Probabilistic Multi-Cell Balancing for Battery Charge Homogeneity
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Solution Overview
Problem
Multi-cell batteries do not charge and discharge evenly due to variations in cell strength, leading to overcharging and over-depletion of weaker cells, which limits their utilization and battery life.
Innovation Solution
A battery management system that uses probabilistic selection to balance battery cells by measuring currents and voltages, estimating states of charge, and adjusting charges based on deviation from the mean state of charge, allowing for real-time balancing during charging, discharging, or at rest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If passive battery balancing is used to balance battery cells, then battery cell charge differences are reduced, but charge is drawn from the weakest battery cells causing them to age quickly and decreasing discharge depth
Solution Approach 1:
The patent changes the balancing parameter from fixed passive discharge to adaptive active transfer. The system dynamically adjusts which cells receive charge and which donate charge based on real-time state of charge measurements, cell selection probabilities, and balancing needs, transforming the balancing process from a static parameter to a dynamic adaptive parameter.
Solution Approach 2:
Instead of drawing charge from weaker cells as in passive balancing, the patent inverts the approach by transferring charge to weaker cells from stronger cells. This reversal prevents further aging of weak cells while still achieving charge balance, resolving the contradiction between balancing and battery life preservation.
2Stability of the object's composition
If active balancing transfers charge from higher energy cells to lower energy cells based on state of charge deviation, then battery cell balance is improved, but the maximum charge transfer rate limits balancing effectiveness during maximum charging and discharging
Solution Approach 1:
The patent implements periodic probabilistic cell selection where the system continuously monitors battery cells and performs balancing operations at periodic intervals during charging and discharging. The probabilistic selection mechanism creates a dynamic periodic action pattern that adapts to real-time battery conditions, allowing effective balancing even during maximum charge/discharge cycles.
Solution Approach 2:
The patent transforms the static charge transfer rate into a dynamic system by continuously adjusting cell selection probabilities based on real-time state of charge measurements. The balancing rate becomes adaptive rather than fixed, allowing the system to maximize balancing effectiveness within the physical charge transfer limits during varying charge/discharge conditions.
3Measurement precision
If battery cells are selected for balancing according to the difference between each cell's state of charge and the mean state of charge, then balancing targets the most unbalanced cells, but the maximum charge transfer rate results in cells remaining unbalanced during maximum charging and discharging
Solution Approach 1:
The patent changes the selection parameter from deterministic (always selecting the cell with maximum deviation) to probabilistic (selecting cells based on probability proportional to deviation). This parameter transformation allows the system to distribute balancing efforts across multiple cells over time, achieving reliable balancing even when individual charge transfer rates are limited during maximum charging and discharging.
Data Source
AI summary
A computer-implemented system and method for balancing battery cells of a multi-cell battery, the system comprising a processor configured to determine a state of charge for each battery cell, generate a probability table for all of the battery cells based on a difference between the state of charge for each battery and a mean state of charge, select one of the battery cells via probabilistic selection according to the probability table, and generate an instruction for adjusting a charge of the selected battery cell.