pedal assist way too fast!!!!

edavinci

1 mW
Joined
Jan 12, 2012
Messages
13
Hello, I'm new to the discussion, but all af your topics helped me build my e-bike. Thank-you. :D My set up is Bafang BPM 350W front hub, EcityPower KU93 Controller and 36V 10AH LIFEPO4 battery. Is it normal to pedal slightly and rocket to 40kmh? :shock: I was expecting slow pedal= some assist, fast pedal= much assist. Is there a way to set this up properly??? Thanks for your help.
 
Yup, I've got a throttle, and it works well. Do you think I need to power off and "teach the controller" again?
 
Well, that is a first; a post about an ebike going too fast!
 
Don't get me wrong, I love the speed! But I'd rather feather the power with the pedals.
 
here is my Pedal sensor at this link:
http://www.bmsbattery.com/ebike-parts/49-pas--pulse-padel-assistant-sensor.html
 
Do I need to plug in the motor hall sensor wires? Jack Xie at ECityPower said no; but there could be a some Chinese/english difficulty. thanks for your help.
 
edavinci said:
here is my Pedal sensor at this link:
http://www.bmsbattery.com/ebike-parts/49-pas--pulse-padel-assistant-sensor.html


That sensor can't measure the amount of force you're applying to the pedals, it can only measure if your crank is turning or not.

If it's turning, it's going to apply whatever throttle it's set to apply.
 
liveforphysics said:
... it can only measure if your crank is turning or not.

If it's turning, it's going to apply whatever throttle it's set to apply.
Is that how it works? I thought it is a little smarter than that. I was under the impression that it measures how fast the crank is turning (cadence) and apply the throttle accordingly.
 
A good pedal assist system has to have a torque sensor, that is the only way its use can be intuitive.
 
Those cheap pedal sensors are crap. Not only do you just get full throttle but they don't always turn off fast enough and if you are stopped and move the pedals for any reason the bike will try to take off. Not a good thing if you are at a stop light.

I would figure out how to run the bike without them if I were you.

Gary
 
The pedal assist sensor works by passing a disk with embedded magnets by a hall sensor. As each magnet passes you get a pulse. I would hope that the controller has been programmed to give assistance proportional to the frequency of pulses it receives. So as long as it does actually vary the assistance in this way and is not just an on/off switch, then it is is likely the sensor is receiving too many pulses (or assuming everyone peddles really slow, or the PAS disc is not correct for the controller) and therefore ramping it up to full power straight away. You can test how it works by spinning it up on the pedal sensor with the wheel off the ground to get a feel for how it functions.

So you can either use a higher gear so the pedal sensor is getting less pulses and you are doing more of the work with less assistance. You could try removing half of the magnets in that pedal sensor disc which will trick the controller into thinking you are turning the cranks at half the speed. Or, the best solution, ditch the pedal sensor and use the throttle to control exactly how much throttle you want and pedal as much as you want. The last option is much nicer if you have a controller with cruise, that way you aren't always riding the throttle, you set it, leave alone and pedal as hard as you want and at the speed you picked.
 
thanks cellman. Man I love the speed and acceleration :D , but it was my impression the motor speed would be somewhat proportional to the pedal speed. I can pedal slowly with no assistance, until about 20 pedals per minute ( one every 3 seconds) then the motor rockets to maximum rpm. I have a Ecitypower KU93 controller. what will fix this problem? :(
 
@edavinci

Most pedal assist systems are simplistic, the motor speed is not proportional to pedal speed.

The controller is just programmed to detect pedal motion and whether it is in the forward direction.

Most that I have seen don't account for RPM or torque. They are designed to meet laws and regulations in different countries, they're not designed to make the bike more intuitive or usable. One of the few positive consequences of the simplistic pedal assist is that you do get at lest some exercise if you wouldn't otherwise pedal at all and your battery range usually increases compared with relying on the throttle to start you from stop.

If you want to keep using it, I would suggest you get a 3 speed switch like this:

http://www.bmsbattery.com/ebike-parts/53-three-speed-switch-kit.html

If you don't want to use the throttle, set the 3 speed switch to Low, start pedalling and once you're ready, change to Medium then High speed.
 
Ypedal said:
The only system i know that works correctly for this type of thing is BionX... but expect to shell out a buttload more money for it !! ..

my suggestion is to get rid of the pedal sensor and install a handlebar mounted throttle..

I agree with Ypedal, just use a throttle. A 3 speed switch is also a good option, you'll get full speed, but if that speed is restricted to something sensible, then it's no harm if it shoots up to restricted full speed. I personally like to use cruise to do this, you dial in the speed you want on the throttle, hit cruise and pedal as much or as little as you like.

I wouldn't say all controllers with PAS are all or nothing as you have found, they were probably just a bit lazy when they were programming the software on that model/range you are using. My experience with PAS is that they seemed ok on low powered bikes, but were a bit useless on anything with any sort of power or speed.
 
VoiceCoils, I'll buy the three speed switch, for $1, how can you go wrong. :wink: Which reminds me, my kit came from BMSBattery.com, all was good except the battery charger arrived with a european plug and 200-260volts input. I could not charge the battery until an electrician friend split my input cable into two plugs. My kitchen recepticles are on two different circuits, so the two plugs were 236V, problem solved :lol: I was told I could get a proper charger from BMSBattery, but I had to buy some more stuff; well now I'm going to spend $1 and get a charger...how sweet is that!!! :p Back to the pedal assist....Cell-man I think you are right, the programmers are lazy, proper proportional pedal assist is easy to program, just include it with the controller. I've learned how to deal with the set-up. In traffic, at a light, I start with thumb throttle, this keeps the assist off. When I'm up to 5kmh then i let go the thumb and the assist rockets me to 40kmh. When I need to slow down, I can back pedal or I can bump the thumb throttle. The KU93 also has a cruise wire, how does this work?
 
GrayKard said:
Those cheap pedal sensors are crap. Not only do you just get full throttle but they don't always turn off fast enough and if you are stopped and move the pedals for any reason the bike will try to take off. Not a good thing if you are at a stop light.

I would figure out how to run the bike without them if I were you.

This is exactly what almost scared my wife away from ebikes altogether. I bought a small folder with a 250w bafang that she was trying out -- it was her first time on an ebike. At traffic lights she was used to re-setting the pedals for optimum leverage. This would cause the pedalec sensor to trigger the motor. I think it was throttle independent. It's not a very natural feel. After about 2 minutes of riding, we went home.

Later on, I disconnected the sensor and eventually she started enjoying it -- throttle control of motor only.
 
Yes, I gave up on mine, as you say...max speed with slow pedalling, and then it takes a second or so after you stop pedalling for the pedal assist to stop feeding power tot he motor. Throttle position makes no difference

Forget it as a bad job
 
I just added an electric motor, control system and battery to my wife's bike so that we may ride together. As others said in this thread, the pedal assist was too strong.

At the suggestion of one of the posters, I disabled the pedal assist by just unplugging it. My wife loves this arrangement. Adding thrust through the twist grip while she pedals works perfectly for her.

Thank you all for the great advice!
 
Good that a topic that is 8 yrs old helped you. :D

You can make the PAS working good if needed. Yet, I agree that a throttle is the most intuitive control.
 
Throttle is good, it gives you the assist you desire.

PAS is mostly bad. Only torque measuring pas is OK and then only OK, not good.

Poorly implemented pas is high risk and dangerous.

Throttle is not high risk and dangerous, it works like your car, truck, suv, motorcycle, scooter, etc.
 
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