# Multi-Mode Lithium-Ion Battery Balancing Circuit Based on Forward Converter with Resonant Reset
###### Abstract
When there are few cells with high power, the C2P balancing method can improve balancing. However, the balancing speed of this method is very slow when there is only one cell with low power in the pack. In contrast to C2P, Pack-to-Cell (P2C), as shown in [31; 32], refers to the transfer of energy from the whole battery pack to a cell. This approach enhances balancing speed when there are fewer cells with low power. Like C2P, the balancing speed of P2C is also very slow when there is only one cell with high power in the battery pack. Furthermore, C2P and P2C will suffer from external energy loss due to the unrelated cells in the battery pack being charged or discharged. Any Cell-to-Any Cell (AC2 AC), as shown in [33; 34; 35], can realize transmission of energy between any cells. The advantage of this approach is that any cell within the battery pack can participate in the balancing process and transfer energy to the target cell, thereby improving balancing efficiency and reducing unnecessary energy loss. However, each cell needs to be equipped with a balancing main circuit to implement this method. Although the circuit is scalable, it can easily lead to complexities and high cost. Furthermore, modular design can also result in inevitable parameter variations among the balancing main circuits. For example, [PERSON] et al. [33] used a multi-winding transformer as the balancing main circuit, which offers the advantages of small size and low cost. However, ensuring the consistency of each winding's parameter is challenging. [PERSON] et al. [34] used switched capacitors to implement AC2 AC, leading to lower complexity and ease of scalability. However, the massive use of capacitors and MOSFETs in the circuit leads to parameter variations among the components and increased cost. In [35], [PERSON] et al. used a resonant reset forward converter to achieve balancing. This type of forward converter has a simple structure and achieves demagnetization through LC resonance between the excitation inductance on the primary side of the converter and the capacitors connected in parallel to the MOSFETs. Additionally, this circuit features low design complexity and ease of scalability. However, the widespread use of forward converters increases circuit cost and mismatch issues can arise due to variations in the inductance values of the converter and resonant capacitance of the resonant capacitor in practice. In addition, AC2 AC balancing is typically performed automatically based on the voltage (or SOC) of each cell within the battery pack. This results in a dispersed energy transfer during the balancing process, leading to longer balancing times. Compared with the aforementioned balancing methods, Multi-Cell-to-Multi-Cell (MC2 MC) [36; 37; 38] not only allows multiple cells to participate in a single balancing process for energy transfer, but also enables energy transfer between battery clusters. The concentration of energy transfer during the balancing process enhances balancing speed and reduces energy losses during the transfer. The circuit structure of MC2 MC is typically composed of a common balancing main circuit and a switch matrix. [PERSON] et al. [36] proposed a balancing circuit based on a matrix LC resonant converter (MLCC) balancing circuit, which consists of an LC resonant converter and a relay matrix. This balancing circuit features a simple circuit structure and low cost. [PERSON] et al. [37] proposed a balancing circuit based on a bipolar-resonant LC converter (BRLCC), which utilizes an LC resonant converter as the balancing main circuit and introduces a symmetrical switch matrix composed of bidirectional MOSFETs, further simplifying the structure of the switch matrix. [PERSON] et al. [38] proposed a balancing circuit based on a Buck-Boost converter, which simplifies the structure of the switch matrix through cell grouping. However, the LC resonant converters used in [36; 37; 38] often require bulky magnetic components and high-voltage switches when applied to balance high-voltage and large-capacity battery packs [39].