Battery Pack Equalization Timing Under Low-Accuracy Voltage Sensing
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Solution Overview
Problem
Existing battery systems face challenges in accurately determining when equalization control can be ended, especially when the battery is conducting, due to decreased voltage detection accuracy.
Innovation Solution
A battery system that includes a battery pack, an equalizer, and a controller, where the controller determines an equalization time based on resistance of discharge resistors and detection error of voltage sensors, ending the equalization control after this time has elapsed, regardless of voltage detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage detection is used to determine when to end equalization control, then the control can be ended based on voltage equality, but the detection accuracy decreases when the battery is conducting
Solution Approach 1:
The patent changes the control parameter from voltage-based termination to time-based termination. By calculating an equalization time based on battery capacity, current, and equalization current, the system determines when to end equalization control without relying on voltage detection during conduction. This parameter change resolves the contradiction by eliminating the dependency on inaccurate voltage measurements during battery conduction.
2Manufacturing precision
If equalization control is continued until voltage equality is achieved, then thorough equalization is achieved, but the process may be prolonged unnecessarily when detection accuracy is low
Solution Approach 1:
The patent performs preliminary calculation of the equalization time before executing the equalization control. By pre-calculating the required time based on battery capacity, current, and equalization current, the system knows in advance when to terminate the control. This preliminary action prevents unnecessary prolongation of the equalization process while ensuring sufficient equalization is achieved.
Solution Approach 2:
The system uses feedback by continuously monitoring the passage of time during equalization control and comparing it against the pre-calculated equalization time. When the elapsed time reaches the calculated equalization time, the control is terminated. This time-based feedback mechanism ensures precise control duration without relying on inaccurate real-time voltage comparisons during conduction.
3Loss of energy
If the equalization control is ended based on voltage detection, then the process can stop when targets are met, but power may be wastefully consumed if the process continues too long
Solution Approach 1:
The patent changes the termination criterion from voltage-based to time-based. By using pre-calculated equalization time as the termination condition, the system avoids continuous voltage monitoring and detection during conduction. This parameter change eliminates unnecessary energy consumption from prolonged voltage monitoring while ensuring equalization is performed for the appropriate duration.
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 high-accuracy determination of when to end equalization control, preventing unnecessary prolongation of the equalization process and thus conserving power in the battery pack.
Implementation Method 1
a voltage sensor that senses the voltage of each of the plurality of blocks
Implementation Method 2
a plurality of discharge resistors each connected to a respective one of the plurality of switching elements in series
Data Source
AI summary
A battery system comprises a battery pack, an equalization unit, and a battery ECU. The battery pack includes a plurality of blocks connected in series. The equalization unit performs equalization control to equalize the plurality of blocks in voltage. The battery ECU obtains a determined equalization time, and controls the equalization unit to end the equalization control when the equalization time has elapsed since the equalization control was started.