Design of a simplified Charging Equalizer for Safety Enhancement of Electric Vehicle

Lithium-ion (Li-ion) batteries are commonly used in electric vehicle (EV) applications due to their higher energy density, longer lifespan, and better performance. However, there are few limitations of Li- ion setup including overcharging, undercharging, risk of explosion and nonlinear life cycle. These issues when sustained over a period, significantly reduces the effective charging capacity and the efficiency of the battery pack. It is estimated that the conventional charging cycles deviate above the permissible variation up to $7 \%$ of the long time average of the installed pack. For the dynamically varying loads, this deviation increased up to even $15 \%$. Keeping an objective of maintaining the duty cycle deviation within $10 \%$, this paper proposes a simple Charge equalizer that uses Arduino based controller to handle the relays for changing the charging process from one cell to another. Different combinations of relay activations tried for extended charging cycle. The dynamic variation of cell voltages, calculating maximum and minimum transient voltages, controlling charge/discharge cycles are the few topics discussed in this paper. It is found from the experiment that up to 7 charge cycles the deviation was about $10 \%$ and beyond which it remains constant. Final conclusion and future scope have discussed in brief.