What motors do you use? 

Krys electric bicycle motors are brushless, running on 24volt or 36volts DC.  Krys Scooters use 60V brushless systems for increased pulling power up hills and starting from traffic lights, especially with 2 people on board.

In brushless motors, the current is pulsed electronically rather than having brushes that need to be periodically replaced.  Generally speaking, for electric bikes, brushless motors are a better option.

Brushless motors can have gears or direct drive.  

- Geared motors normally provide higher low speed torque important for pulling away from traffic lights and junctions.  

- Direct drive motors don't normally have gears, instead relying on their larger size to provide the extra power.  

Generally, geared motors are preferable for normal electric bikes.  Larger and faster travelling moped style scooters normally use gearless direct drive motors - at slow speeds they put a higher load on the battery, but once at speed are more efficent and quieter than geared motors; they have no added friction from gears running at high speed.

Geared motors make a quiet whir when operating.  This is desirable so pedestrians can possibly hear the bike coming before they step out onto the road.