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Contactor pre-charge and charge disconnect. See caution and disclamer at bottom of document

This circuit is for use with transformerless chargers using grounded extension cord from a GFCI (Ground Fault Controlled Interrupt) protected outlet.

Key to drawing:

• AC: Alternating current plug connection to extension cord for battery charging
• B: Battery
• C: indicates "charge" position of run-charge switch
• C1, C2: Contactors, at least one located near pack
• Chg: Charger
• Cr: Motor controller
• F1: High current pack fuse or circuit breaker (several hundred amperes typical)
• F2, F3: Battery charger fuse at contactor - 20 to 30 amps typical, fuses located where wire size changes at contactor
• F4: Controller pre-charge fuse - 5 amps sufficient. Note that wire is sized appropriate to F2, so F4 can be same rating as F2 (20 to 30 amps)
• F5: Charge relay 110 volt AC fuse - 5 amps sufficient
• G: AC ground, green wire in U.S. installations
• Gnd: Vehicle chassies ground
• H: AC hot. black wire in U.S. installations, 220 volt US installations will also provide an additional wire, red and hot of opposing phase
• I-S: Inertial switch. If R1 is run-latch relay then this inertial switch will also disable all relay controlled circuits attached to run circuit. These should include heater, brake vacuum, 12 volt converter, and other auxiliaries such as air conditioning and power steering pump motor.
• Ign: Ignition circuit, controlled by key switch
• N: AC neutral wire, white in U.S. installations
• R: indicates "run" position of run-charge switch
• Ry1: Run relay or run switch. Relay shown wired for run latch initiated by Start position on operator keyswitch (not shown)
• Ry2: Charge relay powered by AC from power input via Run/Charge switch.
• RC: Controller pre-charge resistor (varies with application, see controller documentation, 750A 25W typical)
• RL: Run latch provides power to run latch circuit to keep Start/Run active after start.
• SR: Start/Run, 12VDC applied when in run mode. May be wired as a latching relay engaged by the start keyswitch function. C2 operating circuit may also be interrupted by the throttle switch.
• SW1: When not charging this completes the controller pre-charge via closed contacts (1) and (2) and completes the Safe Ignition path from the intertial switch (I-S) to Relay One (Ry1).

Run charge switch notes:

• Charge switch should be connected where charging cord is connected to vehicle. Not placing this in cab will give more time for controller to pre-charge.
• Charge cord physical access door is separately interlocked to prevent run - see run latch circuit (to be provided)
• (1) Connects controller charge priming resistor to positive side of pack
• (2) Completes controller charge prime circuit to negative side of pack
• (3) Activates high current AC relay to power charger
• (4) Ignition safety - system cannot be run while switch is in charge position

Wire sizes:

Charger current wires to F2, F3, F4, and charger AWG 10 typical.

AC charger wires AWG 10 typical

Main battery wires AWG 2/0 to 4/0 typical

Relay coil wires AWG 16 or 18 typical

Caution: This assumes permanent connection of the pre-charge resistor and that a sufficient interval between charging AC disconnect and system operation will allow the pre-charge resistor to fully charge the controller capacitors. Failure to allow sufficient pre-charge may damage the contactors, even welding them in the closed position. Systems providing a complete system shut-down between run conditions should use a sense or timer circuit to prevent operation until the pre-charge is complete.

A mechanical charging door interlock should also prevent vehicle operation while plugged in.

Drawing by User:Leonard G. Use subject to Disclaimers: Responsibility for accuracy and liabilities for application is by the user of this document, not the author, checkers, or modifiers.