Balancing the System

The key to getting the most out of your drive system is balance.  Here’s what I mean.

You have three basic events in an electric drive: discharge, modulation, and conversion.  That is, your batteries discharge the current.  The controller and throttle modulate the current going to the motor.  The motor converts the current to force.  The only secret is that you need to match up what controls these three events, and you get a balanced system.

Here’s a little sheet showing three basic balanced systems- a low, medium and high-power system.

Typical System Specs
Discharge (Battery “C” Rating) Modualtion (Controller Power Rating) Conversion (Motor Rating)
e-Bike 2C 100 amps 250 watts
Scooter 4C 250 amps 500 watts
Motorcycle 10C 450 amps 10 KW
Race Motorcycle 40C 800 amps 50 KW

…and here’s an idea of what happens when you have bottlenecks:

Bottlenecks and Failure
Ratings Too High Too Low Just Right
Battery discarge Batteries do not provide all the current they are able to. Batteries are stressed, possibly damaged by overloading Batteries remain within operating tolerances for long life, provide maximum safe current
Modulation Controller/circuit is larger, heavier and more expensive than necessary Contoller becomes bottleneck by not providing available current through to the motor.  Overheating and damage to controller or circuit likely. Controller stays within safe operating ranges and delivers full avaialbe current to the motor.
Motor Rating Motor is too large and heavy for the application Motor will overheat and fail Motor runs at about 90% of it’s capacity, stays within safe operating temperatures, and is able to handle the total available current.
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