Double-Tiered Switched-Capacitor Battery Charge Equalization Technique

TLDR

The automotive industry is moving toward hybrid, plug‑in hybrid, and fully electric vehicles, making reliable energy storage units—batteries or ultracapacitors—critical, and requiring charge equalization of series‑connected cells to mitigate capacity imbalances from manufacturing, driving conditions, and use. This work introduces a double‑tiered capacitive charge shuttling technique to balance battery‑cell voltages in a battery system. The authors vary system parameters, evaluate their impact, and compare the resulting performance to a single‑tiered approach. MATLAB simulations demonstrate a substantial improvement in charge transport with the new topology, and experimental data confirm the simulation results.

Abstract

The automobile industry is progressing toward hybrid, plug-in hybrid, and fully electric vehicles in their future car models. The energy storage unit is one of the most important blocks in the power train of future electric-drive vehicles. Batteries and/or ultracapacitors are the most prominent storage systems utilized so far. Hence, their reliability during the lifetime of the vehicle is of great importance. Charge equalization of series-connected batteries or ultracapacitors is essential due to the capacity imbalances stemming from manufacturing, ensuing driving environment, and operational usage. Double-tiered capacitive charge shuttling technique is introduced and applied to a battery system in order to balance the battery-cell voltages. Parameters in the system are varied, and their effects on the performance of the system are determined. Results are compared to a single-tiered approach. MATLAB simulation shows a substantial improvement in charge transport using the new topology. Experimental results verifying simulation are presented.