Just a thought

[Linfitter]

Garage Compressors one of which I have got have got to be able to start when the pressure in the air tank drops below a set level. This means that a standard electric motor unless of a large size would not be up to overcoming the initial force needed to kick-start the compressor process. This problem has been got around by the use of an extra circuit and a ‘thrower’ switch. When the motor is stopped both circuits kick in and the motor has enough power to turn the Compressor. When the Compressor is up to speed the thrower switch breaks the auxiliary circuit and the motor runs on at its nominal power.

I am wondering if something like this system could be used on a hub ebike motor with the use of a small auxiliary battery to give the extra power needed like when climbing really steep hills.

Seems to me to be a simple solution to getting extra power when needed and yet still keeping within the Law as the nominal motor rating would be unaltered or so I would think.

Any comments.

Yours sincerely

Linfitter.

 

[eddieo]

OMG! he has cracked it!.... Perpetual motion!

 

[Jeremy]

No need to go to the trouble of doing this.

Assuming that you want to stick to the EU limits (to which the law here are currently turning a blind eye), rather than the very much more restrictive UK legal limit, then all that's needed is to ramp the throttle/pedelec acceleration curve, which is what a fair few manufacturers now seem to be doing. This allows several hundred watt motor to be rated as "250W". Typically, a newer EU approved ebike might have a 500W motor in reality, yet be rated at "250W" as far as the regulations go. Seems a very sensible approach, to me.

Alternatively, you can easily inverse ramp the current limit in the controller, so that more torque is delivered at low speed, less at high speed. This would allow a hub motor to deliver more torque at low speed, whilst still staying within a nominal power limit.