Battery Equalization via Extended Discharge Time
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Olivine-type lithium-ion iron secondary batteries face challenges in equalizing capacities due to a plateau region where voltage remains constant, making it difficult to estimate remaining capacity, and a variation region where voltage sharply increases, leading to incomplete charging and discharging.
Innovation Solution
An electric storage device management apparatus and method that monitors voltage and current during charging and discharging, using a CPU to control a discharging circuit to discharge batteries based on measured time periods and equalization discharging currents, ensuring all batteries reach a reference voltage before terminating the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage information is used to estimate capacity in the plateau region, then capacity estimation is attempted, but the estimation becomes inaccurate because voltage remains constant despite SOC changes
Solution Approach 1:
The patent changes the operational parameter from the plateau region to the variation region where voltage changes with SOC. By performing capacity equalization in the variation region instead of the plateau region, the system achieves accurate voltage-based capacity estimation while effectively equalizing battery capacities.
2Productivity
If discharging is performed based on voltage information in the variation region, then capacity equalization is attempted, but charging ends before equalization is complete because voltage sharply increases with small SOC changes
Solution Approach 1:
The patent applies preliminary action by extending the discharging time period beyond the conventional charging duration. The control unit determines a discharging time period that is longer than the charging time period, ensuring that capacity equalization is completed even in the variation region where voltage changes sharply.
Solution Approach 2:
The patent maintains continuous useful action by extending the discharging process beyond the point where charging would normally terminate. The discharging circuit continues to operate until the predetermined discharging time period elapses, ensuring complete capacity equalization rather than stopping when charging ends.
3Productivity
If conventional discharging time is used for capacity equalization, then the process completes within standard charging duration, but capacity equalization is insufficient because discharging ends upon charging termination
Solution Approach 1:
The system preliminarily determines an extended discharging time period that exceeds the charging duration. This predetermined time period is stored and used to ensure sufficient equalization time is allocated, addressing the insufficiency of conventional equalization timing.
Solution Approach 2:
The discharging operation continues uninterrupted beyond the charging termination point. The control unit maintains the discharging circuit operation for the full predetermined discharging time period, ensuring continuous capacity equalization without premature termination.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electric storage device management apparatus(20) is provided for monitoring an electric storage device assembly(12) charged and discharged by a charger/discharger(18). The electric storage assembly(12) includes a plurality of electric storage devices(50) connected in series. The electric storage device management apparatus(20) includes a voltmeter(24), a discharging circuit(26), and a controller(30). The voltmeter(24) is configured to measure voltages of the electric storage devices(50) respectively. The discharging circuit(26) is configured to discharge the electric storage devices(50) individually. The controller(30) is configured to: determine whether a voltage of each electric storage device(50) has reached a reference voltage during charging or discharging of the electric storage device assembly(12); and control the discharging circuit to discharge each electric storage device(50) if the voltage of the electric storage device(50) has reached the reference voltage.