Battery Management Unit

Introduction

The Battery Management Unit serves several critical functions:

• Communicates with slave cell monitoring units (CMUs) over IsoSPI
• Filters and monitors reported cell voltages and temperatures
• Runs cell balancing algorithm
• Interfaces to charger for charge state management and pre-charge commands
• Includes shutdown interface for Insulation Monitoring Device (IMD), precharge resistor thermal sensor (PDOC), connector interlocks, and BMU battery state detection

Design Requirements

FSAE Rules 2023

The core BMU (AMS - Accumulator Management System) requirements include:

• Communication capability with cell monitoring units
• Ability to trip shutdown circuit via relay during fault conditions
• Fault indicator light implementation (hardware-based for Rev B)

IMD Requirements

• Relay present to trip shutdown circuit if 12V status signal is not high
• No programmable logic permitted
• Fault indicator light required

Additional Design Constraints

• Galvanic isolation between GLV and Tractive circuits
• 12.7mm clearance for uncoated surfaces or 4mm under conformal coating
• 3mm clearance for non-coated 600V nets; 1.105mm for conformal coated

Team-Specific Requirements

Including SD card logging, dual IsoSPI interfaces, USB-C debugging, dual CAN bus connections, and indicator LEDs.

Rev B Additional Requirements

Including latching of shutdown segments, non-programmable LED drivers, and auxiliary coil detection.

Design Solution & Assembly

The PCB was hand-placed and vapor phase oven soldered, with rails positioned for potential pick-and-place automation.