Whats normal performance wise?

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merganser   10 mW

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Whats normal performance wise?

Post by merganser » Aug 28 2013 3:52pm

I've just finished building my first ebike, and have now done a few miles on it. I'm a bit disappointed with the performance, so would like to canvass opinion on whether this level of performance is normal, or whether their may be something wrong with the setup.

The specs are: Bafang CST 500W 36V motor, KU123 controller and a 36V 15Ah battery (12S Headway 40152 LifePO4 cells plus 30A continuous BMS). I'd estimate the combined bike & rider weight as being approx 310 lbs.

I am only getting 15-16 mph without pedalling on the flat (measured using GPS) using 700C - 40mm tyres. I was expecting a bit better, maybe 20 ish mph. Certainly the assistance is noticeable (I was able to climb a pretty steep hill in a much higher gear than I would have otherwise) but I can't help feeling that the level of assistance doesn't justify the weight and increased pedalling effort when unassisted. It just feels a bit limp - if this is normal for 500W, I'd hate to try a 250W euro setup!

I don't have a cycle analyst or any other way of monitoring the current, but after climbing a couple of miles of steep hill (I was also pedalling), the motor was only luke warm and the controller was not noticeably warm at all. Is this normal?

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pdf   10 kW

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Re: Whats normal performance wise?

Post by pdf » Aug 28 2013 4:19pm

Yes, normal for that power system. In this speed range, the speed is proportional to the voltage. For more help up a hill, you are going to need more power.

If your equipment is flaccid, power up! More volts to go faster, more power to go up a hill. Your power can be limited by:

1) the current your controller can supply to your motor
2) the current your battery can supply to your controller, or
3) the heat your motor can shed

Your motor is, I think, a small geared hub motor. You want to be careful about the power to a geared hub motor because they don't generally shed heat as fast as direct drive. At very high power levels, the gears can be damaged. Not sure about the controller. BMSbattery lists that controller as compatible at 36 or 48 v and rates it as 500 watts, but it should be rated by current. Assuming this is at 48V (?), that is 10 amps. At 36v that is around 13 amps. This is almost certainly where an upgrade would be helpful. Your battery, assuming it can feed 1C continuously, should be good to 15 amps. At 36v that is around 540 W. This whole system is build around 500W. IF (and that is a big if, you need someone who has one to chime in) this motor can take it, I think a higher rated controller is the first thing that you would notice. At some point, your battery will be the weak link, but I am pretty sure it should be good up to at least 1.5C for quite a while if not continuously (at least several minutes), and this would be 750W. For bursts, you can probably get 2C. If speed is a bigger issue than power, get a 48v battery. Your speed will go up proportionally more or less at this speed range, so you will see around around 30% more speed, if this is sufficient. You don't require a new controller if you just want to go faster on the flats.

Find out from someone here if your motor will take 750-800W. If so, you can get another controller if you want power or another battery if you want more speed or both if you want both and your motor can take the power. That is a pretty small (but well known) motor though so don't go overboard or you will fry it. This is a great little stealthy setup but is not designed for speed or power. It would be awesome for some applications, particularly for people who like to pedal a lot.
Last edited by pdf on Aug 28 2013 4:30pm, edited 1 time in total.
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Re: Whats normal performance wise?

Post by gogo » Aug 28 2013 4:24pm

If you can find out which model Bafang you have it will be easy to look up its RPM/volt. Then you can test the no-load speed to see if its spinning up to the proper RPM.

At the least you could compare the no-load to loaded speed. 15-16 MPH sounds close to what would be expected from 36V 500W. Assuming everything is working properly, a 48V battery would be an easy route to 20 MPH.
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Re: Whats normal performance wise?

Post by DAND214 » Aug 28 2013 4:48pm

Those controllers are auto switch from 36 or 48v. In order to go faster you need 48v.

In most cases 36v is dead just like lead abtts, even they are still pushing it. That keeps the power leval near the limits in most places.

For more power and maybe a little top speed. You can open the controller and add a small amount of solder, to the shunt, that controllers the amps drawn.

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Re: Whats normal performance wise?

Post by merganser » Aug 28 2013 5:25pm

OK, thanks for the responses - sounds like the performance is fairly normal.

According to the specs, the battery & BMS should be good for 2C (30A). I'll see if I can borrow a clamp on current meter to try and find out how much current it draws.

This thread http://endless-sphere.com/forums/viewto ... =2&t=37853 suggests the KU123 should be good for 20 - 30A (rather more than 500W), so I doubt if it is the problem.

Just a thought though - the controller has wiring for a 3 speed switch which I haven't fitted, could this (or something else) be limiting the power?

gogo - I think the CST motor only comes in a 270 rpm version, I can't accurately measure it but I'd say the unloaded speed is around 270 rpm. The speed under load is approx 180 rpm (calculated from speed and wheel circumference).

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Re: Whats normal performance wise?

Post by dogman dan » Aug 28 2013 5:35pm

I've heard of some controllers having a default to the middle speed if the switch is not installed. That could be part of your problem.

Anybody know which two wires in his switch plug he should try putting a jumper on?

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Re: Whats normal performance wise?

Post by -dg » Aug 28 2013 7:55pm

dogman wrote:I've heard of some controllers having a default to the middle speed if the switch is not installed. That could be part of your problem.

Anybody know which two wires in his switch plug he should try putting a jumper on?
No, and it's probably wired wrong anyway. But it is easy to test. There should be a black wire, probably in the middle position. That will be ground. Just put a jumper wire from ground to each of the other positions, one at a time and run the motor to see how fast it is.
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Re: Whats normal performance wise?

Post by Samd » Aug 28 2013 11:30pm

pdf wrote:Yes, normal for that power system.
Doesn't sound right to me at all, even if the CST is a mid wind speed. Very timid.
On a regular code 10 BPM with a KU123 (not shunted) at 36V30 amps you'd expect precisely 34kph in a 700C.
And the myth about the BPM being a small hub motor, and KU123 about heat shed/not being very powerful is about 2 years out of date. :roll: I don't know where you're getting your info from pdf?

Merganser, Is there a Bafang code on your CST?
The KU123 will happily take 35A with a shunting and shove it at 63V into the BPM to handle 2200Watts - that's well over 120Nm at the rear axle. :evil:

I'd plug in a 3 speed switch and make sure you aren't in slow mode. Several recent KU123 controllers I imported were set to mid-speed only - might be worth a try.
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Re: Whats normal performance wise?

Post by shenzhen_ex » Aug 29 2013 12:10am

merganser wrote: ......I am only getting 15-16 mph without pedalling on the flat (measured using GPS) using 700C - 40mm tyres. I was expecting a bit better, maybe 20 ish mph. ...... Is this normal?
I had a similar problem with a similar motor and different controller. Here is what I did to solve it.

THE PROBLEM:
I have a Bafang CST 500W 48V motor on the rear, and a Bafang 500W 48V on the front. When I first got them working together the rear motor was much slower than the front. And I had to use the rear controllers reverse function to get the rear wheel to rotate in the forward direction. The front alone would get me to 40 kph but the rear alone only got me to 20 kph (I have 24" wheels). I knew this speed difference was not right for motors and controllers that are almost exactly the same. And I ruled out the 3 speed switches causing the difference because they were working fine.

POTENTIAL SOLUTION:
After searching on-line I found someone else had this issue (not on ES). They explained that if the motor runs at half speed that I just need to connect the white "self learn" wires on the controller for a second and it would fix the issue. I did that and it solved my speed difference and it was no longer running in reverse. The "self learn" are hall sensor position I think. BTW when I connected the "self learn" wires the bike lurched forward about 1-2 feet, so be careful! :shock:

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Re: Whats normal performance wise?

Post by d8veh » Aug 29 2013 3:56am

I have two of the 500w Bafang CST motors with KU123 controllers on my bikes, and I've built two others for friends. The controller is 30 amps, so power is not a problem. No-load speed is 24mph with 26" wheels (270rpm), so something is clearly wrong with your setup. The only thing I can think of is that you've joined the speed-limit wires. The white wires should not be connected.

The KU123 is switchable between 48v and 36v, but it's not automatic. You have to join the red wires for 36v and disconnect them for 48v. Be careful, if you forget to connect them for 36v, your LVC will be 38.5v, so you'll only get half the range from your battery.

The KU123 is fullu automatic regarding phase and hall sequence. There's no reverse direction connector, nor self-learning procedures. You just connect everything and it works. I've never known or heard of one get anything wrong.

Once you've got it running properly, you can try the three-speed switch connector. Normal operation is when nothing is connected, so if you don't connect anything, your bike should be doing 22mph on the road with 26" wheels and proportionally faster with 700c. When you join the black middle wire to the green one, you get aboyt 10% speed boost. When you join the black to the blue, it cuts maximum speed to 15 mph. Can you confirm that you have nothing connected?

Please report back whether you had the white wires connected, or whether you need further help. You don't need to go to 48v. Your present setup should give you about 24mph on the flat.

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Re: Whats normal performance wise?

Post by merganser » Aug 29 2013 5:08am

samd - I will post the information printed on the motor this evening. I looked for a code previously and could not find anything like code 10 or 11 (the BPM I have has an 11 marked). IIRC it is marked with 27, but I'm not sure whether that is a motor code or something else.

d8veh - I am currently running with the red wires connected (36V) and the white wires disconnected. I am running the motor with the sensor wires connected (just matched colours for phase & hall wires, runs smoothly), I only have a throttle connected, nothing connected to the PAS sensor or 3 speed switch connectors.

I would appreciate any help you can offer, though I think the first step will be to swap the controller (I bought a spare KU123) and see if that makes a difference.

Does the controller remember the last 3 position speed switch setting? i.e. if it was somehow set to low speed, then the switch was removed would it stay in low speed mode or revert to normal speed?

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Re: Whats normal performance wise?

Post by pdf » Aug 29 2013 8:36am

Samd wrote:
pdf wrote:Yes, normal for that power system.
Doesn't sound right to me at all, even if the CST is a mid wind speed. Very timid.
On a regular code 10 BPM with a KU123 (not shunted) at 36V30 amps you'd expect precisely 34kph in a 700C.
And the myth about the BPM being a small hub motor, and KU123 about heat shed/not being very powerful is about 2 years out of date. :roll: I don't know where you're getting your info from pdf?
https://www.bmsbattery.com/ebike-kits/5 ... n-kit.html

If this is not the motor and controller the OP has, then it is all irrelevant. I don't have any experience with this motor/controller. Based on the website above, which has the same stated specs as the OP's system, wrt power/voltage. In the picture, the motor is barely larger than a geared hub.

Is there more recently link to this motor and controller?
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Re: Whats normal performance wise?

Post by merganser » Aug 29 2013 8:47am

Yes, that is the motor & controller I have though the main picture is wrong (shows smaller motor).

The motor is larger than a geared hub, its about 18cm in diameter, see here:

http://www.szbaf.com/product.asp?id=2

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Re: Whats normal performance wise?

Post by pdf » Aug 29 2013 11:10am

merganser wrote:Yes, that is the motor & controller I have though the main picture is wrong (shows smaller motor).

The motor is larger than a geared hub, its about 18cm in diameter, see here:

http://www.szbaf.com/product.asp?id=2
if the motor is not the geared hub, then forget comments. The system is clearly different than the one spec'd on the page. Also, I did not know you could get a hub motor that would take a rear cassette. Opens up some options.
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Re: Whats normal performance wise?

Post by merganser » Aug 29 2013 2:01pm

Samd wrote:
pdf wrote:Yes, normal for that power system.
Merganser, Is there a Bafang code on your CST?
The KU123 will happily take 35A with a shunting and shove it at 63V into the BPM to handle 2200Watts - that's well over 120Nm at the rear axle. :evil:

I'd plug in a 3 speed switch and make sure you aren't in slow mode. Several recent KU123 controllers I imported were set to mid-speed only - might be worth a try.
The only writing on the motor is as follows:

CST 36V500W 26
1307 1060

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Re: Whats normal performance wise?

Post by merganser » Aug 29 2013 2:11pm

OK, I've tried swapping the controller for the spare one - no difference.

I borrowed a clamp on current meter from work and the peak current drawn is typically around 23A though I did see it go as high as 30A briefly. When up to speed on the level (16 mph) the current draw is about 8A - 10A.

After shorting the black & green wires on the 3 speed switch connector, the speed on the flat has increased to 19 - 20 mph.

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Re: Whats normal performance wise?

Post by amigafan2003 » Aug 29 2013 2:39pm

merganser wrote:After shorting the black & green wires on the 3 speed switch connector, the speed on the flat has increased to 19 - 20 mph.
That was it then - the controller was set to mid speed. All sorted then. From the codes on your motor (1307 = code 13) that means you have a slow(ish) wind motor and 19/20mph is bang on for that motor @ 36v in a 26" wheel. If you want to go faster, you'll need a higher voltage battery.

@ PDF the Bafang CST is a BIG geared motor. It's in the same league as a MAC motor - capable of peaking at 2000watts.
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Re: Whats normal performance wise?

Post by amigafan2003 » Aug 29 2013 2:41pm

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Re: Whats normal performance wise?

Post by pdf » Aug 29 2013 3:41pm

amigafan2003 wrote:
merganser wrote:After shorting the black & green wires on the 3 speed switch connector, the speed on the flat has increased to 19 - 20 mph.
That was it then - the controller was set to mid speed. All sorted then. From the codes on your motor (1307 = code 13) that means you have a slow(ish) wind motor and 19/20mph is bang on for that motor @ 36v in a 26" wheel. If you want to go faster, you'll need a higher voltage battery.

@ PDF the Bafang CST is a BIG geared motor. It's in the same league as a MAC motor - capable of peaking at 2000watts.
Have never seen the Mac geared motor, but have one of the eZee V2 sold by ebikes.ca. It climbs like a goat. At 48v it has a top end of around 26 or so, similar to this one it sounds like. It is recommended to keep the power below 900W on the eZee, but 900W is a lot on that motor. Good to hear merganser got it sorted out.
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Re: Whats normal performance wise?

Post by merganser » Aug 29 2013 3:44pm

amigafan2003 wrote:That was it then - the controller was set to mid speed. All sorted then. From the codes on your motor (1307 = code 13) that means you have a slow(ish) wind motor and 19/20mph is bang on for that motor @ 36v in a 26" wheel. If you want to go faster, you'll need a higher voltage battery..
I guess so, though I am using 700C wheels with 40mm tyres rather than 26". Code 13 is 230 rpm I think, which is odd because I thought the CST motor only comes in a 270 rpm version. Can someone else with a CST motor let me know what code theirs is?

Anyway, I now think it is working normally - 20mph is enough, so I won't bother going to a 48V battery.

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Re: Whats normal performance wise?

Post by gogo » Aug 29 2013 4:25pm

Good to see you've got it sorted out. Was the current draw you mentioned (23A-30A) measured after you jumpered the black/green wires?

The rating nomenclature in this industry is interesting. I assumed that a controller labelled 500W meant the maximum output, not the average.

Have your performance expectations been met now? You should have more torque available now, as well as a higher top assist speed.
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Re: Whats normal performance wise?

Post by merganser » Aug 29 2013 4:53pm

No the 23-30A was before shorting the green/black wires. I had assumed the the 500W referred to the maximum continuous wattage, but I suspect it varies a lot between manufacturers.

I'm reasonably happy with the top speed on the flat as I was wanting a bike rather than moped, but the speed does drop off quite markedly with even a slight hill. Uphill performance is fine provided you pedal a bit though.

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Re: Whats normal performance wise?

Post by Samd » Aug 29 2013 5:39pm

pdf, I think you need to refamiliarise yourself with the power capabilities of recent geared hubs. A lot has change. And the very first sentence you posted in this thread led the OP to think you knew precisely about that system. Try to imagine your ezee (I run them also) at twice the power.

If you read half way down you'll see Kepler replacing his Crytalyte on his stealth fighter with something that will surprise you:
http://www.electricbike.com/stealth-hot-rod/

The old gear issues are no more.

Glad to see the OP worked out the speed switch. I had five new KU123's arrive in stock yesterday - all set to default mid speed this time from the factory with no switch connected.
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Re: Whats normal performance wise?

Post by d8veh » Aug 30 2013 4:33am

Something is still wrong. It should be faster than that. 24mph should be the result. I suspect that your throttle is faulty, and it isn't giving full throttle. Put your cycle computer on the back wheel to get the no-load speed, then disconnect the throttle and short the red to the signal (white?) wire to see if it spins faster, or try a different throttle if you have one. If you haven't got a cycle computer, you can stuff a bridge wire up the back of the throttle connector between the red and white. Run it at full throttle, then make and brake the connection, and you'll hear and see any change in speed. You'll get instant full throttle when you join those wires, so be careful.

The number 27 on the motor might indicate 270 rpm, which is the normal speed of these motors.

Amigafan, the three-speed switch doesn't work like that on the KU123. It's not like the Lyen/infineon ones where you programme a speed percentage. It changes the timing on position three to get the boost. It doesn't do anything when running sensorless.

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Re: Whats normal performance wise?

Post by pdf » Aug 30 2013 9:16am

Samd wrote:pdf, I think you need to refamiliarise yourself with the power capabilities of recent geared hubs. A lot has change. And the very first sentence you posted in this thread led the OP to think you knew precisely about that system. Try to imagine your ezee (I run them also) at twice the power.

If you read half way down you'll see Kepler replacing his Crytalyte on his stealth fighter with something that will surprise you:
http://www.electricbike.com/stealth-hot-rod/

The old gear issues are no more.

Glad to see the OP worked out the speed switch. I had five new KU123's arrive in stock yesterday - all set to default mid speed this time from the factory with no switch connected.
Nice custom frame, by the way.

The newer, larger geared motors are a different breed of animal, and I thought the eZee was impressive. Twice the power would be pretty amazing. I recently debated going with one of the larger geared hubs vs a DD. In my case, I figured the DD would be marginally quieter, but these new large geared hubs are pretty amazing. In the end, I went with a DD because in my situation, quieter is better, but it was close. And the lighter weight of a geared motor compared to a DD is nice. The noise level is pretty low on the eZee and being able to pedal with no cogging is nice also.

How does the Bafang compare to the eZee with gear buzz? In the Stealth mod video, the gear buzz is noticeable, but the sound can be exaggerated in videos.
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