Li-Ion Battery Pack Charge Equalization via Inductive Transfer
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Solution Overview
Problem
Lithium-ion battery packs suffer from nonuniformity in voltage, current, and charge/discharge time due to variations in individual cells, leading to reduced efficiency and lifespan, especially in larger packs, as existing charge equalization methods are inefficient, energy-consuming, and unable to handle high currents or ensure real-time balancing.
Innovation Solution
A basic unit of a lithium-ion battery pack comprising series-connected cells, a balancing cell, controllable switches, a drive module, and a controller for real-time charge/discharge equalization, using contactless matrix switches and MOSFETs to manage voltage and current sharing between cells, ensuring uniform charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If energy consumption type equalizing method is used with shunt resistance, then charge equalizing is achieved, but energy is consumed and large amount of heat is produced
Solution Approach 1:
The patent introduces an inductance as an intermediary energy transfer carrier between lithium-ion cells. Instead of directly dissipating excess energy through resistance, the inductance temporarily stores energy from cells with higher charge and transfers it to cells with lower charge, achieving equalization without energy loss or heat generation.
Solution Approach 2:
The patent replaces the resistive equalizing mechanism (energy consumption type) with an inductive energy transfer mechanism (non-energy consumption type). This substitution eliminates the harmful thermal effects and energy waste associated with shunt resistance while maintaining the equalizing function.
2Reliability
If energy consumption type equalizing method is used, then charge equalizing is achieved, but control is complicated and high currents cannot be equalized
Solution Approach 1:
The inductance serves as a mediator that simplifies the equalizing process. By using the inductance to transfer energy between cells, the system avoids complex control algorithms required for resistive equalizing, enabling straightforward control even at high current levels.
3Loss of energy
If non-energy consumption type equalizing method with inductance is used, then energy transfer is achieved, but control system is complicated and large-sized inductances occupy large space
Solution Approach 1:
The patent combines multiple functions into a single integrated circuit board structure that houses both the inductances and the control electronics. This merging eliminates the need for separate large-sized inductance components, reducing overall space occupation while maintaining energy conservation benefits.
Solution Approach 2:
The patent embeds the inductances within the battery pack structure itself, nesting them among the lithium-ion cells. This nested arrangement utilizes available space efficiently, minimizing the external footprint while preserving the energy transfer capability.
4Power
If lithium-ion cells are connected in series to increase capacity, then voltage increases, but voltage difference between cells increases and lifespan decreases
Solution Approach 1:
The inductance acts as a real-time mediator that continuously balances voltage differences between series-connected cells. By transferring energy from higher-voltage cells to lower-voltage cells, the inductance prevents excessive voltage divergence that would otherwise occur in series configurations, thereby extending pack lifespan.
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 enables safer, efficient, and stable energy balancing during both charge and discharge, allowing for higher current equalization, improved accuracy, and extended battery life by maintaining uniform voltage across cells, thus overcoming the limitations of existing methods and enabling larger capacity packs.
Implementation Method 1
a balancing lithium-ion cell connected in parallel to the lithium-ion cells; controllable switches controlling independently a connection in parallel between the balancing lithium-ion cell and each of the lithium-ion cells
Implementation Method 2
The controllable switches are contactless matrix switches. Each contactless matrix switch comprises a forward matrix switch connected between the anode of the lithium-ion cell and the anode of balancing lithium-ion cell and a backward matrix switch connected between the cathode of the lithium-ion cell and the cathode of balancing lithium-ion cell
Implementation Method 3
a voltage detection module for detecting a voltage at two ends of the lithium-ion cells
Data Source
AI summary
A lithium-ion battery includes two or more series-connected lithium-ion cells, a balancing lithium-ion cell, controllable switches with the same number as the lithium-ion cells, a drive module for the controllable switches, a voltage detection module for detecting a voltage at two ends of the lithium-ion cells, and a controller. The balancing lithium-ion cell is connected in parallel to the lithium-ion cells. The controllable switches control the turn on/off of the connection in parallel between the balancing lithium-ion cell and each of the lithium-ion cells independently. The drive module for the controllable switches and the voltage detection module are connected to the controller. A battery pack including the lithium-ion battery and a method for real-time charge/discharge equalizing of the lithium-ion battery are also provided.