English: Drawing corrections (to be done)

• Missing junction dot, Negative contactor negative to chassies ground
• Run latch and collision sense to be moved to a separate drawing, inputs to this drawing will be safe igniton (top contactor) and run (bottom contactor)
• Add chassies ground symbol
• Isolate relay contacts with 5 amp fuses, using AWG 16 to feed
• Rework switch and relay setup for better isolation of DC and AC sides, use more commonly available components.
• <add notes here>

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.

Not shown on this drawing: pack power routing to vehicle service voltage converter, heater, and instrumentation (shunt, ammeter and voltmeter).

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 include heater relay, brake vacuum controls, 12 volt converter, and other pack voltage auxiliaries such as air conditioning and power steering pump motor if provided
• 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 AC power input via Run/Charge switch. This should be an industrial grade contactor with appropriate ratings for coil voltage (110 or 220V AC) and contact current (20, 30 , or more amperes depending upon charger requirements). If a single pole contactor is used it is placed in the hot lead (H). 220 volt systems require at least two poles in this AC contactor, breaking both hot leads (red and black).
• 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

  SI: Safe Ignition, vehicle ignition power controlled by inertial switch (I-S), and run-charge switch (SW1). Opening of the inertial switch will cause all low voltage relays elsewhere to open as well as causing the power contactors to open, removing pack voltage from all subsystems

• 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). This does not carry high currents but must be capable of withstanding the AC voltage used as input to the charger. A good quality toggle switch is recommended, with appropriate dampness ratings for its intended location. This switch should be located near the connection point for AC power and not at the driver's controls (in order to allow time for proper pre-charge), unless a pre-charge detection circuit is included.

Run-charge switch (SW1) notes:

• The logic of this circuit can be implemented with various combinations of relays and switches. By using an appropriate latching circuit and push buttons the circuit can ensure that the charger will be off when plugged in (most modern EV chargers implement a "soft start" that makes this unnecessary for prevention of plug damage).
• 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
• A good quality 4PDT toggle switch may be difficult to find. A four pole double throw (4PDT) light duty relay (5 amp contacts) controlled by single pole switch closure providing AC power, or 3PDT AC and a DPDT switch controlling AC power to the relay and ignition disable may be substituted for this switch but must maintain the cascaded operation of Ry2, required since isolation must be performed before power is applied to the charger, regardless of the time constants of the relays.

For a charger whose AC power is controlled externally, for example, one that uses an Avcon conductive paddle, the AC power should be used to control a 3PDT relay of appropriate power rating. In this case two of the contacts are used to break the motor controller pre-charge using normally closed contacts, while the third provides AC power to the charger with a normally open contact (for light duty charger, 25 Amperes AC or lower), or to a power contactor (for higher power chargers),

Wire sizes:

Charger current wires to F2, F3, F4, and charger AWG 10 typical. If controller pre-charge is performed via AWG 16 wires then 5 amp fuses should be provided at any end that is connected directly to pack voltage.

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

Relay coil wires AWG 16 or 18 typical

Cautions:

• 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 (normal run and shut-down without recharge) should use a sense or timer circuit to prevent operation until the pre-charge is complete. Systems sensing pack voltage relative to pre-charge voltage should use optical isolation methods to protect low voltage circuits.
• 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.