Design of a Microcontroller-Based Battery Management System for Solar Home Systems in Off-Grid Communities in Sokoto State

Many rural communities in Sokoto State, North West Nigeria, rely on small solar home systems for basic lighting and phone charging needs, but battery degradation due to overcharging, deep discharge, and thermal stress significantly shortens battery service life and increases household energy costs. This project presents the design of a microcontroller-based battery management system for lead-acid batteries used in solar home installations in off-grid communities. The system employs voltage and current sensors to monitor charge and discharge rates, an NTC thermistor for temperature compensation, and an ATmega328P microcontroller running a state-of-charge estimation algorithm based on Coulomb counting with voltage correction. Overcharge protection is achieved through a MOSFET-based charge disconnect relay, while a low-voltage disconnect circuit prevents deep discharge beyond 20 percent state of charge. An LCD display presents battery status to household users. The system was tested under simulated solar charging profiles and varied household load patterns over 30 consecutive charge-discharge cycles. Results showed that batteries managed by the system retained 91 percent of initial capacity after 30 cycles, compared to 74 percent for batteries under a standard solar charge controller. Installation and component cost for the BMS was approximately 7,200 Naira per unit. The study recommends subsidized distribution of the BMS through rural electrification programme channels to extend battery life and reduce replacement costs for low-income households. Keywords: battery management system, solar home system, off-grid electrification, lead-acid battery, Sokoto State