"Integration of Solar-Wind Energy for EV Battery Charging with Active Battery Equalization"

Abstract

Electric vehicles (EVs) are a cornerstone of sustainable transportation, but their real‑world performance suffers from two major issues: (i) voltage and state‑of‑charge (SOC) imbalances among series‑connected battery cells, which reduce usable capacity, and (ii) dependence on grid electricity that may come from fossil fuels. On‑board renewable energy (solar and wind) offers a solution for the second issue, but its benefits are only fully realized if the battery pack is balanced. This paper presents a detailed MATLAB/Simulink simulation study of a solar‑wind hybrid EV that incorporates a sequential active battery equalization system designed for parked charging (e.g., during daytime parking at work or home). The system consists of constant DC sources representing 535 W photovoltaic (PV) and 135 W wind turbine output, a five‑cell series battery pack initially mismatched from 10.5 V to 13.0 V, and a simple but effective minimum‑voltage selection algorithm. During equalization, the vehicle load is disconnected (parked condition), so the entire renewable power (670 W) can be routed to the weakest battery using relay‑based switching logic. Simulation over 10,000 seconds shows that all five voltages converge to 13.0 V (final spread <0.1 V), and SOC equalizes from 70–86.7% to ≈87%. Consequently, the usable pack energy increases by 10.2%, which translates into a theoretical driving range extension of 10–15%. A comparison with a case where equalization is disabled confirms that without active balancing the imbalance persists, wasting renewable energy. The model is a proof‑of‑concept with explicitly stated simplifications (constant renewables, linear battery model), yet it clearly demonstrates the feasibility and benefit of combining hybrid renewable charging with low‑cost sequential equalization. The work is particularly relevant for sunny and windy regions like India, where EVs can harvest significant energy while parked.