Battery Control System for Low-Temperature Charging
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in charging efficiency at low temperatures due to increased reaction resistance in negative electrode plates, leading to reduced charge capacity and potential metallic lithium deposition during quick charging or regenerative current charging.
Innovation Solution
A battery control system that adjusts the maximum inter-terminal voltage based on the difference in internal resistance between normal and low-temperature ranges, using a product of the difference resistance and allowable charging current to set a suitable voltage, thereby suppressing metallic lithium deposition and maintaining high charge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the maximum inter-terminal voltage is set to a constant value to charge the battery, then the charging control is simple, but the charge capacity is reduced when internal resistance increases due to aging or low temperature
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant voltage charging method to a dynamic charging control method. The maximum inter-terminal voltage is dynamically adjusted based on the detected internal resistance value, allowing the charging system to adapt to changing battery conditions (aging, temperature) and maintain optimal charge capacity without excessive complexity
Solution Approach 2:
The patent implements feedback by continuously detecting the internal resistance of the battery and using this information to adjust the maximum inter-terminal voltage. The charging control device receives feedback about the battery's internal resistance and modifies the charging parameters accordingly, creating a closed-loop control system that optimizes charge capacity
2Productivity
If a high charging current is applied for quick charge or regenerative current charging, then the charging speed is improved, but metallic lithium deposition occurs on the negative electrode plate due to increased polarization
Solution Approach 1:
The patent applies parameter changes by adjusting the maximum inter-terminal voltage based on the product of internal resistance and charging current. When high charging current is applied for quick charging, the system calculates the increased polarization voltage drop and raises the maximum inter-terminal voltage accordingly, preventing metallic lithium deposition while maintaining high charging speed
Solution Approach 2:
The patent implements preliminary action by calculating and setting the appropriate maximum inter-terminal voltage before metallic lithium deposition can occur. The system proactively adjusts the voltage parameter based on detected internal resistance and applied charging current, preventing the harmful effect rather than reacting to it after deposition begins
3Quantity of substance
If the maximum inter-terminal voltage is increased to compensate for internal resistance in deteriorated batteries, then the charge capacity is improved, but the risk of metallic lithium deposition increases due to larger polarization
Solution Approach 1:
The patent uses feedback to precisely control the maximum inter-terminal voltage adjustment. By continuously monitoring the internal resistance and charging current, the system calculates the exact voltage compensation needed (product of internal resistance and charging current) and applies only that amount, avoiding excessive voltage increase that would cause metallic lithium deposition while still improving charge capacity
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the maximum inter-terminal voltage based on the specific combination of internal resistance and charging current conditions. The system modifies the voltage parameter in response to changing battery states, optimizing charge capacity while preventing harmful effects through precise parameter control
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 system effectively charges lithium-ion batteries to a higher inter-terminal voltage while preventing metallic lithium deposition, even at low temperatures, by dynamically adjusting the charging voltage in response to changing internal resistance, thus enhancing charging efficiency and battery capacity.
Implementation Method 1
the larger the value of the internal resistance of the secondary battery is, the higher the inter-terminal voltage becomes. The inter-terminal voltage reaches the maximum value more quickly
Implementation Method 2
at the time of charging, polarization occurs in the negative electrode plate due to the reaction resistance of the negative electrode plate itself. The larger a product of the reaction resistance of the negative electrode plate and the charging current is, the larger this polarization becomes
Data Source
AI summary
A battery control system includes a lithium ion secondary battery and a control device and further includes a voltage storage unit, a resistance storage unit, a current storage unit, a difference obtaining unit for obtaining a difference resistance ΔR(Tja) between a normal internal resistance Rj(Tja) at a predetermined battery temperature Tja in a normal temperature range ATj and an initial internal resistance R0(Tja) at the predetermined battery temperature, and a maximum voltage calculation unit for giving a maximum inter-terminal voltage Vm(T), when at least a battery temperature T is within a low-temperature range ATl, as a value obtained by adding a product of the difference resistance ΔR(Tja) and the allowable charging current Im(T) to the initial maximum inter-terminal voltage Vm0(T).