Overview

The general idea of charger is to poll if the charger is plugged in, then request permission from centre console to charge and start charging if allowed. When the battery is full or the charger is unplugged, we stop charging.

Modules:

• charger_controller: This module is effectively a wrapper around mcp2515 that manages communication explicitly with the charger. It can be thought of as the ‘driver’ for the charger.

  • uses mcp2515’s driver to send charging messages

    • methods:

      • charger_controller_init

      • charger_controller_activate

      • charger_controller_deactivate

    • Upon receiving a message from the charger, checks for fault bits in the status, and sends a CHARGER_FAULT message with the appropriate fault.

• charger_control_pilot: wraps PWM, also converts PWM value to current based on J1772 standard.

  • Exposes uint16_t control_pilot_get_current() to read the PWM of the control pilot pin. Returns a value in deciamps that is the maximum current the charger can provide.

• charger_connection_sense: periodically reads the state of the connection_sense pin to determine whether or not the charger is connected. The charger can be unplugged, plugged in with the button pressed, or plugged in with the button released. You need to press the button to unplug the charger (think of it like the handle on a car door - the door can be open, closed with handle pulled, or closed with handle not pulled).

  • periodically poll the connection sense (CS) pin via ADC to determine state (defined at 500 ms)

  • upon connecting or disconnecting, transmit SYSTEM_CAN_MESSAGE_CHARGER_CONNECTED_STATE with the appropriate exported enum value, and raise a CHARGER_CHARGE_EVENT_STOP/BEGIN if it’s disconnected or connected respectively.

• begin_sequence: handles the sequence of things that need to happen to begin charging

  • upon processing a CHARGER_CHARGE_EVENT_BEGIN event, transmit SYSTEM_CAN_MESSAGE_REQUEST_TO_CHARGE.

    • Centre console will get the request. If we’re in the appropriate drive state (parking) centre console will send back SYSTEM_CAN_MESSAGE_ALLOW_CHARGING.

  • Upon receiving a SYSTEM_CAN_MESSAGE_ALLOW_CHARGING, begin the init sequence:

    • make sure charger is on (transmit SYSTEM_CAN_MESSAGE_CHARGER_FAULTif not)

    • Get a pwm reading from control pilot to deduce max current allowed

    • set relay state then load switch state

    • enable charging via control pilot

    • activate charger via charger_controller_activate

• stop_sequence: handles the sequence of things that need to happen to stop charging

  • Upon processing a CHARGER_CHARGE_EVENT_STOP, the sequence will:

    • deactivate the charger via charger_controller_deactivate

    • Turn off the control pilot

    • Turn off the load switch then the relay

• battery_monitor: stops charging when the battery is full.

  • repeatedly receives SYSTEM_CAN_MESSAGE_BATTERY_AGGREGATE_VC

  • If voltage is over 135 V (defined threshold) will raise a CHARGER_CHARGE_EVENT_STOP event.

Operation Mode:

1. The BMS sends operating information (Message 1) to charger at fixed interval of 1s. After receiving the message, the charger will work under the Voltage and Current in Message. If the Message is not received within 5s, it will enter into communication error state and stop charging.

CAN Communication

• Speed: 250Kbps

Open

Addresses

Open

Messages

Message 1:

This is the message we send to the charger.

Sender: 0xF4 → BMS

Receiver: 0xE5 → Charger Control System

Rest of the Message: 0x1806

• Priority: 6

• R: 0

• DP: 0 (fixed)

• PF: 6

Message 2

This is the status message charger sends to us.

Sender: 0xE5 CCS

Receiver: 0x50

CAN Communication

MCP2515 is responsible for sending and receiving CAN messages.

SAE J1772 Standard Notes

J1772 Plug Pinout

Control Pilot PWM

Circuit:

Proximity Pin (PP) or Proximity Detection

page 18 of standard:

Proximity Sense:

GPIO Address: PA7

Design Options:

• periodic ADC running always

• periodic ADC only activated when the charger is powered (PB1)

Charging Operation:

• car should be in park not neutral

  • we can either be in a undervoltage state, or neutral

• we’re also charging from solar

• need to have a threshold for opening the solar relays

• that threshold is not necessarily the overvoltage fault

  • cells are 95% charged

• whenever solar closed, battery has to be closed

• we should always make sure

• motor controllers must not be connected

• when car’s in parking, mci should disconnect

  • unless we’re not in an “undervoltage charge state” and we’re in “park” we should be able to charge

  • there needs to be continuous communication between BMS and the charger to taper the charging.

  • for MVP we keep it simple “two states”

• once charging done:

  • tell evse by setting the switch

  • tell charger to stop

  • open the relay

• shouldn’t go to neutral or drive again, unless we pull out the charger

After charging:

• bms needs to send a taper message

• bms needs to send a fully charged message

• talk to liam

Richard’s Notes

Notes on Charger CAN Comm:

Receiving Data:

·      Every second from BMS with CAN ID 1806E5F4

·      8 bytes of Voltage and Current requested

·      If no valid CAN message, charger stops charging until valid CAN message received

Sending Data:

·      Sends CAN message every second with Voltage, Current, and status information

·      Source Address - BMS – 2244(0xF4)

Stats & Errors:

·      Sends 2 messages, one to BMS and one to CCS

·      Output Voltage and Current (2 Bytes each)

·      Status Flags (Byte 5) 

Pre-Charging Safety Requirements:

·      All Status Flags are 0

·      Received valid CAN message from BMS (or CCS) 5 seconds or earlier

Controlled Relays & Hardware