Electronic Braking in PAS

[Solarman]

When riding in PAS, if I stop pedaling it feels like the brakes have been applied rather than the motor just stopping its assistance. I understand the motor is supposed to stop when you stop pedaling and/or when you apply the hand brakes, but I expect it to free-wheel and not slow down the bike as soon as I try to coast for a bit on level ground.

With similar electric motors on my giant-scale RC airplanes - in the 700-1000w range, there is a "brake" setting in the ESC (speed controller) that is user selectable to either on or off. With it "on", the motor acts as a brake, slowing the propeller when the throttle is closed. With it "off", the motor free-wheels with the throttle closed.

It appears that my XP has it's speed controller "brake" setting turned on, and I'm not particularly happy with that. When I asked Lectric CS about that they replied that "...applying the brakes is intended to turn off the motor." I understand that (and that the motor should also turn off when you stop pedaling) but it isn't what I was asking... I'm asking about the motor's behavior when it is turned off - in my case the turned-off motor acting as a brake rather than free-wheeling.

I'm not talking about normal friction here, but rather an obvious braking effect without either of the hand brakes being touched. And pedaling without PAS (level 0) this effect is not noticable, so there's nothing rubbing or binding that is slowing the bike and preventing coasting.

Anyone else experiencing this behavior? i.e., does it feel like the brakes are being applied when you stop pedaling in PAS? Or do you simply coast when you stop pedaling?

Bud

 

[Darceman]

The easiest way to check this is lift the back wheel off the ground and spin it. It should spin easily. I know that it feels like the brake is put on sometimes if your riding without power, it's the sheer weight of the bike and the fat tires. I ride mine 25% of the time at least without the power and it is a major difference without the power on. Especially if you're going up a very slight grade. Are you sure that's not just what you're feeling

 

[GeorgeXP]

Anyone else experiencing this behavior? i.e., does it feel like the brakes are being applied when you stop pedaling in PAS? Or do you simply coast when you stop pedaling?

Bud

Sorry it took me so long to reply, I received my XP about a week and a half ago and finally got a chance to see if mine had any dynamic braking as you discribed.... it did not.

I had the front tire in a Bikehand floor stand and made a lift for the rear that is basically a inverted "T" about 2 feet across the bottom and 13 inches tall. This inverted "T" supports the rear end under the bracket for the rear fender and has a screw with a rubber insulator on the top that sits in the hole of the bracket to keep it stationary with the rear tire about 1" above ground.

With the Battery OFF I gave the rear wheel a few good spins and watched/listened to it spinning down.... Sounded nice and free.
With Battery ON and Display OFF... Same.
With Battery ON and Display ON... Same.
With PAS1 motor kicked in and the Speed came up to 12.4mph, I stopped cranking, motor shut off... Same.

Anyhow, just thought I'd let you know what I found and how I did it.

George

 

[Solarman]

Thanks, George.

About the time I posted this issue Mother Nature dumped about 8" of snow on us, the temp dropped to sub-arctic and I haven't been able to try anything beside lifting the rear wheel and checking for any rubbing or other resistance - there was none...

My recollection was that this only happened (or that I only noticed it) at higher speeds - anything under about 12-15mph everything was normal and I could coast without any indication of braking. But at higher speeds the slow-down was quite apparent when pedaling was paused.

Maybe I'll cobble up a stand that will allow me to verify that it only happens at higher speeds...when it warms up some! The way the weather is now I think riding is finished until spring...

Bud

 

[Solarman]

I think I may have figured out what is going on here, and it appears to be the way the speed controller is programmed to operate. It seems that the PAS levels equate to a programmed speed - approximately 8mph for PAS 1, 12mph for PAS 2, 16mph for PAS 3, etc.

From a standing start, pedaling lightly (allowing the motor to do the majority of the work), you'll stabilize at about 8mph in PAS 1, 12mph in PAS 2, etc. Of course you can pedal faster, but you'll be doing most of the work and the motor will be idling at around 1A of current (I normally ride with the display set to show battery current, as the energy bar is essentially a voltmeter, and this gives you the best picture of the electrical parameters of the bike).

When I noticed the "electronic braking" I spoke about, I was in PAS 1 but pedaling harder and going faster than 8mph (or in PAS 2 going faster than 12mph). When I stopped pedaling there was a noticeable slowing down back to the speed programmed for the particular PAS I was in. Once the speed bled off to that speed, further slowing was what you'd normally expect.

I was keeping my PAS level lower as I learned how to operate the new bike for two reasons: to maximize the battery life (less current draw), and get more exercise! By increasing the PAS level to more closely match the speed I wanted to go, the "electronic braking" effect disappeared.

So I'm confident I've identified the reason behind my suspected gremlin, and will put this matter to rest unless anyone else has other ideas about this phenomenon.

Bud

 

[GeorgeXP]

I think I may have figured out what is going on here

Thanks for posting your follow-up. Hopefully it may help someone else who has the same question.

On Christmas day I did take my new XP down to our underground garage for a quick spin. I understood how the PAS on our hubs worked but was disappointed in how high the PAS1 was set at, I would have prefered lower ~5mph motor kick in speed. I suppose the way to look at it is that the PAS is only "Pedal Assist" (-sharing- the load) when you are pedaling at a speed above the current PAS level speed. As you found "there was a noticeable slowing down back to the speed programmed for the particular PAS I was in." Below that programmed level the motor is nolonger assisting, it's doing all the work.

For me this PAS is not a big deal because I bought it to be used Throttle Only most of the time. I currently drive a 1980 Puch Maxi Sport MkII moped. This is a true "Moped" as in Motor & Pedals and it has a top speed (with a good wind) of ~28mph. With it I'm stuck in the uncomfortable zone where I'm too small for the street and too big for the bike trails. So for me the XP is my replacement for the Puch as I will now be driving on the paved trails away from the cagers and the C2 20mph speed is just fine.

George