Battery Pack Cell Balancing and Diagnosis Device for Electric Bikes

Abstract

Electric bikes commonly utilize Lithium Iron Phosphate (LiFePO4) battery packs composed of multiple cells connected in series to achieve high voltage requirements, where the overall performance, safety, and lifespan depend heavily on the equilibrium of individual cells. A single weak or degraded cell can significantly reduce the overall capacity and reliability of the entire pack, yet professional cell-level diagnostic equipment remains expensive and inaccessible to local workshops and general EV users in Pakistan. This project presents a low-cost, discrete component-based Passive Battery Cell Balancing and Diagnostic Device designed specifically for a battery configuration. Unlike active balancing systems that require complex energy transfer components, this system utilizes a switched shunt resistor technique to dissipate excess energy from higher-voltage cells through power resistors, ensuring all cells reach a uniform state of charge. The device performs comprehensive diagnostics by monitoring real-time voltage and status through an analog control logic powered by NE555 timers and Darlington pair drivers. By enabling precise detection and balancing of cells through manual threshold tuning, the proposed solution prevents unnecessary full-pack replacements, making EV maintenance more economical and sustainable. Portable, user-friendly, and locally manufacturable using readily available electronic components, this device offers an affordable alternative to industrial-grade analyzers and directly supports the growing electric vehicle ecosystem.