Bafang conversion kit : Recovery from over-speed is slow

[hengist]

Heyo,
I have a 250 W Dillenger front hub kit on a 10-y-old hybrid commuter which has transformed my commute, but:

When I sail down a hill which puts the road speed over the limit of 15.5 mph, the motor freewheels (great), but when I start up the next hill the controller waits until the road speed is down to 11 - 12 mph before it restores torque. This is a time of several seconds, I'm guessing this is some kind of safety feature, but it's a pain when you have to wait (with pedals spinning) for the system to forgive me for enjoying gravity assist. The motor is a Bafang 36 V BPM, the control head is a C965.

Has anyone found a work-around for this behaviour? I currently manage the situation by _braking_ down hills to avoid over-speeding, rather than having the controller bonk at the bottom and leave me struggling up the other side; I consider this less hazardous than having no drive (my knees won't allow me to supply much pedal pressure).

 

[anotherkiwi]

I wait until the speed drops below 23-22 kph before I start pedaling again. If the PAS detects pedal movement before 25 kph it acts as you describe. The problem is with the controller, the easy way to fix it is to remove the speed limit...

 

[vfr400]

Disconnect the speed sensor. It probably won't release the speed limit, but it should solve your problem and make the motor spin whenever you pedal.

 

[hengist]

I wait until the speed drops below 23-22 kph before I start pedaling again. If the PAS detects pedal movement before 25 kph it acts as you describe. The problem is with the controller, the easy way to fix it is to remove the speed limit...

Thank you.

I tried this this morning, and it worked as described: no pedaling until the speed drops below the limit. The drive recovery was soft, as one would expect when the bicycle is close to the limit. This was the one combination I hadn't tried. The hill in question is a railway bridge which I more usually circumvent by using a crossing on the other side of the station, but when the crossing is used by the trains, impatient me turns away and uses the bridge.

Case closed; grateful.

 

[hengist]

Disconnect the speed sensor. It probably won't release the speed limit, but it should solve your problem and make the motor spin whenever you pedal.

Thank you.

This sounds like I'd have to pull a pin or two from the motor's connector, if you mean I should disconnect the motor's speed sensor. This may have a useful side-effect: drive will be immediate whenever correctly-phased pulses are seen by the controller from the cadence sensor, and so taking off from a halt will be easier. It may also have the opposite effect; with the controller seeing no speed input from the hub, it won't supply current. Frankly, I don't know; all my knowledge in this field is in much larger vehicles and although many of the issues scale well, fork-trucks don't have pedals.

Either way, I was hoping for a less technically intense intervention, and the simple change in riding habit (don't pedal until the speed is below 15.5 mph) has solved it.

Good idea, but not to my taste; thanks for the reply.

 

[Flumpet]

I have the Dillenger conversion too, and have this problem. i've also changed the speed limit settings to 20 mph, thinking that this would solve the problem, but i'm not convinced it did. will try the not peddling bit.

How would i disconnect the speed sensor?