Would a middrive PAS activate itself?

I'm thinking about adding pedal assist to the Ebike I'm wanting to build, which is the middrive type. However, it got me thinking that if I start to pedal, and the motor starts helping me pedal also, I would have to counter the motor's power to make it stop, if I was to use this kind of pedal assist sensor. With this said, recently, I have used a middrive city bike which had pedal assist on it (and only PAS, no throttle), so it means that it is totally possible to have PAS on a middrive bike. So how does pedal assist sensors work in middrive bike in order to not "make the motor drive itself"?

In the same subject, how exactly does PAS levels make the motor respond when you pedal? Does it continually adjusts the voltage in order to keep the power the same?

EDIT: I changed the title because this one is more appropriate.

Might be able to address a couple of your questions, but not very technical ones.

But first, I have two trikes equipped with Bafang BBS02 crank drives that have both PAS and a throttle. A few days ago after switching one of the BBS02 systems from a trike I'm going to sell to a new (to me) trike I was testing things out with the powered wheel off the ground and after hitting the throttle while in PAS mode and then letting off on the throttle it slowed down (the powered wheel) but never stopped running. Finally figured out there was enough drag in the freewheel that the chain kept the pedals going around which kept the motor running, just like you were concerned about. But when actually riding the trike when you stop pedaling the freewheel in the drive system prevents the pedals from overpowering your feet and the motor stops fairly quickly. Plus, in the BBS02 you can also stop the motor faster (if you are not still pushing on the throttle, but just using PAS) by either giving a slight backwards nudge to the pedals or pulling on a brake lever that has a disconnect switch built into it, plus several other ways you can set your bike up to cut power.

For your last question, there are two basic types of PAS. One type just delivers a constant level of power without any concern as to your pedaling effort. The more complex ones are tied to your effort and will increase or decrease power as dictated by the system to keep your effort constant based on the level you chose. Someone more knowledgeable will have give more technical answers if you need them.

EDIT: I probably should have mentioned that most mid-drive or crank drive systems are set up with a standard freewheel at the driven hub (so you can coast without the chain moving) and another freewheel at the crank (so that you don't have to pedal just because the motor is running) and another freewheel at the motor (so you don't have to turn the motor if you just want to pedal for a while).

Putting more simply, stop pedaling and PAS stops putting in power. Or grab a brake.


On better systems, the PAS sensitivity can be adjusted in the display programming. I'm not sure bafang allows this, but I bet it does. The reason I hated PAS so much for so many years, was poor PAS programming. So thank god you can tune them now.

Nothing worse than PAS that won't start when you need it quick enough, then whams you with too much power unexpectedly. Some PAS has throttle over ride, which means you can just throttle off from a stop, then start pedaling in high gear later. But without a throttle, PAS can be a tricky ride if the programming does not suit your pedaling style/ cadence, etc.

Same on the stopping side, you want that motor to stop the instant you stop pedaling, not 3 seconds later. Some I rode would keep going after you stop pedaling longer than I'd like. But that problem is easily solved there, since all PAS I ever saw included brake cut offs. So just a tiny touch of brake handle turns off the motor instantly. So you can stop the motor with a brake handle, before a pad even touches a wheel. Just a flick and the motor goes off instant.

Alright thanks for the replies guys! I guess a slight pressure backwards would do the trick or, if not, i might just use the ebrake as you stated. I'll have to test that out once I finish my build. But from your answers it seems to not be that big of a deal, even with a middrive system.

Just beep the brake handle and it stops. It doesn't have to actually brake, just move the lever a bit and make the switch inside work.

Or stop pedaling, you don't have to back it up, just stop rotating, or pushing.

If you tend to fiddle with your foot position at the stops, have a brake handle pulled.

Proprietary mid-drive kits all have an arrangement for using pedal assist. If you make your own kit, you can use a free-wheeling crank that you can get from Cyclone-tw and fit the PAS on the left side.

http://www.cyclone-tw.com/order-chainwheel.htm