My ongoing project is the mid-drive eCortina v3. With a new and improved motor, motor mounting system, and belt drive – the eCortina v3 encompasses the best of the previous machines.
The eCortina v3 electric bicycle is a more refined and reliable machine than my first electric bike build, of two years ago. It features a substantially larger motor and larger battery pack. Also as the weight of the battery pack and all other associated electronics are located in the triangle, the weight distribution and handling are far superior in the current build version.
This custom motorized bicycle, and other electric vehicle projects under development, use high performance motors (some RC and come hub), batteries, and controllers. The RC motors are lightweight brushless permanent magnet outrunners (magnets rotate outside stator coils) and modified hub motors used in hubs and as mid-drives.
The hybrid electric bicycle system is designed so that one can pedal only (human power), motor only (electric power), or in hybrid mode both motor and pedal at the same time. Under hybrid running the distance one can ride under one charge is extended. However, realistically the eCortina must be considered a motor bike with human assist.
The batteries are Lithium Polymer (LiPo) basically a Lithium ion chemistry variant or more typical Lithium batteries of various chemistries. LiPo’s batteries are sensitive to overcharging and over depletion, meaning that purpose built RC chargers and active, while in use, battery state monitoring, via a Cycle Analyst (not a BMS), are required to ensure good battery life. The more stable Lithium chemistries are used in my more advanced bike projects.
I am currently monitoring bike performance and range and will post results as they come in. The eCortina theoretically: 48v x 15Ah = 720Wh. LiPo batteries do not want to be discharged to less than 80% of total charge so: 720Wh x 0.8 = 576 Wh. If the bike uses 30Wh per mile: 576Wh/30Wh per mile = 19.2 motor only miles. The eCortina will go about 20 miles under mild riding with some pedaling at 20 mph.
The drive systems for the eCortina are derived from mostly bicycle related parts and concepts. There are two BMX style freewheels to allow pedaling without driving the motor and motoring without forcing the pedals to rotate. The BMX chains employed here are strong and up to the task of propelling this bike reliably.