Battery Cell Equalization During Charging for Faster Balancing
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Solution Overview
Problem
Existing equalization devices for battery packs face challenges in efficiently performing equalization due to prolonged polarization stabilization times, which limits the ability to accurately determine voltage variations and thus extends the equalization time, especially as self-discharge increases with capacity and usage patterns.
Innovation Solution
The equalization device performs equalization discharge not only after polarization cancellation but also during charging and while polarization is occurring, utilizing a state determination unit, charging time variation determination unit, and charging time equalization unit to manage equalization current and voltage measurement accuracy, allowing for prolonged equalization periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equalization is performed only after polarization cancellation, then voltage measurement accuracy is improved, but equalization time is extended
Solution Approach 1:
The patent performs equalization discharge during charging time before polarization cancellation is complete. The control unit starts equalization discharge when the battery pack is in a charging state and stops it when the battery pack reaches a charged state, thereby performing equalization in advance before polarization fully cancels, reducing the overall equalization time while maintaining sufficient voltage measurement accuracy
Solution Approach 2:
The patent dynamically adjusts the equalization discharge current based on the charging state of the battery pack. The control unit controls the equalization discharge current to be a predetermined value during charging, and adjusts it based on state of charge (SOC) differences between cell batteries, optimizing both equalization effectiveness and time efficiency
2Productivity
If equalization discharge current is increased, then equalization speed is improved, but voltage measurement accuracy deteriorates
Solution Approach 1:
The control unit dynamically adjusts the equalization discharge current based on the charging state and SOC differences. During charging, the equalization discharge current is set to a predetermined value that balances speed and accuracy. When SOC differences exceed a threshold, the current is increased to accelerate equalization, otherwise it is reduced to maintain voltage measurement accuracy
Solution Approach 2:
The patent changes the equalization discharge current parameter based on operating conditions. The control unit sets the equalization discharge current to different values depending on whether the battery pack is charging or discharged, and adjusts it based on SOC differences, thereby optimizing both equalization speed and voltage measurement accuracy under different conditions
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 extends the time period for equalization, enhancing the ability to perform equalization (current*time) by managing voltage measurement accuracy and frequency during constant current charging, thereby overcoming limitations in existing technologies.
Implementation Method 1
During charging time of a battery pack, a charging current flows from a positive electrode side to a negative electrode side in each of the cell batteries
Implementation Method 2
voltage across terminals of each of the cell batteries increases by internal resistance*charging current
Implementation Method 3
capacitive components such as a parasitic capacitance are present in parallel with at least part of the internal resistance, and a long time period is required to discharge electric charge stored in the capacitive components
Data Source
AI summary
An equalization device performs equalization of amounts of charge of cell batteries in a battery pack. The device includes a state determination unit that determines whether it is in a predetermined charging state that includes at least one of a state in which the battery pack is subjected to constant current charge and a state in which the battery pack is subjected to constant power charge and does not include a state in which the battery pack is subjected to constant voltage charge, a charging time variation determination unit that determines whether a variation voltage indicating variation of a voltage of each of the cell batteries is higher than a predetermined charging time determination voltage, and a charging time equalization unit that performs the equalization if it is determined that it is in the predetermined charging state and that the variation voltage is higher than the charging time determination voltage.