Motor + Pedal

[RossG]

Hi all..
I'm new to the world of E-bikes so please bear with me. I've just purchased a 20 in folding E-bike, 250w hub motor 10 amp battery. Having tweaked the settings on the LCD display I find it reaches around 19 mph on pas level 5, I'm no youngster so that's plenty enough speed for me (on a folder at least).

Now if I put the bike on a work stand and turn the crank like heck I can of course get the speed well beyond it's 19mph powered limit, but is the motor still assisting me ?
If the speedo reads 25mph am I actually using the amount of effort it takes to add 6mph to the max motor speed, or am I really turning the rear wheel 25mph myself.
The reason I ask this is that it does seem to take quite a lot of effort to add that 6mph, certainly more than just coasting at that speed.

Ross..

 

[wheeliepete]

If the motor cuts at 19 mph or has reached the max. speed it can physically turn at under electrical power, then you are providing all the effort above that speed. On the flat or slight downhill you may find it fairly easy to maintain your higher speed, but a slight incline will need considerably more effort to do so. Once your speed drops to below 19 mph it will then become alot easier because the motor is now assisting you again.

 

[RossG]

All that make sense of course. The bit that puzzles me is if the motor keeps turning no matter how fast you can pedal and you're cycling at 25mph, then it's supplying 76% of the power (I think), the other 24% is down to your peddling. Perhaps it just me but it just seemed to require a fair bit of cranking to reach 25mph on the display, but as I said this was a quick test on a bike work stand it might feel different on the road.

 

[Nealh]

The motor has two speeds a load and unload speed, the load speed takes in to account the motor & electrics efficacy loss which is about 20 - 24% on the road.
At no load as in your test there is little efficacy loss so hence the extra 24% speed.
What you see is normal and most if not all all e-bike drive efficacy falls in to this range.

 

[RossG]

Again this all makes sense. I note that some motors will literally switch off when at max speed then you are on you're own until speed drops to assist level. My basic Bafang hub motor just keeps turning regardless so how much assistance it's supplying to the overall speed I don't know.

 

[Nealh]

The speed the hub assists to depends on voltage, rpm winding and the assist level it is set to as well as the controller.

My Bafang Cst 270rpm wlll max out at 24mph @36v, though does cut out at lower speed if I set the assist speed lower.
My Bafang Bpm 201rpm max's out at about 19.5 mph.
The Yose cst I have is about 280rpm and max's out similar to the Bafang cst, but at 48v the Yose has seen 28mph with my 46/11 gearing.

 

[vfr400]

Your Bafang motor will turn as long as you pedal. It has a maximum speed, may be 20 or 22 mph. If the wheel turns faster than that, the clutch disengages so the wheel can turn at 25 mph but the motor is spinning at 20 mph without giving any power until your speed drops down to the motor's maximum speed. Additionally, the motor's power ramps down as it speeds up. You might get maximum power at something like 15 mph, ramping down to nothing when the motor maxes out on speed.

Turning up the current on the controller has no effect past that point of maximum power, so it won't increase your maximum assisted speed. It only increases the power below around 15 mph.

 

[RossG]

All understood... Now my humble e-folder has a maximum speed setting in the display of 35mph although obviously the bike won't go that fast, but that number is irrelevant because the motor cuts out at say 20 odd mph anyway ?