Battery Electrode Potential Control for Overcharge Prevention
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Solution Overview
Problem
Lithium ion batteries used in various applications deteriorate with repeated charge/discharge cycles, leading to reduced capacity and increased charging time, and existing control methods do not accurately estimate battery deterioration, risking overcharge or overdischarge.
Innovation Solution
A battery control device and method that estimates the potential of a lithium ion battery's positive and negative electrodes by acquiring an open circuit voltage curve, allowing for dynamic adjustment of charge and discharge cut-off voltages to prevent deterioration, using a charge/discharge controller, open circuit voltage curve acquisition device, and arithmetic processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge/discharge control is implemented by gradually lowering charge cut-off voltage and increasing discharge cut-off voltage when cycle count exceeds a threshold, then battery safety is improved, but manufacturing precision deteriorates because the method does not estimate actual battery deterioration and may adjust voltages more than necessary
Solution Approach 1:
The patent changes the parameter for determining charge/discharge cut-off from a simple cycle count threshold to dynamically calculated electrode potentials derived from open circuit voltage curves. By measuring the actual open circuit voltage and calculating positive and negative electrode potentials, the system adjusts charge cut-off voltage and discharge cut-off voltage based on real battery state rather than predetermined cycle numbers, achieving precise control adapted to actual deterioration
Solution Approach 2:
The patent replaces the mechanical counting method (cycle-based control) with an electrochemical measurement system that calculates electrode potentials from open circuit voltage curves. This substitution enables precise estimation of battery deterioration state and allows for accurate adjustment of voltage limits based on actual electrode conditions rather than rough cycle thresholds
2Device complexity
If fixed charge/discharge control is used without deterioration estimation, then device complexity is reduced, but reliability deteriorates due to risk of overcharge and overdischarge
Solution Approach 1:
The patent implements self-service by using the battery's own open circuit voltage characteristics to estimate its deterioration state. The system measures the open circuit voltage curve inherent to the battery and calculates electrode potentials from this self-generated data, eliminating the need for external complex testing equipment while achieving accurate deterioration estimation and adaptive voltage control
3Measurement precision
If open circuit voltage curve measurement is performed to estimate electrode potentials, then measurement precision is improved, but loss of time increases due to charging/discharging required for measurement
Solution Approach 1:
The patent achieves multi-functionality by using the open circuit voltage curve measurement for dual purposes: (1) estimating battery deterioration through electrode potential calculation, and (2) determining appropriate charge/discharge cut-off voltages. This single measurement process serves multiple functions, reducing the need for separate testing procedures and minimizing time loss while maintaining high measurement precision
Data Source
AI summary
The battery control device includes: a charge/discharge controller configured to charge or discharge the secondary battery during diagnosis; an open circuit voltage curve acquisition device configured to acquire an open circuit voltage by charging or discharging the secondary battery; and an arithmetic processor configured to estimate a potential of the positive electrode and a potential of the negative electrode from an open circuit voltage curve. The battery control device controls the charge cut-off voltage and the discharge cut-off voltage such that an estimated positive potential does not exceed an upper limit and a lower limit of voltage that are preset.