Voltage equalization of lithium iron phosphate batteries cooperating with supercapacitors

Abstract

This paper is aimed to develop a voltage equalization circuit for lithium iron phosphate batteries cooperating with supercapacitors. In this proposed equalizer, a bi-directional dcdc converter circuit is utilized to deliver the redundant energy to supercapacitors such that the unequal battery voltage problem can be solved, while the energy loss can be minimized simultaneously. The study begins with the charging and discharging of batteries of interest. Then, the cell balancing circuit is constructed with the designated control procedure. This prototype has been extensively validated in the laboratory. Experimental results confirm the feasibility of the proposed approach for battery voltage balancing applications.

A Battery Cell Equalisation System Based on a Supercapacitors Tank and DC–DC Converters for Automotive Applications

“…The system is based on bi-directional buck-boost converters, using the fast charge ability of the SCs, also depicted in [17] and relatively high efficiency proven in [18,19]. Eventually, these SCs applications show that they could be used as energy storage for battery cell equalisation, as suggested in [20]. In addition to this, considering the SCs' mature integration [10,11] and control in the EVs Battery-SCs energy storage [12][13][14], overall financial benefits [15,16], and fast charging abilities and energy fluctuation mitigation [17][18][19], it could be suggested that the SCs energy tank could be used as a part of the battery cell equalisation system [20] further developed to utilise the regenerative brake energy from the electric drivetrain.…”

“…Despite the selected topology, one of the most critical sub-systems determining the overall system's efficiency and flexibility is the electronic converter, transferring the energy for the equalisation process. Therefore, the studied research results show that the power electronic unit topology selection and consecutively design and integration are of essential importance [13,16,20,[29][30][31][36][37][38][39][40].…”

“…The required capacitors' energy W C is given with the integral of the power P C over the time t [3,4,6,7,12,19,20,29,30]:…”

“…The SCES charge and discharge basic equations [3,4,6,7,12,19,20,29,30] necessary for the simulation models are given in Table 2. The results of the simulations present the comparison between constant voltage (CV) and constant current (CC) illustrated, respectively, with block diagrams in Figures 3 and 4 Figure 5 shows the results for CV charging as follows: (A) the transi cess continues for 17.5 s, e.g., five times the time constant 𝑇 = 3.5 s wi voltage 𝑉 = 10 V ; (B) the peak current at the beginning of the tra 499.86 A, and the average current is 100.72 A, which are considered una selected battery cells; (C) the peak capacitor loss is 44.64 W, and the a loss is 17.61 W; (D) the peak power delivered to the energy storage is 12 average power is 493.13 W; (E) the peak energy is 8629.12 J, and the lated energy is 6124 J.…”