Cell Balancing Circuitry for Battery Packs
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Solution Overview
Problem
Existing battery pack technologies face inefficiencies in balancing the state of charge and voltage across cells, leading to uneven charging and discharging, which can result in reduced battery life and energy waste, particularly in applications like electric vehicles where uniform cell performance is critical.
Innovation Solution
The implementation of switched capacitor or inductor based cell balancing circuitry that transfers energy between cells to equalize their state of charge and voltage, using a network of switches and capacitors or inductors to manage energy distribution efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If passive cell balancing is used to equalize cell voltage, then cell voltage uniformity is improved, but energy is wasted as heat and battery life is reduced
Solution Approach 1:
A DC-DC converter is introduced as an intermediary device between cells to transfer energy from higher voltage cells to lower voltage cells. This mediator enables active balancing by converting and redirecting energy rather than dissipating it as heat, thus maintaining cell voltage uniformity while preserving energy.
Solution Approach 2:
The system changes the operating parameters of cell balancing by transitioning from passive resistance-based equalization to active DC-DC converted energy transfer. This parameter change enables energy recovery and redistribution, converting wasted thermal energy into useful electrical energy for charging lower voltage cells.
2Duration of action of stationary object
If cell balancing circuitry is added to equalize cell performance, then battery life is extended, but device complexity increases
Solution Approach 1:
The DC-DC converter is designed to perform multiple functions: it balances cell voltages during charging, recovers energy from higher voltage cells, and charges lower voltage cells simultaneously. This multi-functionality reduces the need for separate balancing circuits and simplifies the overall system architecture.
Solution Approach 2:
Instead of discarding excess energy from higher voltage cells as heat, the system recovers this energy through the DC-DC converter and redistributes it to lower voltage cells. This recovery approach extends battery life by utilizing otherwise wasted energy while avoiding the need for complex passive balancing networks.
3Reliability
If charging is stopped early to protect the weakest cell, then cell reliability is improved, but productivity is reduced
Solution Approach 1:
The DC-DC converter acts as a mediator that enables continued charging of the battery pack even when individual cells reach their voltage limits. By transferring energy from charged cells to uncharged cells, it allows the system to exceed the charging capacity of the weakest cell without compromising its reliability.
Solution Approach 2:
The system performs preliminary energy transfer between cells during charging, equalizing cell voltages before the weakest cell reaches its maximum capacity. This preliminary action prevents the need to stop charging early, thereby maintaining both cell reliability and charging productivity.
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
This approach enhances battery pack efficiency by reducing energy waste, extending the battery life and maintaining consistent performance across cells, thereby improving the range and reliability of electric vehicles.
Implementation Method 1
a capacitor, wherein the switch network is controllable such that: in a first phase of operation of the switched capacitor based cell balancing circuitry, the capacitor is coupled in parallel with a cell of the first module; and in a second phase of operation of the switched capacitor based cell balancing circuitry, the capacitor is coupled in parallel with a different cell of the first module or with a cell of the second module
Data Source
AI summary
Balancing circuitry for balancing cells in first and second modules of a battery pack, wherein the first module comprises a first plurality of cells and the second module comprises a second plurality of cells, the balancing circuitry comprising: first cell balancing circuitry operative to balance the first plurality of cells of the first module; and second cell balancing circuitry operative to balance the second plurality of cells of the second module, wherein the second cell balancing circuitry is further operative to balance at least one cell of the first plurality of cells of the first module with at least one cell of the second plurality of cells of the second module.