Not particularly high power but faster ebike?

[GarethJ]

Getting on well with a yosepower 36v kit on a 700c bike with fairly tall gears....

However, I'd like to go, just a tad, faster. Recently rode a 48v version in a 26" frame and that's not really what I'm looking for but doesn't top out quite so early. Maybe a 48v in a 700c wheel?

Basically, I'm happy enough with about that level of power, but would like a "system" that provided less torque lower down but tops out at higher than the ~25mph.

More broadly, I'd like to know, in basic but technical terms, how ebike setups work. I.e, DC from the battery, into the controller which uses some wizardry to convert that DC into what? Varied DC to an EC motor? Any sensible resources I could peruse to get a more in depth knowledge...?

Thanks for any thoughts!

 

[GarethJ]

Rode my little 36v, 350w, rwd, 700c on full charge today and I think I might have the answer. That's about the sort of performance I was hoping for so, my thoughts are, that, the same wheel/motor but with a 48v battery and controller should add enough to the top end to let me get towards as fast as I can reasonably pedal, while at the same time, not being an overly large motor/battery unit.

Would have to be confident the motor could cope with the added voltage though.

 

[GarethJ]

Back onto thinking about this recently as have acquired a yr old 48v battery with some cells needing replacement.

Anyone done anything similar? Basically a rear hub motor in a 700C rim, not particularly massive power but a higher top end than most....

 

[Danidl]

Rode my little 36v, 350w, rwd, 700c on full charge today and I think I might have the answer. That's about the sort of performance I was hoping for so, my thoughts are, that, the same wheel/motor but with a 48v battery and controller should add enough to the top end to let me get towards as fast as I can reasonably pedal, while at the same time, not being an overly large motor/battery unit.

Would have to be confident the motor could cope with the added voltage though.

The motor is usually ok with the voltage..it is current which hurts them. It is the controller which is both current and voltage sensitive. You wanted to know how they work.. well it is sort of like this . A DC voltage is applied to the controller. It has typically 3 sets of transistor switches. The transistors are very beefy devices and can handle 20 to 60 amps .. depending on cost. These switch the current into three sets of coils creating a magnetic field. This pulls a toothed iron rotor towards a pole ,then that field is turned off and the next coil pulls it a bit further. This requires the coils to be energised in a very specific sequence and strict timing. The rotor is attached to reduction gearing to reduce speed and increase torque. The last gear is usually attached to the inside of the wheel hub. The coils are fixed to the axle nuts.. so what is unusual is that the housing rotates , rather than the shaft.
A larger diameter wheel will reduce torque, but increase road speed, so it's hill climbing ability is reduced.

 

[vfr400]

Back onto thinking about this recently as have acquired a yr old 48v battery with some cells needing replacement.

Anyone done anything similar? Basically a rear hub motor in a 700C rim, not particularly massive power but a higher top end than most....

It's pretty simple to get what you want: A 48v battery and controller will sort you out. A 15A controller should be enough. A 17A one will give you a bit more power to sustain a higher speed when you're tired at the cost of battery range. I's recommend a KT sine wave controller with LCD3 from PSWPower or Topbikekit. You can also find them on Ebay and Aliexpress.