Secondary Battery Output Control for Cell Variation and Over-Discharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing secondary battery output control systems face challenges in accurately detecting temperature variations across all cells due to limited sensor installation, leading to potential over-discharge issues and increased manufacturing costs.
Innovation Solution
A battery output control system that includes cell voltage, current, and temperature detection units, along with a state determination and OCV calculation unit, to dynamically adjust available output power based on cell voltage differences and temperature, preventing over-discharge by switching to minimum cell voltage when variations exceed a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If charge and discharge rates are increased to improve productivity, then output power increases, but heat generation increases causing safety issues and reduced battery life
Solution Approach 1:
The system performs preliminary identification of the battery's thermal state and charge/discharge characteristics before executing high-rate operations. By pre-determining safe operating parameters based on battery state, the system enables high productivity operations while preventing excessive heat generation that would compromise safety or battery life.
Solution Approach 2:
The control system dynamically adjusts charge and discharge rates based on real-time battery state monitoring. When thermal conditions permit, higher rates are allowed for maximum productivity; when temperature rises, rates are automatically reduced to prevent overheating, creating a dynamic balance between productivity and thermal management.
2Device complexity
If output is controlled based on open circuit voltage alone, then device complexity is reduced, but measurement precision and control accuracy deteriorate due to voltage fluctuations during charging/discharging
Solution Approach 1:
The system implements feedback control by continuously monitoring actual battery voltage during charge/discharge operations and comparing it against target values. This feedback mechanism compensates for voltage fluctuations caused by internal resistance, maintaining accurate output control without requiring complex hardware modifications.
Solution Approach 2:
The control method transitions from relying solely on open circuit voltage to using a composite parameter that includes voltage corrections based on charge/discharge rates and battery state. This parameter transformation maintains measurement precision while avoiding the need for complex additional sensing equipment.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An output control method for a secondary battery that obtains available output power that is capable of being output by a secondary battery including a plurality of cells and controls output power of the secondary battery based on the available output power is provided. The output control method include: an indication amount calculation step of calculating a variation indication amount that correlates with a magnitude of variation between charge and discharge characteristics of the plurality of cells, based on a charge and discharge characteristic indication amount that changes according to change in the charge and discharge characteristic; a determination step of determining that the variation occurs when the variation indication amount is equal to or larger than a predetermined determination reference value; and an available output power setting step of setting the available output power based on a determination result that the variation occurs. In the available output power setting step, when the variation does not occur, a basic available output power determined based on the charge and discharge characteristic indication amount is set as the available output power. When the variation occurs, a corrected available output power having a value lower than that of the basic available output power is set as the available output power.