Battery Cell Discharge Control via Internal Resistance Estimation
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Solution Overview
Problem
Existing electric storage devices with assembled batteries face challenges in managing individual variability in internal resistance and full charging capacity, leading to potential performance disparities among secondary cells, which can result in uneven battery life and improper functioning when temperature-based capacity control methods fail to account for other influencing factors.
Innovation Solution
The implementation of an electric storage device with internal resistance and full charging capacity estimating means, coupled with discharge quantity calculation and voltage measurement units, allows for the equalization of cell performance by adjusting discharge quantities based on estimated internal resistances and capacities, ensuring balanced operation across multiple cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature-based capacity control is used to manage cell performance, then temperature-related variability is addressed, but individual variability caused by other factors (internal resistance, full charging capacity) is not properly eliminated
Solution Approach 1:
The patent extends the control parameters from only temperature to include internal resistance and full charging capacity. By measuring and adjusting discharge quantities based on these additional parameters, the system comprehensively addresses individual cell variability, ensuring more reliable and consistent cell performance across different influencing factors.
2Reliability
If discharge quantity is adjusted based on internal resistance and full charging capacity, then individual cell variability is eliminated, but measurement and control complexity increases
Solution Approach 1:
The patent employs self-service principles by using the battery management device to automatically measure internal resistance and full charging capacity, calculate appropriate discharge quantities, and control the discharging process without external intervention. This automation reduces operational complexity despite the increased measurement requirements.
Solution Approach 2:
The system implements feedback control by continuously monitoring cell parameters (internal resistance, full charging capacity, temperature) and adjusting discharge quantities accordingly. The battery management device uses this feedback to equalize cell performance, maintaining reliability while managing complexity through closed-loop control.
3Stability of the object's composition
If SOC equalizing function is implemented, then SOC dispersion is maintained within range, but individual variability in internal resistance and full charging capacity still causes performance disparities
Solution Approach 1:
The patent applies preliminary action by measuring and evaluating internal resistance and full charging capacity before the equalizing discharge process. Based on these preliminary measurements, the system calculates and sets appropriate discharge quantities for each cell, preventing performance disparities before they occur rather than merely responding to SOC deviations.
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 effectively equalizes the performance of electric cells, enabling better management and prolonging the lifespan of the assembled battery by addressing variability beyond temperature-related factors, thereby ensuring consistent and efficient energy storage and discharge.
Implementation Method 1
a voltage measurement unit that measures voltages across the plurality of electric cells before a current that flows in the assembled battery is changed, and after the current is changed, in which the internal resistance estimating means estimates the magnitude relationship of the internal resistance from a difference between the voltages across the plurality of electric cells before the current is changed and the voltage across the plurality of electric cells after the current is changed
Implementation Method 2
internal resistance estimating means for estimating internal resistances of the plurality of electric cells or a magnitude relationship of the internal resistances of the plurality of electric cells
Data Source
AI summary
An electric storage device includes an assembled battery including a plurality of electric cells connected in series; an assembled battery control unit that estimates internal resistances of the plurality of electric cells, or a magnitude relationship of the internal resistances of the plurality of electric cells; an assembled battery control unit that calculates such a discharge quantity that an SOC after the electric cells have been discharged becomes lower as the internal resistance of the electric cells, which is estimated by the assembled battery control unit, is larger, or as the magnitude relationship of the internal resistances of the electric cells is estimated to be larger by the assembled battery control unit, for each of the electric cells; and electric cell control units that discharge each of the plurality of electric cells on the basis of the discharge quantity calculated by the assembled battery control unit.