Capacitor Network Cell Balancing for Battery Packs
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Solution Overview
Problem
Existing battery packs connected in series or parallel face challenges in achieving balanced charging and discharging due to capacity differences, leading to reduced available capacity and unbalanced aging, particularly exacerbated by frequent and deep charge/discharge cycles in electric vehicles, where traditional balancing circuits suffer from inefficiencies, high heat generation, and limited balancing ability.
Innovation Solution
A cell balancing device based on a capacitor network with a cascadable balanced battery pack structure, utilizing a chain-type energy storage capacitor network and simplified switch control, enabling high-frequency and efficient balancing with low power consumption, suitable for both lead-acid and lithium battery packs, and applicable to high-voltage battery packs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If passive component (power resistor) is used for charge balancing, then charging voltage can be regulated, but heat generation increases and energy consumption increases
Solution Approach 1:
The patent introduces an energy storage capacitor as an intermediary component between battery cells with different voltages. The capacitor temporarily stores energy from higher-voltage cells and transfers it to lower-voltage cells, enabling direct energy transfer without resistive dissipation. This mediator approach eliminates the need for power resistors and significantly reduces energy loss during the balancing process.
Solution Approach 2:
The patent replaces the traditional passive resistor-based mechanical/thermal balancing system with an active electronic switching system using MOSFETs and capacitors. This substitution transforms the balancing mechanism from a thermal/dissipative process to an electrical energy transfer process, eliminating heat generation and improving energy efficiency.
2Power
If passive component (power resistor) is used for charge balancing, then charging voltage can be regulated, but balancing ability is limited and balancing time is long
Solution Approach 1:
The patent implements a dynamic switching system using MOSFETs that can rapidly connect and disconnect battery cells from the balancing circuit based on real-time voltage differences. This dynamic control enables the system to respond quickly to imbalance conditions and adjust the balancing current accordingly, significantly improving balancing speed compared to static resistor-based systems.
Solution Approach 2:
The patent employs periodic switching of MOSFETs to create pulsed current flow between battery cells through the energy storage capacitor. This periodic action allows for controlled, high-current charge transfer that can rapidly equalize voltage differences between cells, enhancing balancing ability while maintaining precise voltage regulation.
3Weight of stationary object
If switch capacitor balancing circuit is used, then size is small and weight is light, but switch control complexity increases and direct-current level inconsistency occurs
Solution Approach 1:
The patent merges multiple functions into the energy storage capacitor, which simultaneously serves as a voltage reference, an energy transfer medium, and a DC level equalizer for the switching circuit. By combining these functions into a single component, the system reduces control complexity while maintaining the benefits of a compact, lightweight design.
Solution Approach 2:
The energy storage capacitor automatically equalizes DC levels across different parts of the switching circuit through its inherent charge storage and transfer properties. This self-service mechanism eliminates the need for complex external DC level shifting circuits, reducing both control complexity and component count while maintaining system compactness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves efficient voltage balancing across battery units, reduces static power consumption, prolongs battery standby time, and is scalable and universal, providing a robust and cost-effective balancing solution for electric vehicles.
Implementation Method 1
an energy storage capacitor network comprising a basic energy storage capacitor network formed by connecting n-1 switch capacitors C1, C2, ..., Cn-1 in series
Data Source
Figure 1a~2c
Figure 3a
Figure 3b
AI summary
A cell balancing device based on a capacitor network, a cascadable balancing battery pack, and a control method thereof, used for battery pack balancing control, and the battery pack being composed of n battery units connected in series; the cell balancing device comprises: n half bridge circuits, each half bridge circuit being connected in parallel to two ends of a battery unit, the midpoint of each half bridge circuit being connected in parallel to a corresponding switch capacitor, and each half bridge circuit comprising two switch transistors connected in series; an energy storage capacitor network, comprising a basic energy storage capacitor network composed of n switch capacitors connected in series; a chain-type driving capacitor network, one end thereof being electrically connected to one of the half bridge circuits or the energy storage capacitor network, and the other end thereof being electrically connected to a drive pulse generator, and the drive pulse generator being electrically connected to the chain drive capacitor network; and a control logic circuit electrically connected to the battery pack, the drive pulse generator, and a master control panel. Using the present solution, the cell balancing device of the present application has excellent balancing effects, reliable performance, strong universality, and strong scalability.