Over voltage Q100 36V to 48V -- it's a good idea?

[casainho]

Hello.

I am afraid of powerful Bafang BPM 48V 500W because it broke my fork, 2 times. Now I want to go with a rear motor. My mechanic tell me my bicycle rear dropouts are fragile and don't advice me put a Bafang BPM 500W, I agree with him.

What I am looking for: get a no load RPM of ~44kmh (I want and I will pedal to get near that velocity); small weight motor for having small kinetic energy when compared to the Bafang BPM 500W (I drive before 1 year with small Cute-85 motor).

I am buying from BMSBattery and I am thinking on the Q100 36V 350W motor (2kg weight, small motor):

- Q100 36V have 275 no load rpm which should give on 26'' wheel 33km/h. But I want the 44km/h (I also have only a 48V battery) so maybe if I run the motor at 48V I will get an increse speed of 1.3 --> 33*1.3 = 43km/h??

Is there any problem to overvoltage that motor (I drive on mainly flat places)?? What wattage it will be?

In alternative I could use the Q128 48V, however I don't know his no load rpm...

--------------------------------------------------
Edit on October 2012:
I bought the motor Q100 350W 36V 328 RPM. With my 48V battery full charged (at 54.6V), in freewheel the motor gives 62Km/h!

I am using this motor (running with the 48V battery and controller KU123) since some months and all is working great!! -- please see here a blog message with pictures and details: http://www.massacriticapt.net/?q=node/1647

 

[Sunder]

Commenting on this thread because I want to know as well.

From threads on this forum and others, I've read that people have put 750w reliably through it, and 1000w through it for short bursts with no problem. However, there was no indication of what voltage and current combination was used.

I'm surprised 500w is causing you problems. Had you considered getting a soft start controller? One that slowly ramps up power to reduce shock to the drop outs?

 

[casainho]

From threads on this forum and others, I've read that people have put 750w reliably through it, and 1000w through it for short bursts with no problem. However, there was no indication of what voltage and current combination was used.

Please share with me the links for that others forum messages.

I am thinking using the KU93 controller that theoretical limits to 22amps, so, 1056watts at 48v. KU93 is the lowest power controller for 48v on BMSBattery.

 

[pchen92]

Hi,

here are my rear dropouts with a BPM




Sorry for the quality.
A friend of mine was running a rear ninecontinent 5x12 @ 100V+ and 45A without torque arms (aluminium dropouts) before it gets stolen. You just have to make sure the nuts are enough tight. I won't do it at this power level though. But with a BPM that's okay.

The Q100 will suffer at 45km/h. And you won't obtain 43km/h at 48V. More like 39-40km/h.

The KU93 will do fine with the BPM. If you want more power, stay with the KU123.

 

[motomech]

I run a MXUS 3 kg. motor on 48V/17.5A with no problems and I don't think running the Q100 on 48V would be a problem.
A 22A controller would be at the upper limit of "safe", but given that you are a strong on the pedals and your terrain is mostly flat, I think you would be OK.
I have read that your cassette has an 11 tooth low gear, so if it's 9-speed, you would want to get a 9-speed DNP free wheel, which will fit your dropouts with the Q100.
The Q100 "fast wind" on 48V should give you 39 to 41 Kph, flat, no pedal and no wind. With a 44/11 final gear, you should be able to add 2 to 4 Kph to that. Later, you could install a 48T chainring up front to drop your cadence some.
I'm not sure if you can get the DNP 8 or 9-speed free wheel in Europe, but if you decide to get it from one of the Ebike stores, get their torque arm as well.
I know you don't want to use the BMS Battery's torque arms again. I believe that these let you down. I believe that the Ebike CA store will get you the fastest shipping.

Here is a link to a couple of Q100 installs using a 9-speed free wheel,

http://endless-sphere.com/forums/viewtopic.php?f=3&t=32364&start=15

Lastly, the Q100 motor cover is easy to remove, you might want to have mechanic install a temp. sensor inside.
I think this will get you the bike you are looking for.
I admire your persistence, so hang in there.

 

[Sunder]

endless-sphere.com/forums/viewtopic.php?f=3&t=13998&p=538535&hilit=q100#p538535

There's one link for 12s (44v, or 51v hot off the charger)

There were a few more, but I'm on my phone. Sorry about that. If I can get on my PC, I'll get some others.

 

[dogman dan]

I suggest you do not repeat your front fork test when you put on a rear motor.

 

[d8veh]

I have a 24v Cute Q100 in my folding bike, which I run with 12s lipos (50 to 44v). It'll do 20 to 22 mph on the flat without pedalling and it's very quiet. I only do such speeds for up to 5 minutes at a time so as not to overheat it. However it doesn't appear to get very warm. It also climbs hills very well due to the smaller wheel which gives it lower gearing. IIRC it's a 201 rpm motor for 26" wheel. I guess a 36v one in a 26" wheel would be about the same. The internal gears are Nylon/delrin and don't look too strong, so I'd say no good gor jumping.

Regarding the broken forks: The larger shaft of the BPM prevents the shaft from going deep enough into the drop-outs. It's very important to file the drop-outs deeper so that the shaft is central to the dimple otherwise the drop-out will break when you tighten the nuts because of the uneven pressure of the washets which will exert a huge sideways force on the drop-out. I've see one break like that even beforr the giy fired up his motor.

I run front BPMs in two bikes with aluminium forks and torque arms with no problems, although I don't jump.

 

[motomech]

Yes, I had issues with the "Lawyer's Lips" as well, but for a different reason. On my Dirt Jumper dropouts, I only had to deepen the recess a m/m or two to "center" the axle, but the Lawyer's Lips were still in the way. And the axle lenght on the MXUS was not great enough to use C-washers and still fit my Ebike CA torque arm and the nuts.
So I used the flat side of a standard Dremmel disc and ground the Lawyer's Lips off.

D8veh, curious, I believe you are running 36V and limited amps on your front mount BPM.
Would you be comfortable running 48V and a controller in the 30 to 35A range on that install?

 

[casainho]

With a 44/11 final gear, you should be able to add 2 to 4 Kph to that. Later, you could install a 48T chainring up front to drop your cadence some.

I am already with 48/11. But 11 on cassette and now I need to buy the 11 on freewheel, and yes, I just bought it from ebikes.ca (I bought one more pair of arm torque from BMSBattery and I have 1 arm torque here from my last order).

On some long flats, I almost got 40km/h with the Cute-85 motor for wheel 16'' but installed on the 26'' wheel. I went almost to the "end" on the gears 48/11.

I suggest you do not repeat your front fork test when you put on a rear motor.

Yes. I plan to use the same torque arms. If the dropouts break while riding I think will be more safe than if dropouts on front wheel would break.

I just bought the "Q100 36V350W Rear Driving EBike Hub Motor - RPM : 328". Other options could be rear Q128 48V 500W of 328 RPM or rear Bafang 48V 500W(this is out of stock for now). I decided to not go with Q128 because have 145mm spacing dropouts and I believe it could be a problem on my bicycle. Also 328 RPM would give me only 39km/h. Also Q128 is 3kg while Q100 is 2kg, so, less kinetic energy.
I am in the hope Q100 36V and over voltage to 48V may give me at least 45km/h with me pedaling. Jack from BMSBattery tell me it is a motor of 328 no load rpm, if that is true, it could potential give 50km/h???

My question is (that I will get answered after get the motor and test it): will I get a bit more speed and power with this motor and setup (KU93 controller) when compared with my last one (Cute-85 24V 250W for 16'' wheel installed on a 26'' wheel, no load RPM of 315 at 24V, KU63 controller)??

 

[Russell]

I use a "328 RPM" (@36V nominal) Bafang 250W motor in a 700C rim w/40mm tire (27.5"). With a fresh 12S LiPo battery my no-load speed is 37.5 mph (60.5 kmh) @ 50.3V. On the road my top speed is 29 mph (46.8 kmh) using a 20A controller. I don't know what battery you're using but if it's 16S LiFePO4 I would think the extra voltage would allow you to match this result with a 26" tire (a smooth one anyway). I also ran the same motor/battery with a 15A controller and the top speed was limited to 27.5 mph (44 kmh). Just remember at these speeds you'll be running the 250W motor at its limit. It'll take it on the flats but watch out for hills which can quickly overheat little motors and more so if you've already heated them up nicely.

-R

 

[casainho]

I use a "328 RPM" (@36V nominal) Bafang 250W motor in a 700C rim w/40mm tire (27.5"). With a fresh 12S LiPo battery my no-load speed is 37.5 mph (60.5 kmh) @ 50.3V.

Do you know if the no load RPM is really 328 as stated on BMSBattery site?

On the road my top speed is 29 mph (46.8 kmh) using a 20A controller. I don't know what battery you're using but if it's 16S LiFePO4 I would think the extra voltage would allow you to match this result with a 26" tire (a smooth one anyway). I also ran the same motor/battery with a 15A controller and the top speed was limited to 27.5 mph (44 kmh).

1. We can limit the used power by the motor by controlling the current (with constant voltage)??

2. Is the velocity only dependent of voltage and the torque dependent only from the current?

I have with me the following controllers:
- KU63 24V 250W 12A
- KU93 48V 450W 22A
- KU123 48V 500W 30A

My battery is 48V 10Ah Li-Ion NiCoMn.

 

[d8veh]

D8veh, curious, I believe you are running 36V and limited amps on your front mount BPM.
Would you be comfortable running 48V and a controller in the 30 to 35A range on that install?

I think that the most important point is that everything should fit nicely and then the nuts can be done up tight, which then allows the torque arms to do their job. I've run one of my other bikes with a rear BPM at 40 amps and 12s lipos but found it too fierce. The torque kept breaking traction at the back, which caused me to high-side twice. That's why I cut the power down to about 25 amps. 40 amps would be OK on roads, but the problems I had were on rough cycle tracks with loose gravel and mud. I'm thinking that 48v and 30-35 amps might be a bit much for a front. I get a bit of wheel slippage on very steep hills at 36v and 25 amps. I don't believe it would be too much of a problem for the forks as long as they have nice thick drop-outs and everything is installed correctly, but, if anything comes loose or shifts, you could get sudden failure sometime in the future. There's always a risk, but a good engineer can see what's in front of them and make it work. I wouldn't recommend it for anybody who doesn't have this sort of nouse.

 

[motomech]

I use a "328 RPM" (@36V nominal) Bafang 250W motor in a 700C rim w/40mm tire (27.5"). With a fresh 12S LiPo battery my no-load speed is 37.5 mph (60.5 kmh) @ 50.3V.

Do you know if the no load RPM is really 328 as stated on BMSBattery site?

On the road my top speed is 29 mph (46.8 kmh) using a 20A controller. I don't know what battery you're using but if it's 16S LiFePO4 I would think the extra voltage would allow you to match this result with a 26" tire (a smooth one anyway). I also ran the same motor/battery with a 15A controller and the top speed was limited to 27.5 mph (44 kmh).

1. We can limit the used power by the motor by controlling the current (with constant voltage)??

2. Is the velocity only dependent of voltage and the torque dependent only from the current?

I have with me the following controllers:
- KU63 24V 250W 12A
- KU93 48V 450W 22A
- KU123 48V 500W 30A

My battery is 48V 10Ah Li-Ion NiCoMn.

From another post,

Here is a short list of geared mini-motor no-load[@36V] rpm numbers.
Not "chiseled in stone" and certainly not a definitive list, but I think they are accurate.
There is no difference between front and rear models where both "slow" and "fast" winds are offered.

MXUS[also called the Mini-might]
Only one wind offered- 250 rpm

Ananda[Cute] 36V/350W Q100 motor as listed on the BMS Battery site.
'201' "slow" wind- 230 rpm
"328" Fast" wind- 275 rpm

Bafang 3 Kg. motors, QSWXH, etc.
"201" "slow" wind- 201 rpm
"328" Fast" wind- 328 rpm

These last numbers are interesting, as they are the only mini-motor no-load numbers that appear to be accurate on the BMS Battery site.
Perhaps these were the only two motors that were actually tested and the rest of the Mini motors were lumped into these two specifications.
Close enough , logical in a non-logical way.

I'm also now thinking that the 24V/250W Q100 motors have no-load numbers[@ 36V] equal or close to the Bafang numbers listed above.

QUOTE- "2. Is the velocity only dependent of voltage and the torque dependent only from the current?"- END OF QUOTE

Pretty much, but higher current can help maintain a higher speed at less than no-load speeds when presented with headwinds or hills.

 

[casainho]

Ananda[Cute] 36V/350W Q100 motor as listed on the BMS Battery site.
'201' "slow" wind- 230 rpm
"328" Fast" wind- 275 rpm

I am in talks with Jack from BMSBattery and he tells me they will send me a 328 RPM motor.

Jack/BMSBattery already offered me 1 pair of arm torque after I broke the 1st time the fork. Also they did refund me 2 times after I changed my ideas, like not buying Bafang 500W BPM rear.

 

[Russell]

I use a "328 RPM" (@36V nominal) Bafang 250W motor in a 700C rim w/40mm tire (27.5"). With a fresh 12S LiPo battery my no-load speed is 37.5 mph (60.5 kmh) @ 50.3V.

Do you know if the no load RPM is really 328 as stated on BMSBattery site?

On the road my top speed is 29 mph (46.8 kmh) using a 20A controller. I don't know what battery you're using but if it's 16S LiFePO4 I would think the extra voltage would allow you to match this result with a 26" tire (a smooth one anyway). I also ran the same motor/battery with a 15A controller and the top speed was limited to 27.5 mph (44 kmh).

1. We can limit the used power by the motor by controlling the current (with constant voltage)??

2. Is the velocity only dependent of voltage and the torque dependent only from the current?

I have with me the following controllers:
- KU63 24V 250W 12A
- KU93 48V 450W 22A
- KU123 48V 500W 30A

My battery is 48V 10Ah Li-Ion NiCoMn.

I did not buy my Bafang from BMSBattery and it wasn't advertised as a "328 RPM" model however in practice I have found it spins at 9.1 rpm's/volt hence 328 rpm no-load at 36V (nominal). With my battery it spins at 458 rpm no-load at 50.3V which I derived from the no-load speed of 37.5 mph (60.5 kph) using the formula;

RPM = 37.5 mi/hr x 1 hr/60 min x 5280 ft/mi x 1 rev/7.2 ft

Top speed depends first on the motor windings which deliver a fixed RPM/V. So supply X number of volts and it will spin at Y speed, supply 2X voltage and it will spin at 2Y speed. My Bafang was advertised as a "24V" motor but all that means is it was meant to power a bike to about 25 kph on 24V. I run it at double that voltage and get roughly double the speed. On the road the top speed depends on the load and the ability of the battery and controller to supply the power required to match the load.

So to answer the other question; yes you can limit top speed by limiting the power output of the controller but it's not the best way to do it. Since it takes a certain amount of power to reach a certain speed if you limit current, and thus power output, you will limit the top speed. Taken to the extreme if I wanted to limit my bike to about 20 mph I'd get a controller that draws a maximum of about 7A. In practice however this combination would feel quite under-powered producing a peak power of under 350W.

With your battery and motor the KU93 and the KU123 would produce the same top speed though I would not recommend using a 30A controller with a Q100 motor. Even a 22A limit is probably a bit high with a 48V battery but if you don't have steep or long hills the Cute motor should survive. If the 24V KU63 could take 48V its 12A max rating would likely limit you to a top speed of 25 mph (40 kph) or less. While experimenting with modifying the shunt on a controller I limited it to 13A and while it felt less powerful on the low-end for assist it was OK.

The simulator at ebikes.ca is a great tool to see what a given motor/controller/battery combination can be expected to deliver. Unfortunately the simulator doesn't have every motor but I found the EZEE 20" selection to be a good stand-in for my Bafang since it's a geared motor which spins at the same 9.1 RPM/V as my Bafang. The Ezee is a larger motor than my 250W Bafang but it provides a very good model for it just the same.



-R

 

[casainho]

I did not buy my Bafang from BMSBattery and it wasn't advertised as a "328 RPM" model however in practice I have found it spins at 9.1 rpm's/volt hence 328 rpm no-load at 36V (nominal). With my battery it spins at 458 rpm no-load at 50.3V

I believe my motor is equal to yours, 328 RPM @ 36V.

At 48V it may have 436RPM, 52km/h!!! Seems to much since I am looking for maximum of 44km/h. I wonder what will be the efficiency.

This makes me asking this: cruise control/throttle control only the current of the motor? like, on a 22A controller, half throttle means 11A?? If so, wasn't better a control of the speed instead of the power?

On the road the top speed depends on the load and the ability of the battery and controller to supply the power required to match the load.

Yes, but this make me think how this relates to the efficiency.

With your battery and motor the KU93 and the KU123 would produce the same top speed though I would not recommend using a 30A controller with a Q100 motor. Even a 22A limit is probably a bit high with a 48V battery but if you don't have steep or long hills the Cute motor should survive. If the 24V KU63 could take 48V its 12A max rating would likely limit you to a top speed of 25 mph (40 kph) or less. While experimenting with modifying the shunt on a controller I limited it to 13A and while it felt less powerful on the low-end for assist it was OK.

I wish there as an OpenSource controller with:
- possibility to configure the maximum current.
- possibility of cruise control but with constant control of speed(automatic control of current) and not constant power.
- possibility to control ramp of acceleration.
- Bluetooth for output by wireless of speed, current, voltage, power, efficiency and on the fly configuration of current -- this information can be seen/controlled on Android and other smartphones.

I created a new forum message for this Smart Controller.

 

[Russell]

Remeber that "no-load" speed is the speed the motor spins when the wheel is off the ground, it's not the speed you can expect on the road. As I said my "no-load" speed is 60.5 kph but my top speed is 46.8 kph. From what I can tell your motor should give you the target speed you desire.

The majority of ebike throttles are simple voltage control devices and don't directly control the power output. When you crack the throttle from a stop, even half-way, the current and the power will spike sharply, often to maximum. The bike will accelerate and when you reach cruise speed the power output of the motor will equal the load (the load being the combination of rolling resistance, aerodynamic drag and gravity if going up hill). The power drawn from the battery will be higher of course due to system inefficiency.

Efficiency is a tough subject because of the variables involved. It's best when talking efficiency to take pedaling out of the equation. On a percentage basis figuring just power output over power input a controller will be most efficient at full throttle because it isn't doing any pulse width modulation. Controllers however are very efficient at doing their job so the difference between part throttle and full throttle efficiency is minimal, a percent or two. If you view efficiency as the lowest power consumption then riding slower rather than faster provides the best efficiency. At low speeds the load is much lower, the motor is working less and using less power. Then's there's efficiency under load which is rather complicated. Because hub motors are single speed they only operate at maximum efficiency only over a small range. On the flats with no wind when the motor reaches maximum speed it will generally also be at maximum efficiency, again on a power out/power in basis. When additional load is applied such as a headwind or a hill the speed will drop and power output will increase to match the load. The motor will fall out of the sweet spot and efficiency will drop. Apply too much load and the motor will stall with all of the applied power just heating the windings with efficiency at zero.

So for maximum system efficiency you want to pick motor/battery/controller which will provide the cruise speed you desire and run it at full throttle. For lowest power consumption you want to keep that target cruise speed on the low side. And if you want to use the very least power you'll keep speed low and contribute with pedaling.

-R

 

[casainho]

Remeber that "no-load" speed is the speed the motor spins when the wheel is off the ground, it's not the speed you can expect on the road. As I said my "no-load" speed is 60.5 kph but my top speed is 46.8 kph. From what I can tell your motor should give you the target speed you desire.

You get 46.8km/h on flat and pedaling, right?

The majority of ebike throttles are simple voltage control devices and don't directly control the power output. When you crack the throttle from a stop, even half-way, the current and the power will spike sharply, often to maximum. The bike will accelerate and when you reach cruise speed the power output of the motor will equal the load (the load being the combination of rolling resistance, aerodynamic drag and gravity if going up hill). The power drawn from the battery will be higher of course due to system inefficiency.

So, this means that if I choose to stay at half of throttle, my velocity will vary depending on the load variations (wind, up hills, etc). I wish the velocity could keep constant and the controller would manage the power output to motor to keep the velocity constant.

For example, I could decide to drive at 35km/h by adjusting the throttle to that (while my maximum possible could be 45km/h).

 

[d8veh]

I wish there as an OpenSource controller with:
- possibility to configure the maximum current.
- possibility of cruise control but with constant control of speed(automatic control of current) and not constant power.
- possibility to control ramp of acceleration.
- Bluetooth for output by wireless of speed, current, voltage, power, efficiency and on the fly configuration of current -- this information can be seen/controlled on Android and other smartphones.

I created a new forum message for this Smart Controller.

For any controller you can adjust the maximum current by adding solder to the shunt, which can give up to about 50% increase. It;s also possible to reduce the current by filing the shunt although I haven't tried it yet because it's much easier to do it via software with a Cycle Analyst or Speedict. Also it's possible to get a programmable controller, where you can set many parameters by software.

The KU93 and KU123 have exactly the cruise control you want, where, when activated, it controls the speed by adjusting the current to keep constant same speed, or you can do the same with a normal throttle if you can hold it still, or you can use a 10K potentiometer instead of a throttle, which works as a constant speed cruise control.

Controlling the ramp of current requires an additional device. This one by Gwhy is very cheap to make and program. If you ask him nicely, I'm sure he'll send you the code for it if you can't make your own.
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=33963&hilit=smoothing+throttle&start=15#p493593

The last thing that you ask for with bluetooth is available from Speedict. Exactly what you ask. It can limit speed, current and temperature; provide battery, speed and distance information and has a whole load of other useful features including the one I like most: If you get stopped by the police, you can adjust the governor settings from your phone to reduce the speed and power while they're examining the bike, so that if they try it, it'll be gutless. They won't know it has a Speedict because it'll be hidden next to your controller, and even if they did see it, they wouldn't know what it was.
http://www.speedict.com/
big thread but worth reading:
http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=22919&hilit=speedict

 

[casainho]

For any controller you can adjust the maximum current by adding solder to the shunt, which can give up to about 50% increase. It;s also possible to reduce the current by filing the shunt although I haven't tried it yet because it's much easier to do it via software with a Cycle Analyst or Speedict. Also it's possible to get a programmable controller, where you can set many parameters by software.

Adding solder or filling the shunt(s) seems difficult to predict the changes and even more difficult to verify the final value.

The KU93 and KU123 have exactly the cruise control you want, where, when activated, it controls the speed by adjusting the current to keep constant same speed, or you can do the same with a normal throttle if you can hold it still, or you can use a 10K potentiometer instead of a throttle, which works as a constant speed cruise control.

Yes, I used last year the KU63 with cruise control and I verified that KU93 and KU123 also have the function. But maybe I am wrong, because I always used full throttle, but seems to me the controller only controls the current/output power as constant and not the velocity... or I am wrong?

And does the velocity limit really verifies the velocity limit value e keeps that as constant or some power value instead?

Controlling the ramp of current requires an additional device. This one by Gwhy is very cheap to make and program. If you ask him nicely, I'm sure he'll send you the code for it if you can't make your own.
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=33963&hilit=smoothing+throttle&start=15#p493593

I would prefer this one, no programming, simple and cheap.

The last thing that you ask for with bluetooth is available from Speedict. Exactly what you ask. It can limit speed, current and temperature; provide battery, speed and distance information and has a whole load of other useful features including the one I like most: If you get stopped by the police, you can adjust the governor settings from your phone to reduce the speed and power while they're examining the bike, so that if they try it, it'll be gutless. They won't know it has a Speedict because it'll be hidden next to your controller, and even if they did see it, they wouldn't know what it was.
http://www.speedict.com/
big thread but worth reading:
http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=22919&hilit=speedict

I will need to inform my self about that device.

 

[Russell]

You get 46.8km/h on flat and pedaling, right?

So, this means that if I choose to stay at half of throttle, my velocity will vary depending on the load variations (wind, up hills, etc). I wish the velocity could keep constant and the controller would manage the power output to motor to keep the velocity constant.

For example, I could decide to drive at 35km/h by adjusting the throttle to that (while my maximum possible could be 45km/h).

My top speed of 46.8 kmh is with a freshly charged 12S LiPo battery on the flats with no wind and no pedaling.

If you keep a constant throttle position yes your speed will vary depending on wind and hills. The only way to keep speed constant is to vary the throttle as conditions change and even then you can experience wide speed variances if the loads are outside the motor's capabilities.

I haven't tried my KU93 controller yet on the road but the CRUISE function on the "universal" controller from BMSBattery I'm using now only holds the throttle position so it does not maintain speed as conditions change. Yes power output will change as the load changes but speed will vary. It's nothing like the cruise control on a car.

We get so used to maintaining a constant speed in our cars that we forget the only reason we can do that is cars have an overabundance of power available compared to what it takes to maintain a constant speed, even on the highway. So yeah if maintaining a constant speed is important then you either need a high reserve of power, something your motor won't have, or ride at a lower speed at part throttle and adjust as necessary to maintain that speed...or just let the speed vary and help out with pedaling when it drops!

-R

 

[d8veh]

Adding solder or filling the shunt(s) seems difficult to predict the changes and even more difficult to verify the final value.

Yes, I used last year the KU63 with cruise control and I verified that KU93 and KU123 also have the function. But maybe I am wrong, because I always used full throttle, but seems to me the controller only controls the current/output power as constant and not the velocity... or I am wrong?

And does the velocity limit really verifies the velocity limit value e keeps that as constant or some power value instead?

Adding solder is quite predictable. You need a wattmeter or ammeter to measure the current without solder; then add a bit and check again the current; then you can estimate how much more you need to get the current you want. You can do it in small steps if you want to be accurate.

The KU 63, 93, 123 all use the throttle as a speed controller, and so do most other controllers. You can see this if you replace the throttle with a 10k potentiometer. You can set it to say 25kph and it will try and hold that speed. the bike will slow down a bit when you go up a hill or into a strong wind, but the controller will feed in more amps in an attempt to maintain the speed. The more you slow down, the more amps it will give up to the maximum. If you pedal faster than 25kph, the amps will decrease. I don't use normal throttles any more. All my bikes have 10k pots instead, which I find much easier to control the power and very good if you want to add pedal power. You set the speed you want to go and then pedal as hard or easy as you want, and the speed hardly changes but you see the amps change instead.

 

[casainho]

We get so used to maintaining a constant speed in our cars that we forget the only reason we can do that is cars have an overabundance of power available compared to what it takes to maintain a constant speed, even on the highway. So yeah if maintaining a constant speed is important then you either need a high reserve of power, something your motor won't have, or ride at a lower speed at part throttle and adjust as necessary to maintain that speed...or just let the speed vary and help out with pedaling when it drops!

-R

I am learning with my KU63 and i verified with my oscilloscope that with cruise control, it just defines a constant duty cycle/pwm value. It doesn't adjust the duty cycle if i put load on the motor, hence it always low the speed when i put load.

 

[rafeh1]

Hello.

I am afraid of powerful Bafang BPM 48V 500W because it broke my fork, 2 times. Now I want to go with a rear motor. My mechanic tell me my bicycle rear dropouts are fragile and don't advice me put a Bafang BPM 500W, I agree with him.

What I am looking for: get a no load RPM of ~44kmh (I want and I will pedal to get near that velocity); small weight motor for having small kinetic energy when compared to the Bafang BPM 500W (I drive before 1 year with small Cute-85 motor).

I am buying from BMSBattery and I am thinking on the Q100 36V 350W motor (2kg weight, small motor):

- Q100 36V have 275 no load rpm which should give on 26'' wheel 33km/h. But I want the 44km/h (I also have only a 48V battery) so maybe if I run the motor at 48V I will get an increse speed of 1.3 --> 33*1.3 = 43km/h??

Is there any problem to overvoltage that motor (I drive on mainly flat places)?? What wattage it will be?

In alternative I could use the Q128 48V, however I don't know his no load rpm...

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Edit on October 2012:
I bought the motor Q100 350W 36V 328 RPM. With my 48V battery full charged (at 54.6V), in freewheel the motor gives 62Km/h!

I am using this motor (running with the 48V battery and controller KU123) since some months and all is working great!! -- please see here a blog message with pictures and details: http://www.massacriticapt.net/?q=node/1647

some questions
1. best place to order q100 motor
2. what kind of controller (sensored or sensorless) where did u buy?
3. you mentioned 11t freewheel in rear please explain i thought smallest freewheel is 16t for these motors.