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Seplos BMS 10E Bluetooth Reader for Raspberry Pi

Python script to read Seplos 10E BMS data via Bluetooth Low Energy (BLE) on Raspberry Pi.

Credits

This project is based on the excellent reverse engineering work by syssi and the esphome-seplos-bms project. They did the heavy lifting of decoding the Seplos BMS protocol, which this script ports to Python for Raspberry Pi use.

Features

  • Read cell voltages, temperatures, current, SOC, SOH and more
  • Decode switch states (charge/discharge/current limit/heating)
  • Decode system status (charging/discharging/float/standby/shutdown)
  • Decode alarm events with human-readable messages
  • Support for continuous monitoring mode
  • MQTT publishing with configurable topic prefix
  • JSON output for integration with other systems
  • Auto-reconnect on connection loss

Requirements

  • Raspberry Pi with Bluetooth (3B+, 4, 5, Zero 2 W, etc.)
  • Seplos 10E BMS with Bluetooth module
  • Python 3.8+

Installation

1. Install Dependencies

sudo apt-get update
sudo apt-get install python3-pip
pip3 install bleak paho-mqtt

2. Download Script

wget https://raw.githubusercontent.com/YOUR_USERNAME/YOUR_REPO/main/seplos_bms_ble.py
chmod +x seplos_bms_ble.py

3. Configure MAC Address

Find your BMS MAC address:

sudo bluetoothctl
[bluetooth]# scan on
# Look for device starting with 60:6E:41 (Seplos OUI)
[bluetooth]# quit

Edit the MAC address in the script:

MAC_ADDRESS = "60:6E:41:16:73:DC"  # Your BMS MAC address

4. Fix Bluetooth Permissions

sudo usermod -a -G bluetooth $USER
# Logout and login again for group changes to take effect

Usage

One-shot reading (default)

sudo python3 seplos_bms_ble.py

Outputs full formatted data to console.

Monitor mode (continuous)

# Every 20 seconds (default)
sudo python3 seplos_bms_ble.py monitor

# Every 5 seconds
sudo python3 seplos_bms_ble.py monitor 5

# Every minute
sudo python3 seplos_bms_ble.py monitor 1m

JSON output

# One-shot
sudo python3 seplos_bms_ble.py json

# Continuous every 10 seconds
sudo python3 seplos_bms_ble.py json 10

MQTT mode

# Default: localhost:1883, topic: seplosbms, interval: 20s
sudo python3 seplos_bms_ble.py mqtt

# Custom interval
sudo python3 seplos_bms_ble.py mqtt 10

# Custom MQTT broker
sudo python3 seplos_bms_ble.py mqtt --host 192.168.1.50 --port 1883

# Custom topic prefix
sudo python3 seplos_bms_ble.py mqtt --topic mybms

# Combined
sudo python3 seplos_bms_ble.py mqtt 30 --host 192.168.1.50 --port 1883 --topic seplosbms

Help

sudo python3 seplos_bms_ble.py --help

Systemd Service (Auto-Start)

To run the script automatically on boot as a systemd service:

1. Install Service File

# Copy service file to systemd
sudo cp seplos-bms-ble.service /etc/systemd/system/

# Reload systemd
sudo systemctl daemon-reload

2. Configure Service (Optional)

Edit the service file to match your setup:

sudo nano /etc/systemd/system/seplos-bms-ble.service

Key settings to adjust:

Setting Default Description
ExecStart ... mqtt Command to run. Change mode/interval/topic here
User pi User to run as
WorkingDirectory /home/pi Where the script is located

Example with custom MQTT broker:

ExecStart=/usr/bin/python3 /home/pi/seplos_bms_ble.py mqtt 30 --host 192.168.1.50 --topic seplosbms

3. Enable and Start Service

# Enable auto-start on boot
sudo systemctl enable seplos-bms-ble.service

# Start service now
sudo systemctl start seplos-bms-ble.service

# Check status
sudo systemctl status seplos-bms-ble.service

4. View Logs

# Follow logs in real-time
sudo journalctl -u seplos-bms-ble.service -f

# View last 50 lines
sudo journalctl -u seplos-bms-ble.service -n 50

# View logs since last boot
sudo journalctl -u seplos-bms-ble.service --since today

5. Manage Service

# Stop service
sudo systemctl stop seplos-bms-ble.service

# Restart service
sudo systemctl restart seplos-bms-ble.service

# Disable auto-start
sudo systemctl disable seplos-bms-ble.service

MQTT Topics

With default topic prefix seplosbms:

Topic Description Unit
seplosbms/voltage Total battery voltage V
seplosbms/current Battery current A
seplosbms/power Calculated power W
seplosbms/soc State of charge %
seplosbms/soh State of health %
seplosbms/capacity_remaining Remaining capacity Ah
seplosbms/capacity_total Total capacity Ah
seplosbms/cycles Charge cycles count
seplosbms/port_voltage Port voltage V
seplosbms/temp/ambient Ambient temperature C
seplosbms/temp/mosfet MOSFET temperature C
seplosbms/temp/average_cell Average cell temperature C
seplosbms/temp/cell_1 ... cell_8 Individual cell temperatures C
seplosbms/cell/1/voltage ... cell_24/voltage Individual cell voltages V
seplosbms/cell/1/balancing ... Balancing state ON/OFF
seplosbms/cell/1/disconnected ... Disconnected state ON/OFF
seplosbms/cell/min_voltage Minimum cell voltage V
seplosbms/cell/max_voltage Maximum cell voltage V
seplosbms/cell/delta Cell voltage delta V
seplosbms/cell/average Average cell voltage V
seplosbms/switch/discharge Discharge switch ON/OFF
seplosbms/switch/charge Charge switch ON/OFF
seplosbms/switch/current_limit Current limit switch ON/OFF
seplosbms/switch/heating Heating switch ON/OFF
seplosbms/system/discharging System discharging ON/OFF
seplosbms/system/charging System charging ON/OFF
seplosbms/system/float_charge Float charging ON/OFF
seplosbms/system/standby Standby mode ON/OFF
seplosbms/system/shutdown Shutdown mode ON/OFF
seplosbms/alarms/count Number of active alarms count
seplosbms/alarms/list Semicolon-separated alarm list text
seplosbms/alarms/event_1 ... event_8 Alarm bitmask hex hex
seplosbms/info/model Device model text
seplosbms/info/hardware Hardware version text
seplosbms/info/software Software version text
seplosbms/info/battery_type Battery chemistry text
seplosbms/info/can_protocol CAN protocol text
seplosbms/info/rs485_protocol RS485 protocol text
seplosbms/info/timestamp Reading timestamp ISO8601
seplosbms/json Complete data as JSON JSON
seplosbms/status Online status (retained) online

Example Output

============================================================
SEPLOS BMS 10E
============================================================

Model: CAN:Victron | HW: 1101-SP76 | SW: 16.6
Type: LFP | CAN: Victron | RS485: Pylontech

--- Cells (16) ---
   1: 3.446V
   2: 3.449V
   3: 3.444V
   4: 3.445V
  ...
  Min: 3.444V (Cell 3)
  Max: 3.449V (Cell 2)
  Delta: 0.005V | Avg: 3.447V

--- Temps ---
  T1: 17.4C
  T2: 17.1C
  T3: 16.9C
  T4: 17.6C
  Ambient: 22.5C | MOSFET: 18.1C
  Avg Cell: 17.2C

--- Main ---
  Voltage: 55.15V | Current: -0.90A | Power: -49.6W
  SOC: 98.2% | Remaining: 275.0Ah / 280.0Ah
  Cycles: 550 | SOH: 100.0% | Port: 55.17V

--- Switches ---
  Discharge: ON | Charge: ON
  CurrentLimit: OFF | Heat: OFF

--- System ---
  Discharging: False | Charging: False | Float: False
  Standby: True | Shutdown: False

--- Alarms ---
  ! Total high voltage alarm

============================================================

Protocol Details

The Seplos BMS uses a proprietary protocol over BLE with the following characteristics:

  • Service UUID: 0000ff00-0000-1000-8000-00805f9b34fb
  • Notify Characteristic: 0000ff01-0000-1000-8000-00805f9b34fb (handle 0x12)
  • Control Characteristic: 0000ff02-0000-1000-8000-00805f9b34fb (handle 0x14)
  • Frame format: 0x7E [VER ADDR CID1 CID2 LEN payload CRC] 0x0D
  • CRC: XMODEM (same as ESPHome implementation)

Resolution of BMS values:

Value Resolution Format
Cell voltage 1 mV uint16 * 0.001
Temperature 0.1 C (uint16 * 0.1) - 273.15 K
Current 10 mA int16 * 0.01
Total voltage 10 mV uint16 * 0.01
SOC/SOH 0.1 % uint16 * 0.1
Capacity 10 mAh uint16 * 0.01

Troubleshooting

Permission denied

sudo usermod -a -G bluetooth $USER
# Logout and login again for group changes to take effect

Connection timeout

  • Move Raspberry Pi closer to BMS
  • Check if BMS Bluetooth LED is blinking (pairing mode)
  • Verify MAC address with bluetoothctl scan on

MQTT connection refused

  • Check if MQTT broker is running: systemctl status mosquitto
  • Verify firewall rules for port 1883
  • Test with mosquitto_pub -t test -m "hello"

Service fails to start

# Check for errors
sudo journalctl -u seplos-bms-ble.service -n 50

# Test script manually first
sudo python3 /home/pi/seplos_bms_ble.py

# Check if script path is correct in service file
sudo systemctl cat seplos-bms-ble.service

Wrong switch/alarm states

Make sure you are using the latest version of this script. Earlier versions had incorrect offset calculations for switch and alarm data.

License

MIT License - See LICENSE file

Acknowledgments

About

Monitor Seplos BMS (V2) over BLE on Raspberry PI

Topics

bluetooth-low-energyraspberry-piseplos-bms

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