Battery Controller Current Variation Estimation
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Solution Overview
Problem
Existing battery monitoring systems fail to consider current variation caused by temperature differences between cells in a parallel battery pack, leading to inadequate protection for cells with higher current flow, even when performing battery protection control based on total or average current.
Innovation Solution
A battery system that includes a controller to estimate current variation by calculating temperature indices for batteries with different heat generation states, using a cooling device to supply a cooling medium and detect temperatures, and setting a temperature additional value based on the heat generating state, allowing for accurate evaluation of temperature and current variation between secondary batteries connected in parallel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If battery protection control is performed based on total current or average current, then the control system is simple, but cells with higher current flow cannot be protected
Solution Approach 1:
The patent segments the total current into individual cell currents by introducing temperature compensation factors for each cell. The controller calculates current for each cell separately based on its temperature, allowing individual cell protection while maintaining a relatively simple overall system architecture.
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to estimate individual cell currents. By measuring temperature and using pre-stored temperature-current correlation data, the system can infer individual cell currents without direct current sensors for each cell, thus protecting cells while keeping the system simple.
2Device complexity
If temperature variation between cells is not considered, then the monitoring system is simple, but current variation between cells cannot be detected
Solution Approach 1:
The patent performs preliminary actions by pre-storing temperature-current correlation data and temperature compensation factors in memory before operation. During runtime, the controller only needs to read the measured temperature and retrieve the corresponding data, enabling accurate current variation detection without complex real-time calculations or additional sensors.
3Measurement precision
If individual cell temperature measurement is implemented, then current variation can be accurately detected, but the system complexity and cost increase
Solution Approach 1:
The patent applies self-service by using the cell's own temperature to determine its current characteristics. Each cell's temperature measurement (or estimated temperature) is used to retrieve its specific compensation factor from stored data, enabling the cell to effectively monitor itself without requiring external intervention or complex centralized control for each cell.
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
Enables accurate estimation of current variation due to temperature differences, thereby implementing appropriate battery protection control, ensuring proper protection for all cells in the battery pack.
Implementation Method 1
a cooling device configured to supply a cooling medium to the battery pack
Implementation Method 2
calculate a first temperature index having correlation with a temperature of the first battery, using an amount of heat generated by the first battery
Data Source
AI summary
An ECU performs a process including the steps of: acquiring a lowest temperature TBmin and a temperature TC of cooling air; acquiring a fan airflow volume; setting a cooling coefficient; calculating a resistance value Rtmin; calculating a root-mean-square value of a current; setting TBoffset1; calculating a resistance value Rtmax; calculating a temperature index Ftmax; calculating a temperature index Ftmin; calculating an evaluation function ΔF; calculating a maximum current correction gain G; and calculating a maximum current value Imax.