Nickel-Metal Hydride Cell State of Charge Adjustment for Rapid Degradation Detection
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Solution Overview
Problem
Existing methods for manufacturing battery packs are inefficient due to the inability to quickly distinguish between cells or battery modules that have truly degraded and those that can be recovered, leading to prolonged inspection times and reduced production efficiency.
Innovation Solution
A method involving the adjustment of the state of charge of nickel-metal hydride battery cells or modules to specific ranges (0-3%, 3-20%, or 100-200%) to measure voltage lowering, combined with temperature monitoring during charging, to rapidly identify defective products and recover apparent degradation, thereby enhancing detection accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long time is spent for inspection to distinguish between cells with apparent performance lowering and truly degraded cells, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The patent changes the parameter of state of charge to extreme values (0-3% or 100-200%) to amplify the difference in voltage lowering between good cells and truly degraded cells. This parameter change enables rapid detection within 1 hour instead of requiring long-term observation, thus resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The patent performs preliminary charging or discharging to adjust the state of charge to extreme ranges before measurement. This preliminary action prepares the cells in a state where the voltage lowering characteristic is maximized, enabling quick and accurate differentiation without requiring extended inspection time
2Ease of operation
If simple open circuit voltage measurement is used for screening, then ease of operation is improved, but measurement precision deteriorates due to inability to distinguish apparent performance lowering from true degradation
Solution Approach 1:
The patent changes the state of charge parameter to extreme ranges (0-3% or 100-200%) before measurement. This parameter change causes truly degraded cells to exhibit significantly different voltage lowering characteristics compared to cells with apparent performance lowering, thereby improving measurement precision while maintaining the simplicity of voltage measurement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the efficient detection of truly degraded cells in a short period, reducing the time required to differentiate between good and defective products, thereby streamlining the battery pack manufacturing process and potentially recovering cells with apparent degradation.
Implementation Method 1
If the cell etc. is a nickel-metal hydride battery, such apparent lowering in performance particularly tends to occur due to self-discharge.
Implementation Method 2
A cell etc. of which performance has apparently lowered can be recovered, for example, by performing full-range charging and discharging.
Data Source
AI summary
(A) A used battery pack is prepared. (B) By disassembling the used battery pack, a cell etc. is collected from the used battery pack. The cell etc. are a nickel-metal hydride battery. (C) A state of charge of the collected cell etc. is adjusted to a state of charge within any of a first SOC range (0 to 3%), a second SOC range (3 to 20%), and a third SOC range (100 to 200%). (G) An amount of voltage lowering as a result of the cell etc. being left is calculated. (H) When the amount of voltage lowering is equal to or smaller than a reference value set in advance, the cell etc. is determined as a good product. (I) A battery pack including the cell etc. determined as the good product is manufactured.