Battery Cell Balancing Control for Idle Voltage Drift
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Solution Overview
Problem
Energy storage apparatuses with multiple lithium ion secondary batteries face challenges in maintaining equal voltages due to differences in self-discharging electricity amounts, leading to voltage inequalities that conventional balancer circuits struggle to address, especially when the system is left idle for extended periods.
Innovation Solution
An energy storage apparatus with a balancer circuit and management unit that performs specific processing to reduce voltage differences by discharging energy storage cells based on historical discharge data, even when the initial conditions for discharge are not met, and adjusts discharging amounts based on past discharge histories to maintain balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional balancer circuit is used to reduce voltage differences between energy storage cells, then voltage balance is improved during active operation, but voltage inequalities reaccumulate when the system is left idle for extended periods
Solution Approach 1:
The management unit performs preliminary discharging action on energy storage cells with higher self-discharge rates before voltage inequality becomes significant. By proactively equalizing cells during idle periods based on historical discharge data, the system prevents voltage imbalance from accumulating, thereby extending the time before balancer circuit intervention is needed and maintaining reliability over longer idle periods
2Reliability
If the balancer circuit continuously monitors and discharges cells to maintain voltage equality, then voltage balance is maintained, but energy is wasted through continuous discharging operations
Solution Approach 1:
The management unit utilizes feedback from historical discharge data and self-discharge characteristics of each cell to intelligently determine when and how much to discharge. By analyzing past discharge patterns and predicting future voltage drift, the system performs targeted discharging only when necessary, minimizing energy waste while maintaining voltage balance. The feedback mechanism allows the system to learn from previous operations and optimize discharge decisions
Solution Approach 2:
The system changes the discharge parameter (discharge amount and timing) based on each cell's specific self-discharge characteristics and historical data. Instead of uniform continuous discharging, the management unit dynamically adjusts discharge parameters to match actual cell needs, reducing unnecessary energy loss while maintaining voltage equality
3Loss of energy
If no discharging control is performed during idle periods, then energy is conserved, but voltage inequalities between cells increase significantly over time
Solution Approach 1:
The management unit enables the balancer circuit to perform self-service discharging operations during idle periods based on automated analysis of cell voltages and historical discharge data. The system autonomously determines which cells need discharging and by how much, without requiring external intervention or continuous monitoring, thereby maintaining voltage balance while minimizing energy consumption through targeted rather than continuous operation
Data Source
AI summary
In an energy storage apparatus 1, first reducing processing where, in a case where a voltage of any one of the energy storage cells 30A is increased or a difference in voltage between any of the energy storage cells 30A is increased so that a first condition is satisfied, the difference in a remaining electricity amount between the energy storage cells 30A is reduced; second reducing processing where the difference in remaining electricity amount between the energy storage cells 30A is reduced in a case where the second condition of reducing a difference in a remaining electricity amount between the energy storage cells 30A is satisfied during a period that the first condition is not satisfied; and decision processing where a balancer discharging electricity amount when the energy storage cell 30A is discharged by the second reducing processing is decided based on a discharging history when the energy storage cell 30A is discharged by at least the first reducing processing are performed.