Low Voltage Battery Capacity Optimization Method for Vehicles by Connecting Supercapacitor in Series

Most electrical vehicles and internal combustion engine vehicles are implementing lithium-ion batteries as one of low voltage power source for 12V/48V loads, cooperating with vehicle HV/LV DCDC. Energy demands are not the dominant factor for determining battery capacity thanks to high energy density of lithium-ion battery. However, power demands with specified voltage limit will lead to a large battery capacity, especially when battery requires to run under cold environments. Implementing large battery capacity means bigger battery pack dimensions, heavier weight, and higher cost which will have an influence on vehicle’s overall performance and sales. Thus, OEMs consider battery capacity as a key factor for selecting low voltage batter supplier during sourcing. This paper introduces a method where supercapacitor could be integrated into the battery pack and could be controlled to be connected with lithium-ion battery module in series according to detected profile by BMS or control signals from vehicle, which could solve limited power problems of lithium-ion battery and will drive a small battery size with lower overall cost of battery pack. Related simulations result will also be covered in this paper to prove the feasibility of above concept. Furthermore, this technology could also be applied on similar energy storage situation, including energy storage station and so forth.