Electrical Basics

A motor controller "is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults."

The controller sits between a battery pack and an electric motor, and it governs the amount of power sent to the motor. There is usually a throttle of some sort connected to the controller, the throttle is used by the operator to tell the controller what to do.

The Alltrax Document Depot contains some wiring diagrams of using an Alltrax controller in a vehicle. These are also somewhat applicable to other controllers, however details will differ.

A controller must be matched with the type of motor it is controlling because each motor type requires different power and control connections.

Electronic speed control: "An electronic speed control or ESC is a device mounted onboard an electrically powered radio control model in order to vary its drive motor's speed, its direction and even to act as a dynamic brake in certain controllers. An ESC can be a stand-alone unit which plugs into the receiver's throttle control channel or incorporated into the receiver itself, as is the case in most toy-grade R/C vehicles. Some R/C manufacturers that install proprietary hobby-grade electronics in their entry-level vehicles, vessels or aircraft use onboard electronics that combine the two on a single circuit board."

Controllers for Electric Motors: A Treatise on the Modern Industrial A book published in 1919 about electric motor controllers.

The Contactor: In electric vehicles a contactor serves to disconnect the battery pack from the rest of the vehicle. A contactor is a switch and turning the contactor on or off connects or disconnects the battery pack. A contactor can be manually operated, or by a relay. Contactors are part of the main power connections in an EV, and it must handle all the power used in the EV. As a switch it must open or close whenever the user desires, because it may be an emergency requiring the vehicle to shut down right away. This requires the contactor be rated for the power level in the EV, and it is known that the contacts in a contactor can be welded shut.

http://en.wikipedia.org/wiki/Contactor

Resistence: "The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current whichflows through it"

Electric Current: "Electric current is the rate of charge flow past a given point in an electric circuit, measured in Coulombs/second which is named Amperes."

Voltage: "Voltage is electric potential energy per unit charge, measured in joules per coulomb ( = volts). It is often referred to as "electric potential", which then must be distinguished from electric potential energy by noting that the "potential" is a "per-unit-charge" quantity."

Electric Field: "Electric field is defined as the electric force per unit charge. The direction of the field is taken to be the direction of the force it would exert on a positive test charge. The electric field is radially outward from a positive charge and radially in toward a negative point charge."

Batteries: "Batteries use a chemical reaction to do work on charge and produce a voltage between their output terminals. The basic element is called an electrochemical cell and makes use of an oxidation/reduction reaction. An electrochemical cell which produces an external current is called a voltaic cell. Voltages generated by such cells have historically been referred to as emf (electromotive force). "

Moving Coil Meters: "The design of a voltmeter, ammeter or ohmmeter begins with a current-sensitive element. Though most modern meters have solid state digital readouts, the physics is more readily demonstrated with a moving coil current detector called a galvanometer. "

Electromotive Force: "When a voltage is generated by a battery, or by the magnetic force according to Faraday's Law, this generated voltage has been traditionally called an "electromotive force" or emf. The emf represents energy per unit charge (voltage) which has been made available by the generating mechanism and is not a "force". The term emf is retained for historical reasons. It is useful to distinguish voltages which are generated from the voltage changes which occur in a circuit as a result of energy dissipation, e.g., in a resistor. "

Here's a few pages giving some basic electrical circuits and techniques which are basic to electric vehicle construction and maintenance.