Battery Management System (BMS) with Buck-Boost Converter

Brief

Many low-power digital devices rely on lithium batteries, which are prevalent today. As these batteries discharge, voltage drops, leading to operational issues for devices with specific voltage requirements. For instance, if a device needs a constant voltage of 3.4V, it ceases to function once the battery drops below this level. Additionally, powering devices at 3.3V or 5V is common. This module addresses these challenges.

Features

The key components of the module include:

• Charging Circuit: Utilizing the MCP73831, this circuit facilitates the selection of charge current via a resistor and incorporates an indicator diode.

• Protection Circuit: Protection is ensured by DW01A and FS8205A. The FS8205A connects the battery's negative to the common ground, with DW01A controlling battery operation. The transistor disconnects the battery in cases of discharge, overcharge, short circuit, etc.

• DC-DC Buck-Boost Converter: Employing TPS63020DSJR, this component enables voltage conversion. The goal is to maintain a constant voltage level regardless of the battery charge, acting as a step-up converter when voltage is low and a step-down converter when it's high.

In summary, this module facilitates battery charging, provides protection, and allows for adjustable output voltage.

Refer to the complete schematic in BMS_Buck-Boost.pdf.

Module Appearance

Pinouts

• -B and +B are used to connect the battery.
• +B, +V, and GND are for connecting to the load, with +B used for measuring battery voltage.

Notes

• While using the module during charging and securing the load, certain limitations exist when the level on the VBUS line is high. At this point, transistor Q2 (refer to the schematic here) doesn't pass the voltage. This is done to optimize battery charge. If you want to use VBUS for the DC-DC converter during charging, employ diode D4 and an additional diode to prevent current from +VCC_IN to +BATT.