Loading
Notes
Study Reminders
Support
Text Version

Vehicle Subsystems - Lesson Summary

Set your study reminders

We will email you at these times to remind you to study.
  • Monday

    -

    7am

    +

    Tuesday

    -

    7am

    +

    Wednesday

    -

    7am

    +

    Thursday

    -

    7am

    +

    Friday

    -

    7am

    +

    Saturday

    -

    7am

    +

    Sunday

    -

    7am

    +

Leaving aside the vehicle body, tires, suspension system, doors and windows, wipers, mirrors, and interiors, we can define the electrical vehicle's subsystems as The Drive-Train, The Battery, DC to DC Converters, and Auxiliary and Control Unit.

An electric vehicle's Drive-Train includes motors, controllers, batteries, and gears. They are the elements that drive the performance of the vehicle. The performance of the vehicle is characterized by Vehicle Torque, Speed and Power.

The vehicle's peak power, when the vehicle performs at maximum efficiency for a short period of time, usually 10 to 20 seconds, and the vehicle's continuous (nominal) power, need to be in thermal equilibrium, to avoid the motor from overheating and failing.

Gears in all vehicles are used to multiply torque, and thus multiply power. Unlike Internal Combustion Vehicles, which need multiple gears and a changeable gear-box, Electric Vehicles are usually designed to work efficiently with a large range of speeds and torques. Therefore, electric vehicles only need a single fixed gear.

Batteries in electric vehicles are designed to provide Energy over a range, or period of time over distance, operating at nominal and peak capacity. This Battery Energy or Capacity is expressed in Kilo-Watt hours.

kWh=V*Ah/1000 (nominal voltage * Ampere-hour/1000)

To guarantee long battery life and extend battery charge and discharge cycles, the battery should never be fully emptied or fully charged. The design of the vehicle will have 5 to 7 percent thresholds both at the bottom and top of the battery to avoid the battery from fully draining, or being completely full. Therefore, the battery’s Usable Energy, or each charge and discharge cycle, is typically only 85% of the battery’s total capacity, typically expressed as x%. This usable energy is also known as Depth of Discharge.
As the battery wears down, Battery Capacity is reduced with each charge-discharge cycle. When Battery Capacity remaining is y% (typically 80%) of the initial capacity, the range gets proportionately reduced and the battery life for the electric vehicle is over and needs replacement.

End of Life Cycle is expressed as Usable Energy = x*y*C