battery battery-management-system charger i2c li-ion-battery mlab mlab-module kicad kicad-project mlab-kicad bms power-supply


Dual-cell Li-Ion Battery management system.


This is an open-source hardware design, one of the modules from the MLAB labolatory system.

LION2CELL01D - Li-ion dual-cell Battery Management Module



The LION2CELL01D is an integrated battery management solution for 18650 Li-ion batteries. It is designed to manage the charging, balancing, and monitoring of two series-connected Li-ion cells. This module measures the remaining energy, voltage, and temperature of the batteries, and protects against over-voltage and over-draining conditions.


  • Charging and Balancing: Supports charging, balancing, and termination with temperature protection.
  • Gas-gauging: Temperature-compensated gas-gauging for accurate remaining energy estimation.
  • Protection: Over-voltage, over-current protection, but no under-voltage protection (the module operates until battery depletion).
  • Communication: Supports I2C and HDQ communication interfaces.

Technical Specifications

  • Power Supply: 12 V @ 2 A
  • Charging Current: Factory set to approximately 1.3 A
  • Battery Holder: 2x 18650
  • Interfaces: I2C, HDQ
  • Integrated Circuits:
  • BQ24103 for charging
  • BQ34Z100 for fuel gauging
  • Dimensions: 80.77 x 60.45 x 16 mm


Pin Signal Description
1 PG Power Good
2 STAT2 Status Indicator
3 GND Ground
4 CE Chip Enable
5 STAT1 Status Indicator
6 CMODE Configuration Mode


The module is constructed with three main functional blocks: 1. Charging Circuitry: Manages the charging process of the two series-connected Li-ion cells. 2. Measurement Circuitry: Measures the voltage, current, and temperature of the cells. 3. Balancing and Protection Circuitry: Ensures cell voltage balancing and provides protection against over-voltage.

Important Considerations

  • Regular charging is required (at least once every six months) to maintain the batteries within operational voltage ranges.
  • Specific resistor values and settings are used for the voltage measurement, ensuring accurate readings without exceeding voltage limits.
  • The module is equipped with a balancing circuit that discharges one of the cells to match the voltage of the other, with a discharge current around 10 mA.

Setup and Configuration

  1. Installation:
  2. Check the PCB for proper soldering.
  3. Insert the batteries in the designated order: position 1 first, followed by position 2.
  4. Verify the operation of the charging function by connecting a 12V adapter.

  5. Software:

  6. Use to upload parameters to the energy measurement circuit.
  7. Parameters are tailored for Panasonic NCR18650B or INR18650MJ1 cells; adjustments are needed for other types.
  8. Conduct at least one charge/discharge cycle for accurate energy measurements.