18650 LiPo Battery Manager Acts as a Power Bank for Projects

Manuel Alfonso designed an all-in-one LiPo battery manager that can work as a battery charger, fuel gauge, and dual-rail power supply.

Abhishek Jadhav
3 years agoInternet of Things

Last year, Manuel Alfonso published a project on a 12-bit programmable sound-reactive NeoPixel ring. Now, the developer has come up with a 18650 LiPo battery manager that can work as a battery charger, battery monitor, and dual-rail power supply.

The hardware is based on a single-cell LiPo designed in such a way that it can be connected to a 18650 battery case acting as a power bank for the project. The battery charging is managed by Texas Instruments' BQ24075 IC, which is a standalone linear battery charger with Dynamic PowerPath Management. With the DPPM feature, it gives output whenever a source is connected to the USB port.

To understand the charging process, let us look at the three phases. In the conditioning pre-charge phase, it charges at 100mA until the battery rises to 3V. The constant current fast charge will charge through the configured DIP switch until the battery reaches 4.2V. The last phase of charging involves 'constant voltage tapering' as it holds to a constant voltage while the current changes as the battery approaches full charging.

The board also features a TI BQ27441-G1A fuel gauge that enables it to predict battery capacity alongside other operational characteristics. "The fuel gauge measures the charging and discharging of the battery by monitoring the voltage across a small-value sense resistor (10mΩ)," Alfonso notes.

This fuel gauge IC works with the STMicroelectronics' 32-bit microcontroller that's connected to a 0.91" OLED display. The display is used to show operational characteristics like the state of charge, battery voltage, full-charge capacity, temperature, and many more. "Once the battery is inserted, the information displayed is based on the IC algorithm with the default register data," Alfonso explains. "As we take charge and discharge iterations, these registers will be adjusted to show more accurate values."

Dual rail power supply feature of the board allows it to provide 3.3V and 5V power rail. The 5V power rail gives 2A output current with a high-efficiency step-up converter, while the 3.3V has a synchronous step-down converter. To power the MCU and the display port, 3.3V power rail is used.

Alfonso has worked on STM32CubeID for the source code, which is available on the GitHub repository. The board is for sale now via Tindie, priced at $20.

Abhishek Jadhav
Abhishek Jadhav is an engineering student, freelance tech writer, RISC-V Ambassador, and leader of the Open Hardware Developer Community.
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