Multi-cell Battery Balancing via Charge Quantity Alignment
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Solution Overview
Problem
Existing battery balancing methods require batteries to be taken offline for an extended period, which is undesirable in industries requiring sustained power output, as they focus on equating cell voltages rather than charge quantities, leading to inefficiencies and prolonged downtime.
Innovation Solution
A method and system for balancing multi-cell batteries by determining alignment distances based on current charge quantities to adjust and equalize charge quantities across cells, allowing for balancing while the battery is in operation, thereby reducing the need for extensive offline balancing and minimizing state of charge/charge quantity variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional voltage-based balancing method is used, then cell voltage equality is achieved, but battery must be taken offline for extended period (25 hours loss of time)
Solution Approach 1:
The patent changes the balancing parameter from voltage to charge quantity (coulomb counting). By monitoring and equalizing the charge quantity passed through each cell rather than equalizing voltage, the system achieves balancing without requiring the battery to be taken offline, thus resolving the contradiction between achieving cell equality and minimizing downtime
Solution Approach 2:
The patent replaces the traditional mechanical/voltage-based balancing approach with an electrical measurement approach using coulomb counters. This substitution allows continuous monitoring and balancing during operation, eliminating the need to stop the battery system for balancing operations
2Extent of automation
If continuous voltage monitoring is performed during operation, then real-time balancing control is possible, but voltage readings become misleading due to internal resistance effects
Solution Approach 1:
The patent changes the measurement parameter from voltage to charge quantity (current integration). By measuring and integrating current over time through coulomb counters rather than measuring voltage, the system avoids the measurement errors caused by internal resistance and overpotential effects that occur during operation
Solution Approach 2:
The patent introduces coulomb counters as intermediary devices that measure current and integrate it to determine charge quantity. These counters serve as mediators between the battery cells and the control system, providing accurate charge quantity measurements without being affected by voltage fluctuations or internal resistance effects
3Reliability
If balancing is performed to equalize cell voltages, then voltage balance is achieved, but charge quantity variance remains significant leading to reduced effective capacity
Solution Approach 1:
The patent changes the balancing objective from voltage equality to charge quantity equality. By using coulomb counters to track and equalize the charge quantity passed through each cell, the system directly addresses charge quantity variance rather than voltage variance, thereby maximizing effective battery capacity
Solution Approach 2:
The patent implements feedback control by continuously monitoring charge quantity through coulomb counters and using this information to control the balancing process. The system adjusts charging/discharging based on charge quantity measurements, creating a closed-loop control system that ensures accurate charge equalization
Data Source
AI summary
There is described a method of balancing a multi-cell battery. An alignment distance for each cell of the multi-cell battery is determined. The alignment distance defines a change in charge quantity required to achieve a target alignment point, based on a current charge quantity of the cell. Based on the determined alignment distances, one or more unbalanced cells are identified. Each unbalanced cell is then balanced by adjusting its current charge quantity according to the alignment distances. In one embodiment, the target alignment point is a target state of charge. In another embodiment, the target alignment point is a target charge quantity.