Vehicle Battery Stack Balancing via Sequential Cell Interruption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Battery systems in vehicles face inefficiencies due to unbalanced state of charge (SOC) among battery cells, leading to premature discharge and potential damage, as existing balancing methods are not fully effective in maximizing the use of the battery's potential capacity.
Innovation Solution
A method that identifies the battery cell with the lowest or highest SOC in a set of battery stacks, temporarily interrupts its discharge or charge, and sequentially manages the discharge or charge of other cells to balance the SOC levels, using a control unit to monitor and adjust based on system characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery cells are charged or discharged based on the weakest cell's capacity, then the battery system's reliability is improved, but the productivity deteriorates as only 60-90% of the battery stack's full potential can be utilized
Solution Approach 1:
The battery system is segmented into multiple independent battery stacks, each with its own set of battery cells connected in series. This segmentation allows individual stacks to be managed separately, enabling the system to identify and address unbalanced cells in specific stacks without affecting the entire battery system. The control unit can selectively charge or discharge individual stacks based on their specific cell balance status.
Solution Approach 2:
The control unit performs preliminary identification of unbalanced battery cells by monitoring the state of charge of each cell in every stack before initiating charge or discharge operations. This preliminary assessment allows the system to pre-determine which stacks need balancing and adjust the charge/discharge strategy accordingly, preventing the weakest cell from limiting the overall system performance.
2Device complexity
If battery cells with different capacities are connected in the same stack, then the device complexity is reduced, but the reliability deteriorates as unbalanced cells lead to over discharge and potential permanent damage
Solution Approach 1:
By dividing the battery system into multiple stacks, the patent isolates unbalanced cells to specific stacks rather than affecting the entire system. This segmentation allows the system to maintain a simple overall structure while implementing targeted balancing strategies for individual stacks with unbalanced cells.
Solution Approach 2:
The control unit applies local quality management by identifying stacks with unbalanced cells and applying specific charge or discharge rates to those particular stacks. This localized approach allows different parts of the battery system to operate with different characteristics - balanced stacks can operate at full capacity while unbalanced stacks receive adjusted treatment.
3Reliability
If traditional balancing methods like resistive balancing are used, then the reliability of individual cells is improved, but the loss of energy increases as energy is dissipated as heat through resistors
Solution Approach 1:
The patent extracts the unbalanced battery cells from the overall charge/discharge path by identifying and isolating specific stacks with unbalanced cells. These extracted stacks are then managed separately through selective connection or disconnection from the main charge/discharge circuit, allowing the balanced stacks to operate efficiently without being constrained by the unbalanced cells.
Solution Approach 2:
The system dynamically adjusts the charge and discharge rates for individual battery stacks based on their real-time cell balance status. The control unit continuously monitors and modifies the operational parameters of each stack, enabling flexible adaptation to changing battery conditions without requiring passive energy dissipation methods.
Data Source
AI summary
A method of controlling a battery system in a vehicle during discharging or charging includes temporarily interrupting discharging or charging of the identified battery cell with the lowest or highest state charge level; continuing discharging or charging the remaining battery cells; sequentially temporarily interrupting discharging or charging a battery cell in each one of the other battery stacks; controlling a duration of the sequentially temporarily interrupting discharging or charging a battery cell in each one of the other battery stacks based on a battery system characteristic; comparing a monitored state charge levels of the remaining battery cells with the state charge level of the lowest or highest battery cell of the corresponding battery stack; and resuming discharging or charging of the identified battery cell when state charge levels of the remaining battery cells of the set of battery cells corresponds to the state charge level of the identified battery cell.