BPM power surges

[DBrown67]

Got my kit all installed and sorted with pedal assist working. Really happy with how it works and rides. I have 5 assist levels and have found that level 1 seems like it's not there. It's probably very faint and my 95kgs might be a defining variable. Level 2 is just about discernible. Level 3 is where I'm at. I definitely feel a boost and just adjust gears accordingly. Rarely use the throttle to flat out a steep incline. I try not to use it much as I hear it's basically full power so range suffers.

But the only niggle I have right now is that as I'm cruising along at level 3 on the flat... enjoying the scenery at 10mph... the motor will sometimes just go into a surge or boost mode for a few seconds. It's as if the throttle has been opened fully for a bit. It only lasts a few seconds and I can catch it quick by pulling a brake lever to cut the power. I just don't want this to happen if I'm near the waters edge on a towpath... could be a comedy result!

It really is a minor issue at the moment. It's not something that worries me unduly as it does it quite rarely. But when it does do it it can take me by surprise. I would like to sort it if at all possible.

 

[Charliefox]

Got my kit all installed and sorted with pedal assist working. Really happy with how it works and rides. I have 5 assist levels and have found that level 1 seems like it's not there. It's probably very faint and my 95kgs might be a defining variable. Level 2 is just about discernible. Level 3 is where I'm at. I definitely feel a boost and just adjust gears accordingly. Rarely use the throttle to flat out a steep incline. I try not to use it much as I hear it's basically full power so range suffers.

But the only niggle I have right now is that as I'm cruising along at level 3 on the flat... enjoying the scenery at 10mph... the motor will sometimes just go into a surge or boost mode for a few seconds. It's as if the throttle has been opened fully for a bit. It only lasts a few seconds and I can catch it quick by pulling a brake lever to cut the power. I just don't want this to happen if I'm near the waters edge on a towpath... could be a comedy result!

It really is a minor issue at the moment. It's not something that worries me unduly as it does it quite rarely. But when it does do it it can take me by surprise. I would like to sort it if at all possible.

Depends on what type of throttle is fitted. Full throttles do vary output according to how much you twist them.All 3 of mine do at least. One could equally argue that on a basic PAS system you are constantly using whatever power level you choose, wether up, down or on the level. Whereas releasing thottle when not needed is done without thought and no need to look at your controller. If your hand gets tired holding the throttle, I see there are now a sort of plastic clip for mopeds etc, that lightly hold it in whatever position you require. I might try one.

 

[Woosh]

But the only niggle I have right now is that as I'm cruising along at level 3 on the flat... enjoying the scenery at 10mph... the motor will sometimes just go into a surge or boost mode for a few seconds.

Try unplugging the throttle to isolate the symptom.

1) does it happen at any other level at that 10mph speed? eg at assist level 4 or 2?
2) does it happen at 9mph or 11mph?
3) does it happen when you are at certain gear (eg 5th) and at 10mph?
4) can you reproduce it easily?

 

[DBrown67]

Unplugged the throttle cable today and went on a few miles ride. At level 3 assist it did it again exactly same as before for duration and power. So I plugged cable back in and changed to level 2 assist. Didn't really enjoy this so switched to level 4. It did it again but for only a second and with much less pronounced power. Eventually switched to level 2 again on the flat and it did it again similar to level 4.

It really needs more miles to be fair as today was around 10 miles only. I certainly cannot reproduce it easily. It happens when cruising along at a steady pace so it seems totally random.

 

[Woosh]

using the motor simulator at ebikes.a for your bike + rider weight =120kgs and BPM motor

http://www.ebikes.ca/tools/simulator.html?bopen=false&motor=MBPM&mass=120&axis=mph

the motor load for 10mph is only 76W.
This is very little for the BPM motor, when you are on assist level 3, the bike reaches its set speed very quickly.
when it does, the controller reduces the current until the speed drops, then when the speed drops a bit, it increases the current again.
That may be what you have seen.
The throttle or a torque sensor don't have wavy responses.

 

[DBrown67]

I think I may need to use level 2 more. I just love the push off feel level 3 gives from a standstill.
I would like to reiterate that this is not a major problem I am having. I wouldn't want to put anyone off trying a kit. I suppose I'm being picky in wanting perfectly smooth transition all the time. It really is a couple of seconds when it does it and with brake sensors fitted is quickly caught if you wanted to.