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TC_Charger -- Open Source EV Charger Controller

An ESP32-S3 based controller for the HK-LF-115-58 6.6kW On-Board Charger (OBC) by TC Charger Standard. This project provides full CAN bus control, monitoring, and telemetry for charging lithium battery packs from 20V to 108V.

Originally designed for a 20S (84V) electric scooter build, but configurable for any pack voltage within the charger's range.

License

CC BY-NC-SA 4.0 -- Free for personal and open-source use. Commercial use requires a separate license. See LICENSE for full terms.

All contributions must be open source. If you want commercial rights, contact the project owner and contribute your improvements back.

Hardware

Charger

Item Detail
Model HK-LF-115-58
Configuration 9000/HD623
Manufacturer TC Charger Standard
Power 6.6 kW
Output 20V - 108V, up to 60A
CAN bus 250 kbps, CAN 2.0B extended 29-bit frames (SAE J1939 style addressing)
Charging method Pulse charging (CC-CV with pulsed current delivery)

Controller (Main Brain)

Item Detail
MCU ESP32-S3 DevKitC-1 N16R8
Flash 16 MB
PSRAM 8 MB OPI
Framework Arduino (single .ino sketch for Arduino IDE)
Upload COM3 @ 921600 baud
Monitor 115200 baud (Putty or any serial terminal)

CAN Transceiver

Item Detail
Chip SN65HVD230 (WCMCU-230) or CJMCU-1051 (TJA1051)
Voltage 3.3V only -- both transceivers work at 3.3V. Do NOT power at 5V (will damage ESP32 GPIO)
TX GPIO 4
RX GPIO 5
S pin Must be tied to GND for normal operation
Termination 120 ohm across CANH/CANL at each bus end

Daughter Board (Temp Node) -- Optional

Item Detail
MCU ESP32-C3 Super Mini
Purpose 5x NTC thermistor array + AHT20/BMP280 environment sensor
Communication RS485 Modbus to Main Brain (GPIO 17/18)
NTC sensors 100K 3950 beta, channels 0-4 (GPIO 0-4 on C3)

Additional Peripherals (Main Brain)

Peripheral Interface Pins
SH1106 OLED 128x64 I2C SDA=GPIO8, SCL=GPIO9, addr 0x3C
AHT20 temp/humidity I2C addr 0x38 (shared bus)
BMP280 pressure I2C addr 0x76 or 0x77 (shared bus)
QMC5883L compass I2C addr 0x0D (shared bus)
HGLRC M100 GPS UART2 RX=GPIO15, TX=GPIO16 @ 115200
WS2812B RGB LED Data GPIO48 (onboard)
NEXT button Digital GPIO6 (active LOW, internal pullup)
HOLD button Digital GPIO7 (active LOW, internal pullup)

CAN Protocol

Frame 1: Controller to Charger (TX)

  • ID: 0x1806E5F4 (extended 29-bit)
  • Interval: 1000 ms heartbeat (charger disables if no frame for 5 seconds)
  • Byte order: Big-endian (Motorola)
Byte Field Encoding
0-1 Max charge voltage 0.1 V/bit (e.g. 840 = 84.0V)
2-3 Max charge current 0.1 A/bit (e.g. 200 = 20.0A)
4 Control 0x00=charge, 0x01=disable, 0x02=sleep
5 Mode 0x00=charging, 0x01=heating
6-7 Reserved 0x00

Frame 2: Charger to Controller (RX)

  • ID: 0x18FF50E5 (extended 29-bit)
  • Interval: 1000 ms
Byte Field Encoding
0-1 Output voltage 0.1 V/bit
2-3 Output current 0.1 A/bit
4 Fault flags See below
5 Status flags See below
6 Connector flags See below
7 Temperature raw - 40 = degrees C

Fault Flags (Byte 4)

Bit Field
0 Hardware fault
1 Temperature fault
2-3 Input voltage (0=OK, 1=under, 2=over, 3=none)
4 Output under-voltage
5 Output over-voltage
6 Output over-current
7 Output short circuit

Status Flags (Byte 5)

Bit Field
0 Communication timeout
1-2 Working status (0=init, 1=working, 2=stopped, 3=standby)
3 Initialization complete
4 Fan on
5 Cooling pump on

Serial Commands

All commands are single keystrokes (no Enter needed). Works via USB serial (Putty/Arduino Serial Monitor at 115200 baud) and also via BLE and WiFi.

Key Command Description
r Resume Start charging at current voltage/current setpoints
s Stop Disable output, charger stays awake on CAN
e End Charger enters sleep mode. Wake with w then r
w Wake Send CAN handshake frame after power-on or sleep
+ Current +1A Increase charge current (max 60A)
- Current -1A Decrease charge current (min 0A)
v Voltage +0.5V Increase target voltage (max 108V)
V Voltage -0.5V Decrease target voltage (min 20V)
b Buddy Mode Charge another battery -- stops output, unlocks full voltage range
n Normal Mode Exit buddy mode, restore home settings (84V/2A)
0 Reset Energy Reset session and previous counters (lifetime preserved)
p Print Status Full report: setpoints, charger output, energy, range estimates
? Help Show command list

Boot Defaults

  • Voltage: 84.0V (20S x 4.20V)
  • Current: 2.0A (safe starting level)
  • State: DISABLED (nothing happens until you type r)

Energy Tracking

Three tiers of energy measurement, plus separate buddy tracking:

Tier Scope Persistence
Session Current charge event (Wh, Ah, duration, miles added) RAM -- resets on new session
Previous Last completed charge session RAM -- overwritten each time
Lifetime Total energy ever charged NVS flash -- survives reboots
Buddy External battery charge only RAM -- resets when exiting buddy mode

Energy is calculated from EMA-smoothed voltage and current values, which accurately handles the charger's pulse charging behavior.

Range Estimation

  • Default efficiency: 32 Wh/mile (adjustable)
  • Status report (p) shows charge time needed for +5, +10, +20 miles at current rate
  • Every status line shows miles added this session

Remote Control

BLE (Bluetooth Low Energy)

  • Device name: ScooterCharger
  • Service UUID: 4fafc201-1fb5-459e-8fcc-c5c9c331914b
  • Command characteristic (...26b0): Write single-char commands (r, s, e, w, +, -, v, V, b, n, 0, p, ?)
  • Charger telemetry (...26b1): 22-byte binary, notified at 1 Hz

Telemetry format (little-endian):

Offset Size Field
0 2 Smoothed voltage (dV, uint16)
2 2 Smoothed current (dA, uint16)
4 4 Session Wh (float)
8 4 Lifetime Wh (float)
12 1 Charging (0/1)
13 1 Buddy mode (0/1)
14 4 Power watts (float)
18 4 Miles added (float)

WiFi (Fallback)

  • AP SSID: ScooterCharger
  • Password: charge84v
  • Status: http://192.168.4.1/status (JSON)
  • Commands: http://192.168.4.1/cmd?c=r (any single-char command)

WiFi runs as a soft AP simultaneously with BLE. Use BLE when signal is strong, fall back to WiFi when needed.

OLED Display

7 pages on the SH1106 128x64 OLED, auto-advancing every 8 seconds:

Page Title Content
1/7 Charger Output Pack voltage, set voltage, current, power, faults
2/7 Ambient Sensors Main board + daughter board temp/humidity/pressure
3/7 Battery NTC Temps 5x NTC thermistor readings (Fahrenheit)
4/7 Pack Status BMS voltage, current, SOC, Ah, charge/discharge flags
5/7 Pack Health MOS temp, battery temps, SOH, cycles, runtime
6/7 20S Cell Volts All 20 cell voltages in 5x4 grid + min/max/delta
7/7 GPS & Range Lat/lon, speed (mph), range (miles), compass, satellites

NEXT button (GPIO 6) advances pages. HOLD button (GPIO 7) freezes on current page.

RGB LED Status

The onboard WS2812B LED (GPIO 48) indicates system state:

Color Pattern Meaning
Blue Slow blink Idle, charger not active
Green Solid Charging
Red Fast blink Overtemp or fault
Cyan Blink Undertemp (below freezing)
Orange Blink BMS fault
Yellow Blink Communication timeout
White Fast blink Booting

Pulse Charging Behavior

The HK-LF-115-58 uses pulse charging. CAN status frames report instantaneous snapshots, which bounce wildly between 0A and 30+ A even when the average is 12A. The firmware uses exponential moving average (EMA) smoothing with alpha=0.1 to display the true average values.

All energy calculations use smoothed values, which accurately reflect total energy delivered regardless of pulse vs. steady delivery.

Hardware Requirements

Minimum ESP32-S3 Board Specs

Requirement Minimum This Project Uses
MCU ESP32-S3 ESP32-S3 DevKitC-1
Flash 16 MB N16R8 (16MB Flash / 8MB PSRAM)
PSRAM 8 MB OPI N16R8
USB USB-to-UART bridge (CP2102/CH340) DevKitC-1 has both native USB + UART bridge

Important: Boards with only 4MB flash (like the basic ESP32-S3-WROOM-1 N4) will NOT work. The compiled firmware is ~1.3MB and requires a 3MB APP partition which needs 16MB flash. Verify your board's flash size before purchasing.

Common compatible boards:

  • ESP32-S3 DevKitC-1 N16R8 (recommended, this is what we use)
  • ESP32-S3 DevKitC-1 N8R8 (8MB flash -- will work with smaller partition but tight)
  • Any ESP32-S3 board with 16MB+ flash and exposed GPIO 4, 5, 6, 7, 8, 9, 15, 16, 17, 18, 48

Arduino IDE Setup

Follow these steps exactly. Incorrect settings will cause boot loops, blank serial output, or flash errors.

Step 1: Install ESP32 Board Package

  1. Open Arduino IDE
  2. Go to File > Preferences
  3. In "Additional Board Manager URLs" add: 
    https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
  4. Go to Tools > Board > Boards Manager
  5. Search for "esp32" and install "esp32 by Espressif Systems"

Step 2: Board Settings (Tools Menu)

Set each of these in the Tools menu. Every setting matters.

Setting Value Why
Board ESP32S3 Dev Module Matches our MCU
Flash Size 16MB (128Mb) Must match your board's physical flash. Using 4MB on a 16MB board causes boot loops with "partition table error"
Partition Scheme 16M Flash (3MB APP/9.9MB FATFS) Firmware is ~1.3MB, default 1.2MB partition is too small. This gives 3MB for the app
PSRAM OPI N16R8 uses OPI PSRAM. Wrong setting = crash or no PSRAM
USB CDC On Boot Disabled Critical. If "Enabled", Serial output goes to native USB instead of UART bridge (COM3). You'll see nothing in Putty/Serial Monitor.
Upload Speed 921600 Fastest reliable speed
USB Mode Hardware CDC and JTAG Default, leave as-is
Port COM3 (or your board's port) Check Device Manager if unsure

Step 3: Install Libraries

Go to Sketch > Include Library > Manage Libraries and install:

Library Search Term Author Purpose
FastLED FastLED Daniel Garcia WS2812B RGB status LED
U8g2 U8g2 oliver SH1106 OLED display
Adafruit AHTX0 Adafruit AHTX0 Adafruit AHT20 temp/humidity sensor
Adafruit BMP280 Library Adafruit BMP280 Adafruit BMP280 barometric pressure
TinyGPSPlus TinyGPSPlus Mikal Hart GPS NMEA parsing
PubSubClient PubSubClient Nick O'Leary MQTT for Home Assistant

Accept any dependency prompts (Adafruit BusIO, Adafruit Unified Sensor, etc.)

Alternatively, run the automated install script (see Step 3b below).

Step 3b: Automated Library Install (PowerShell)

Copy and paste this into Windows PowerShell to check for and install all required libraries automatically. This uses the Arduino CLI bundled with Arduino IDE.

# TC_Charger -- Automated Library Installer
# Run in Windows PowerShell (not Command Prompt)

$cli = "C:\Program Files\Arduino IDE\resources\app\lib\backend\resources\arduino-cli.exe"

if (-not (Test-Path $cli)) {
    # Try alternate install locations
    $cli = "$env:LOCALAPPDATA\Programs\Arduino IDE\resources\app\lib\backend\resources\arduino-cli.exe"
}

if (-not (Test-Path $cli)) {
    Write-Host "ERROR: Arduino CLI not found. Install Arduino IDE first." -ForegroundColor Red
    Write-Host "Download: https://www.arduino.cc/en/software"
    exit 1
}

Write-Host "Using Arduino CLI: $cli" -ForegroundColor Cyan
Write-Host ""

# Required libraries (exact names for arduino-cli)
$libraries = @(
    "FastLED",
    "U8g2",
    "Adafruit AHTX0",
    "Adafruit BMP280 Library",
    "TinyGPSPlus",
    "PubSubClient"
)

# Get currently installed libraries
$installed = & $cli lib list 2>$null

foreach ($lib in $libraries) {
    if ($installed -match [regex]::Escape($lib)) {
        Write-Host "[OK]      $lib (already installed)" -ForegroundColor Green
    } else {
        Write-Host "[INSTALL] $lib ..." -ForegroundColor Yellow
        & $cli lib install $lib
        if ($LASTEXITCODE -eq 0) {
            Write-Host "          $lib installed successfully" -ForegroundColor Green
        } else {
            Write-Host "          FAILED to install $lib" -ForegroundColor Red
        }
    }
}

Write-Host ""
Write-Host "All libraries checked. You can now compile the firmware." -ForegroundColor Cyan
Write-Host ""

# Also check for ESP32 board package
$boards = & $cli board listall 2>$null
if ($boards -match "ESP32S3") {
    Write-Host "[OK]      ESP32 board package installed" -ForegroundColor Green
} else {
    Write-Host "[INSTALL] ESP32 board package ..." -ForegroundColor Yellow
    & $cli core install esp32:esp32
}

Step 4: Upload

  1. Open TC_Charger_MainBrain/TC_Charger_MainBrain.ino
  2. Select your port under Tools > Port
  3. Click Upload (arrow button)
  4. Open Serial Monitor or Putty at 115200 baud
  5. Press the RST button on the board
  6. You should see the boot banner and status messages

Troubleshooting

Boot loop with "partition table error":

E (29) flash_parts: partition 3 invalid - offset 0x310000 size 0x300000 exceeds flash chip size 0x400000

This means Flash Size is wrong (set to 4MB instead of 16MB) or a previous upload left a bad partition table. Fix:

  1. Tools > Flash Size > 16MB (128Mb)
  2. Tools > Erase All Flash Before Sketch Upload > Enabled
  3. Upload the sketch
  4. After successful boot, set Erase All Flash back to Disabled (so NVS settings are preserved on future uploads)

Blank serial output (nothing in Putty):

  • Check Tools > USB CDC On Boot is set to Disabled
  • Make sure Putty is on the correct COM port at 115200 baud
  • Press RST on the board after opening Putty
  • In Putty settings: Terminal > check "Implicit CR in every LF" (fixes staircase text)

Sketch too big / exceeds available space:

  • Check Tools > Partition Scheme is set to "16M Flash (3MB APP/9.9MB FATFS)"
  • The default 1.2MB APP partition is too small for this firmware

Upload fails / can't connect:

  • Try holding the BOOT button while clicking Upload, release after "Connecting..." appears
  • Check that no other program (Putty, Serial Monitor) has the COM port open during upload
  • Try a different USB cable (some are charge-only, no data)

Wiring Summary

ESP32-S3 Main Brain Pin Map

GPIO Function
4 CAN TX (to SN65HVD230 TXD)
5 CAN RX (from SN65HVD230 RXD)
6 NEXT button (active LOW, pullup)
7 HOLD button (active LOW, pullup)
8 I2C SDA (OLED, AHT20, BMP280, QMC5883L)
9 I2C SCL (shared bus)
15 GPS RX (from GPS module TX)
16 GPS TX (to GPS module RX)
17 RS485 TX (to RS485 DI)
18 RS485 RX (from RS485 RO)
48 WS2812B RGB LED (onboard)

CAN Bus Wiring

ESP32-S3 GPIO4 ---> SN65HVD230 TXD
ESP32-S3 GPIO5 <--- SN65HVD230 RXD
SN65HVD230 VCC ---> 3.3V
SN65HVD230 GND ---> GND
SN65HVD230 S   ---> GND (normal mode)
SN65HVD230 CANH --> Charger CANH --[120R]--> CANL
SN65HVD230 CANL --> Charger CANL

Healthy idle bus: CANH-CANL differential near 0V.

Contributing

Contributions are welcome under the CC BY-NC-SA 4.0 license:

  1. Fork the repository
  2. Create a feature branch
  3. Submit a pull request with clear description
  4. All contributions become open source under the same license

For commercial licensing inquiries, open an issue or contact the project owner.

Disclaimer

This project involves high-voltage battery charging. Incorrect wiring, configuration, or use can cause fire, explosion, property damage, or injury. Use at your own risk. The authors assume no liability for any damages resulting from the use of this project.

Always verify your pack voltage, current limits, and wiring before enabling charging. Never leave a charging battery unattended.

About

Open source ESP32-S3 controller for HK-LF-115-58 6.6kW EV on-board charger. CAN bus control, BLE/WiFi telemetry, energy tracking, buddy charge mode. CC BY-NC-SA 4.0.

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