Troubleshooting -Electric Drive System

Drive System Major Components

Troubleshooting the electric drive system is a process of elimination. There are four major components to the electric drive system:

  • Battery Pack  (and associated battery charger)
  • Motor Controller
  • Motor
  • LCD Display (Cycle Analyst V3.0 Electric Vehicle Management System)


Drive System Operational Overview

Builder's Note: To better understand what may not be working correctly, it's important to have a fundamental understanding of how the electric drive system functions. Take a moment to review this information as it will help you better understand the troubleshooting process we'll take. 
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⚠️ The cables shown between the various components in these diagrams are representative of cable assemblies, representing multiple wires/conductors between the components. For more detailed wiring information, please refer to the schematic diagrams.

Battery Pack

Click to enlarge: Battery Pack shown disconnected from Motor Controller

The battery is the most essential component of the electric bike system. Without power, nothing happens.

The powerful lithium ion battery pack on your Fat Woody cruiser is rated at +50vdc. When it's fully charged, it puts out around +58vdc. As you ride your bike, that voltage will continue to drop. To protect the battery from too deep a discharge, there is a programmable 'low voltage cut-off' or LVC threshold of around 48v, where the CA computer management system start to shut down power output.

Note: Over the life of the battery (600-700 charge cycles), this voltage (+58v) will continue to slowly drop. This is normal.


Motor Controller

Clink to enlarge: Electric gateway closed when no throttle is applied.

The motor controller is the electric gateway component between the battery pack and the motor. Without it, the motor would spin at full speed until the battery ran out of power.

The motor controller is appropriately designed to operate within the voltage range of the battery pack, as well as operate with the limits of its current capability. The Fat Woody motor controller is rated to 60v @ 40 amps.

Once the 50v battery is plugged into the motor controller, the motor controller provides a small amount of that battery power (+5vdc) to operate the Cycle Analyst computer.


Electric Motor

Click to enlarge: Applying throttle opens electric gateway to motor hub.

The electric motor is not really an intelligent device, but rather just spins when voltage is applied to it. The more current (amps) fed to it, the faster it will spin. Conversely, the less current you feed to it, the slower it spins.


The thumb throttle tells the motor controller how much electric current you want to send to the motor. In the case of the Fat Woody cruiser, the throttle tells the Cycle Analyst computer, and the CA relays the information to the motor controller. This allows the CA computer to impose preset programmable limits relating to power and speed.


Cycle Analyst Computer/LCD Display

Click to enlarge: E-bike power output is ultimately controlled by the CA.

If the CA computer is programmed to limit the power output of your e-bike, the throttle output signal it sends to the motor controller will be less and subsequently, the electric motor will spin slower. You can adjust these preset limits in the Cycle Analyst set-up menu.

Additionally, the Cycle Analyst employs a temperature sensor in the electric motor. If the motor hub begins to overheat, the computer will automatically rollback the amount of throttle applied to the motor controller until the temperature comes down.


Brake Lever:  Throttle Inhibitor

Click to enlarge: When brakes are applied, all power to motor shuts down.

For safety reasons, your brake levers have been directly connected to the motor controller for the purpose of over-riding any throttle input, essentially inhibiting any power flow to the motor hub.

For this reason we'll disconnect it, as it is the first thing to rule-out when troubleshooting electric drive issues.






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