Electric Vehicle Conversion Help

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Wiring Diagrams

Isolated Systems

The figure above is a simplified diagram that illustrates how the electrical systems in an electric vehicle are isolated from each other. There are two main isolated systems:

1. 12-V automobile electrical system

2. High-voltage system based on the battery bank

Each system has its own battery charger.

The figure below shows an alternative method of charging the 12-V battery using a power converter/charger that operates from the high-voltage battery bank. In this case, the battery charges as needed from the high-voltage bank during use. Although not shown in the diagram, it's a good idea to place a relay on the high-V side of the converter and another one on the 14-V side of the converter - each relay has a 12-V coil and are activated by the key switched 12 V. These relays prevent the converter from drawing current from the HV bank when the vehicle is off and also prevents the converter from drawing a small current from the 12-V battery when the vehicle is off.

Motor Wiring Options

The series-wound motor allows many wiring options that produce the same direction of rotation. Series motors are also called Universal Motors because they will actually run on AC or DC. If you reverse the applied polarity to the motor, it continues in the same direction. Changing the polarity of both the armature and the stator at the same time causes the motor to continue in the same direction. The only way to reverse a series-wound motor is to change the polarity of either the armature or the stator, but not both. This is why a reversing contactor is used to change the polarity of the stator winding to create bi-directional operation. Note that this is not necessary when a standard transmission is used because it has a reverse gear.

Did you know that 120 VAC electric drills, saber saws, reciprocating saws and circular saws all have universal motors and will run directly from your 96 to 120 V battery bank? It's true, and so will all 120 VAC incandescent light bulbs.

System Control

The system control circuit, in the green box, is an interface control and safety circuit between the two systems. The control circuit contains relays that energize according to operational rules.

Rules:

1. The high-voltage motor and control system must not energize if the parking brake is on.

2. The high-voltage motor and control system must not energize if the operator has his/her foot on the gas pedal.

3. The high-voltage motor and control system must not energize until the gas-pedal foot (right foot) is on the brake pedal.

If the control circuit is designed to follow these rules, safe operation can be ensured. The following wiring diagram shows the control circuit that I designed for my Chevy S10 conversion:

Note: The following control circuit diagram is for the Curtis 1209, 1221 and 1231 controller or any controller that requires the high-voltage connection from terminal 7 of the control box (blue line).

The photo below relates the PB6 micro switch connections to the diagram above.

The small black box is the control box that contains the circuit just above.

The gray box, with diamond-plate cover, contains the heavy-duty contactor and fuses (F).

Note that the above control circuit is actually safer than what is shown in the Curtis Instruments controller manual (1209B/1221B/1221C/1231C Manual). Curtis recommends that a pre-charge resistor be placed across the heavy-duty contactor terminals. If this is done, high-voltage from the battery bank will be present at all terminals of the motor and controller even when the key is off. The user would be required to remember to turn off the main circuit breaker before working on the motor and controller system, which of course is a good practice anyway. The modified circuit above helps you avoid unnecessary shock if you forget.

Disclaimer: Neither EVhelp, LLC nor Mark E. Hazen is responsible for injury or losses of any kind resulting from use or misuse of information contained herein.