Vehicle Battery Cell Balancing Through Charge Request Control
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Solution Overview
Problem
Energy storage apparatuses in vehicles experience increased differences in electricity amounts between cells due to long charging intervals, leading to inefficient fuel consumption and reduced performance when the state of charge (SOC) is not maintained optimally.
Innovation Solution
An energy storage apparatus connected to a charging device, comprising a plurality of energy storage cells, a balancer circuit, a voltage sensor, and a management unit that requests charging when a predetermined condition is met and adjusts the balancer circuit's operation based on detected voltage differences to reduce electricity disparities between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the energy storage apparatus is charged with electricity supplied from a vehicle generator, then the energy storage apparatus can be charged periodically, but the time interval between charging becomes long when the vehicle is parked, causing increased difference in electric amount between cells
Solution Approach 1:
The management unit performs request processing to request the charging device to charge the energy storage apparatus before the electric amount difference between cells becomes excessive. By anticipating the problem and acting in advance, the system prevents large voltage differences from developing during long parking periods, thereby maintaining cell uniformity without requiring frequent charging.
Solution Approach 2:
The management unit monitors voltages of respective energy storage cells and bases the request processing on detected voltage differences. This feedback mechanism allows the system to adaptively determine when charging is needed, requesting charging when voltage differences indicate that cell imbalance is approaching problematic levels, thus maintaining reliability while optimizing charging intervals.
2Adaptability or versatility
If the SOC is suppressed to around 70% to leave room for regenerative charging, then regenerative energy can be received, but the energy storage apparatus cannot be fully utilized and fuel efficiency deteriorates
Solution Approach 1:
The management unit dynamically adjusts the SOC management strategy based on detected voltage differences between cells. When voltage differences are small, the system allows higher SOC to improve fuel efficiency. When voltage differences increase, the system requests charging to reset the balance, enabling flexible SOC management that adapts to cell conditions rather than rigidly maintaining 70% SOC.
Solution Approach 2:
The system changes the SOC parameter dynamically based on cell voltage differences. Instead of maintaining a fixed SOC around 70%, the management unit adjusts SOC targets and charging requests based on real-time voltage measurements, allowing the SOC to vary within a range that optimizes both fuel efficiency and cell uniformity.
3Reliability
If a balancer circuit is operated to equalize cell voltages, then the difference in electric amount between cells is reduced, but additional circuit complexity is introduced
Solution Approach 1:
The management unit acts as an intermediary that uses simple voltage detection and control logic to achieve cell balancing, replacing the need for complex balancer circuits. By monitoring voltages and requesting charging at appropriate times, the management unit indirectly balances cells through the charging process itself, avoiding the need for direct inter-cell balancing circuits.
Solution Approach 2:
The charging process itself is used to balance the cells rather than requiring a separate balancing mechanism. When the management unit requests charging based on voltage differences, the charging current naturally flows through all cells, equalizing their charge levels. This self-service approach uses the existing charging infrastructure to perform the balancing function.
Data Source
AI summary
An energy storage apparatus 1 that is connected to a vehicle 2 includes: a plurality of energy storage cells 30A; a balancer circuit 38 that makes each of the plurality of energy storage cells 30A individually discharge electricity; a voltage sensor 35 that detects a voltage of each of the energy storage cells 30A; and a management unit 37. The management unit 37 performs: request processing (S103) where the management unit 37 requests the vehicle 2 to charge the energy storage apparatus 1 with electricity when a predetermined condition for reducing a difference in electric amount between the energy storage cells 30A is satisfied; and reducing processing (S106) where, after the energy storage apparatus 1 is charged with electricity by the vehicle 2, a voltage of each of the energy storage cells 30A is detected by the voltage sensor 35, and an operation time of the balancer circuit 38 is changed corresponding to a difference between detected voltages so as to reduce a difference in amount of electricity between the energy storage cells 30A.