Isolated DC/DC Battery Cell Balancing for Aged Series Cells
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Solution Overview
Problem
In high-energy and high-voltage energy storage systems, aged battery cells can lead to uneven charging and discharging, causing over-charging or over-discharging of other cells, potentially damaging them.
Innovation Solution
A battery cell balance circuit with an isolated DC/DC converter and a control unit that adjusts the voltage of aged cells by releasing or supplementing electrical energy, ensuring all cells maintain similar voltages through a network of switches and a circuit switch, connected between an AC/DC converter and the battery cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery cells are connected in series to achieve high-voltage energy storage applications, then the system voltage and energy storage capacity are improved, but voltage imbalance between cells occurs due to aging, leading to over-charging or over-discharging of individual cells
Solution Approach 1:
The patent introduces an isolated DC/DC converter as an intermediary device between the battery cells and the charging/discharging system. This converter acts as a mediator that can independently control the charging and discharging current for each battery cell or group of cells, thereby maintaining voltage balance without requiring direct connection between all cells. The converter includes control circuitry that monitors cell voltages and adjusts power transfer accordingly, preventing over-charging and over-discharging while enabling high-voltage series configuration.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the operating parameters of the isolated DC/DC converter based on real-time battery cell voltage measurements. The control system modifies conversion ratios, switching frequencies, and power transfer rates to compensate for voltage imbalances caused by cell aging. This allows the system to maintain optimal charging/discharging conditions for each cell despite differences in aging states, thereby preserving both high voltage capability and cell balance.
2Productivity
If a single aged battery cell is present in the series connection, then the overall system can still operate, but the aged cell causes rapid voltage changes during charging and discharging, potentially damaging other cells
Solution Approach 1:
The isolated DC/DC converter serves as a protective intermediary that isolates the aged battery cell from the rest of the series connection during charging and discharging operations. The converter's control system detects voltage anomalies from the aged cell and adjusts power flow to prevent harmful voltage spikes or drops from propagating to other healthy cells. This allows the system to continue operating with the aged cell present while protecting other cells from damage.
Solution Approach 2:
The patent implements beforehand cushioning by incorporating voltage monitoring and control mechanisms that anticipate and prevent harmful voltage changes before they can damage other cells. The isolated DC/DC converter continuously monitors cell voltages and pre-adjusts charging/discharging currents to compensate for the presence of aged cells, cushioning against potential voltage instability before it affects the overall system. This proactive approach allows continued operation while preventing damage propagation.
3Reliability
If battery cells are replaced frequently to maintain system performance, then voltage balance and system reliability are improved, but the cost and downtime for maintenance increase
Solution Approach 1:
The patent enables the battery system to self-regulate voltage balance through the isolated DC/DC converter, eliminating the need for frequent manual cell replacements. The converter's control system automatically detects and compensates for voltage imbalances caused by cell aging, allowing the system to maintain reliable operation with the original cell configuration for extended periods. This self-service capability significantly reduces maintenance downtime and costs while preserving voltage balance and system reliability.
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 solution maintains balanced voltages across battery cells during charging and discharging, preventing damage and extending the operational life of the battery module without frequent cell replacements, thus improving economic efficiency.
Implementation Method 1
an isolated DC/DC converter, an input side of the isolated DC/DC converter coupled in parallel to an input side of each of the switches
Data Source
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AI summary
A battery cell balance circuit includes an AC/DC converter (300), a plurality of battery cells (Cell 1-Cell m, Cell 1-Cell 6), a plurality of switches (S1A-SmB, S1-Sm+1, RL1-RL6), an isolated DC/DC converter (400), a circuit switch (SC), and a control unit (500). The AC/DC converter (300) receives an AC power (VAC). The battery cells (Cell 1-Cell m, Cell 1-Cell 6) are connected in series to form a battery link (LCELL). Each switch (S1A-SmB, S1-Sm+1, RL1-RL6) is correspondingly connected to one battery cell (Cell 1-Cell m, Cell 1-Cell 6). The isolated DC/DC converter (400) is coupled to the switches (S1A-SmB, S1-Sm+1, RL1-RL6) and coupled to the battery link (LCELL) in series. The circuit switch (Sc) is coupled between the AC/DC converter (300), the isolated DC/DC converter (400), and the plurality of switches (S1A-SmB, S1-Sm+1, RL1-RL6). The control unit (500) provides a plurality of control signals (SRL1-SRL6, S1c-S7c, SCC) to correspondingly control the plurality of switches (S1A-SmB, S1-Sm+1, RL1-RL6) and the circuit switch (Sc).