The recent demand for more powerful and reliable Light Electric Vehicles has resulted in tremendous advancements throughout this industry over the last couple of years. While for the pedal bikes with electric assist currently the reduction of weight is the main priority, the electric scooters and motorcycle market is demanding more power on the road and increased range.
High torque is a paramount requirement especially for the electric motorcycles since they must keep with the acceleration and hill climbing of the regular fuel powered traffic.

Specific research and development for suitably powered electric bike motors have been undergoing for several years. It started with the prevailing 500W motors five years ago, then gradually the available power has been enhanced to 1000W, 1200W, 1500W with the aim to provide an experience that compares to the available gas powered motor scooters currently on the market.
Up to this point standard electro-magnetic laws applied in motors have fought over contradicting restraints since motor torque and speed fight against each other.

Hence thereof arrives the main problem for all electric motorcycles manufacturers: on one side they need a high starting and climbing torque, on the other they need a high speed of at least 60km/h. The easiest way to have a descent torque and high speed is to provide high electric current to the motor at start-up and during acceleration. Many manufacturers of electric motor bikes are designing their controllers to provide 80, 100 or even more amperes current to the motor. This causes several problems:
1. If the current drawn from the batteries exceeds 1.5c (1.5 times than the battery capacity), the life of the battery or more specifically the available number of charge cycles will be greatly reduced. This means that for 40AH battery the maximum current should not go beyond 60A.
2. When the motor is used on long hills high current can cause the motor to overheat which eventually degrades winding insulations to the point of premature failure. Brushed motors have additional problems. High current causes sparking between the contacts (between the commutator and the brushes) and unwanted ashes and abrasives are being deposited inside the motor.
3. High current also creates a bottleneck effect affecting the available voltage to the drive system. Very high current creates a voltage sag along the limited size power conductors which reduces the motor power especially on start and when going uphill. This explains in many cases why a an excessive needle drop of the voltmeter gage can be noticed when full throttle is applied on a 1500W motorcycle that consumes 80A for example.
Technically even a newer generation high efficiency 1500W brushless direct drive electric motor at its highest speed of 600rpm (45-50km/h) can produce only a torque of around 15Nm. This limits its climbing ability to around 6 degrees. Even if the motor controller set-up is optimized for slow start-up speed the controller must provide peak power that is much larger than the motor rated output power. Pumping in more current artificially increases the motor power and pushes the batteries, the motor and the controller beyond their sustainable limits and leads to premature failure. For example to reach a torque of 40-50NM with the 1500W rated brushless motor described above we need a peak power of 3000W. Since the motor is not designed for low speed, during start-up and when we go uphill its efficiency drops to 50-60% and this must be compensated with even higher current of 90-100A.

Providing a high current requires the use of high capacity heavy batteries and still in many cases a healthy current draw of 1-1.5c can not be achieved. To reduce or avoid high current detrimental impacts the manufacturers often either reduce the performance of the electric motorcycles or provide the motor with a thermo-mechanical overload protection which often reduces the reliability and availability of the vehicle. To reduce the harmful effect of the high current some manufacturers are providing dual speed motorcycle based on high and low current limits. This however only restricts the current provided to the motor and reduces its performance especially on hills. Obviously, the big current is one of the most limiting factors which impact the stability and growth of the e-vehicle industry.
Greenwit Technologies' newly designed electric driving system for the MOTORINO™ line of motorcycles eliminates most of the problems related to high powered brushless electric motors. It is based on a proven and very efficient concept. We have been able to effectively integrate in one housing an optimized high and a low speed brushless motor and combined it with a matching intelligent dual controller. The motor controller pairs are selected depending on driving conditions. An electronic automatic gear shifter commanded by a speed sensor automatically shifts between the two motor modes. In this way a high torque of 90Nm with a speed of 30km/h and 20Nm with a speed of 60km/hr can be achieved. In both high speed/high torque modes the maximum current is 45A. The efficiency is 87-90% in the two “motors” since each “motor” is coupled with a customized controller drive circuit and there is no need to overpower a motor designed for high speed for high torque performance. This concept also allows the use of lower capacity batteries of 38AH or less, reducing the weight of the bike which further adds to the overall efficiency. This high efficiency design makes it possible to achieve significantly longer ranges when compared with current brushed or brushless single speed systems.

GREENWIT TECHNOLOGIES Inc is currently developing 3 and 4kW high efficiency brushless motors specifically designed for converting larger engine gasoline motorcycles (125cc and up) into electric. They are expected to be available in spring 2007.