principle works wonderfully with ebikes.

 

[WhatcomRider]

Teklektik's analysis is spot on. If you enter CdA = 0.29 (half the mountain bike frontal area) and Cr = 0.008 (same as mountain bike rolling resistance) and custom weight = 52kg (half the mass) you will get exactly what the graph above shows for max speed. So now that I have revealed the magic numbers, either approach is quite simple to implement for analysis.

 

[d8veh]

Several people tried the Q100 at 22A and found that they didn't get past the end of their road. A 328 rpm one at 23A is really pushing it. The Q100H can take more current than the cooking version, but nobody has determined a sensible limit yet.

 

[sange]

Thank you all for your feedback. These are useful information.

I am a KISS addict in every thing I do. That's why I am planning to use my two 36V batteries and get two 24V / 328 rpm motor. It should give me a fast configuration.
To illustrate what I said erlier, I have simulated a Q100 36v/328rpm and a Q100 24v/328rpm, both fed with 36V battery and a 23A controller (see attachment).

What strucks me is that both configurations have the same performance from 0 to 32 km/hr. But the 24v/328rpm motor keeps running till low 50 km/hrs. So I do not see any reason why I should not use the 24V/328rpm motor version. Do you?

Using the LCD3 I can easly adjust the running parameters:
. Set a lower speed, for example in urban area,
. Set lower Amps in case of road grades exceeding 8 %, to avoid overheating and burning the motor.

So my only worry is with the mecahnical strength of the Q100 in particular the gearing. Has anyone experience a purely mechanical breakdown with a Q100?

 

[sange]

Dear D8veh,
You are right, running a Q100 at 23A requires some minimum cares.
The guy I was talking earlier runs his Q100s at 30A (!), but his bike is a 2WD therefore it passes the low RPM/low efficiency zone very quickly.
I am not planning to use my futur fast bike at full throttle, Max Amp all the time. It will rather rum most of the time at 70% throttle and 18 Amps, and only whhen the road conditions will allow it, I will run full throttle and max Amps.
Thanks.

 

[John in CR]

Dear D8veh,
You are right, running a Q100 at 23A requires some minimum cares.
The guy I was talking earlier runs his Q100s at 30A (!), but his bike is a 2WD therefore it passes the low RPM/low efficiency zone very quickly.
I am not planning to use my futur fast bike at full throttle, Max Amp all the time. It will rather rum most of the time at 70% throttle and 18 Amps, and only whhen the road conditions will allow it, I will run full throttle and max Amps.
Thanks.

The motor only sees phase current, which is often much higher than battery current, and partial throttle can actually cause higher spikes in phase current leading to more system stress despite lower performance. If your controller is programmable in a manner that you can also set the phase current limit, then using a lower phase/battery limit ratio can enable you to run at higher power through the mid range where motor power peaks while at the same time reducing the stress on the motor from phase current spiking high during the early parts of acceleration and at partial throttle. As you mentioned, cutting the load a motor sees in half by adding a 2nd motor enables higher power settings, so going 2wd means more than double the power is possible and still run your system at lower stress levels.

 

[d8veh]

The guy I was talking earlier runs his Q100s at 30A (!), but his bike is a 2WD therefore it passes the low RPM/low efficiency zone very quickly.

Who was that?
Are you sure that he didn't mean 30A total, i.e. 15A each?
I don't believe that anybody can run one at 30A.

 

[motomech]

In the last couple of months I've tried 4 different controllers on the frt. of my dual 328 Rocky mountain(24"whl.s).
Right now I have an early Grin\Infineon sm.6-FET, mostly because I had it laying around, it's sm. and I wanted to connect an old 2.3V SA CA that I have via Direct Plug-in. I thought it was a 20A controller, but it turned out to be a 25 Amper(I see 26A on the CA).
At 12S, it;s plainly too much. The motor as a nasty vibration that I'm sure is not good for it. At 11S, hot off the charger is about the same, but as the Voltage drops it smooths out, around 43-44 Volts. I really need to limit the current below 20A, but I'm still working on mating the CA SA via the DP cable to the controller. There is a problem if the throttle wire(Th on these old CA's, not ThO) is connected. I think I need to add a diode\resistor circuit for the throttle override to work.
The S12S which peaked at 24 Amps was smooth as could be, even @ 12S. Even at low throttle settings, these Sine Waves are noticably smoother and quieter than the Infineons.
I currently am using an Elifebike 17A 9-FET on the rear wheel and in terms of size, power, price and reliabilty seems to be the best match for my Q100. It is almost as smooth and quiet as a sine wave. but not much for features, just the 810 display.
I think the ELB 19A 9-FET would be a nice controller for the 201 motors and the H.

Note, I am refering to the mechanical capacity of the Q100 here. I don't use these motors hard enough or long enough to get them hot.

 

[sange]

D8veh,
here is the link of the guy who rides a Q100 24v/328rpm 2wd : http://cyclurba.fr/velos/2277/greencity-madrid-bimoteur-1400w-45km-h.html
Each motor is fed with 30v battery and 30 amp controller.

 

[sange]

John,
it's incredile how much current the motor connecting wire and plug can withstand. With the 23Amp controlle setting, it goes up to 61 Amp at start. With a more reasonable 15 amp controller, it is 51 Amp. Has anyone experienced melting plug or wire with the Q100 and or the BPM which, I think, is similarly equiped ?
Thanks.

 

[sange]

Motomech,
I am curious about your test with the 12S battery and S12S controller. Any drawback with this setting?
Thanks.

 

[d8veh]

D8veh,
here is the link of the guy who rides a Q100 24v/328rpm 2wd : http://cyclurba.fr/velos/2277/greencity-madrid-bimoteur-1400w-45km-h.html
Each motor is fed with 30v battery and 30 amp controller.

It doesn't quite add up. He's using S06S controllers. You can't get 30A out of one of those otherwise we'd all be using them.

 

[sange]

D8evh,
His S06S' does deliver 30 Amp each. The guy found out that the original shunt once modified with solder generates a lot of heat, up to the point that the solder melted away. So he changed the orignal shunt with an external shunt made of a copper wire. So it looks like when the S06S amp is pushed, a large part of the heat generated is coming from the shunt, and eventually the heat and/or the melted solder can destroy the controller.

 

[sange]

D8veh,
I forgot the link to the corresponding Cyclurba thread: http://cyclurba.fr/forum/156197/greencity-madrid-bi-moteur-n-a-marche-d-enfer.html?from=441&discussionID=8575&messageID=296337&rubriqueID=92&pageprec=

 

[d8veh]

Yes, I know he modified his shunt, but 30A from a S06S would melt it. As I said before, if it could be done, we'd all be riding round on Q100 and S06S at 30A.

 

[chas58]

s

I agree the Q100 24V/201rpm @ 36v is very similar in performance to the Q100 36V/328rpm @ 36v. However I don’t think they are the same motor. I red somewhere that the 24v/201rpm has a one stage gear where as all the other Q100 versions have a two stage gear. I never had a chance to check by myself.

You are right, they are similar, but not the same. Someone posted the internals here somewhere showing the difference a couple of years ago.

I have both. one is 200rpm24v at 36volts gives 300rpm, the 36v328rpm is obviously 328rpm. Measuring the two I got no load speads of 28 and 29mph respectively. Actual on the road speeds for me are 24 and 25mph respectively (although I do have a higher top speed for the 328 version). As I recall the 328rpm version felt a little more torquey at speed, while the 24v201@36v was a little smoother and quieter. But yeah, they are very similar to each other on the road.