Battery Pack Internal Resistance Testing via Adjustable Resistance
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Solution Overview
Problem
Existing methods for testing the internal resistance of battery packs in electric and hybrid vehicles face limitations, including voltage scope restrictions and potential damage to electrodes, especially when measuring with low current or requiring complex hardware and algorithms.
Innovation Solution
A device and method utilizing an adjustable resistance in a loop circuit with an excitation source and sampling unit to adjust voltage and current, allowing for accurate internal resistance measurement across different voltage scopes without discharging the battery pack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current discharge method is used to measure internal resistance, then measurement can be performed, but the remaining capacity is reduced and electrodes may be damaged due to large current
Solution Approach 1:
The patent uses alternating current injection method instead of direct current discharge, applying periodic AC signals to measure internal resistance without causing continuous capacity loss. The AC injection allows measurement while maintaining battery charge state.
Solution Approach 2:
The patent introduces an adjustable resistance as an intermediary component in the measurement circuit. This resistance divider allows the use of low-current voltage measurements to infer high-current internal resistance characteristics, avoiding direct large current application to the battery.
2Reliability
If alternating current injection method is used, then battery discharge is avoided, but the voltage scope is limited and hardware circuit is complicated
Solution Approach 1:
The patent uses a microcontroller to dynamically adjust the adjustable resistance value based on detected voltage levels. This software-controlled parameter adjustment simplifies the hardware circuit while expanding the measurable voltage scope through adaptive resistance modification.
Solution Approach 2:
The microcontroller serves multiple functions: it controls the adjustable resistance, detects voltage differences, calculates phase differences, and determines internal resistance. This multi-functionality reduces the need for separate dedicated hardware circuits for each measurement function.
3Loss of substance
If low current scope is used for measurement, then battery capacity is preserved, but the battery pack cannot be properly loaded with required large current
Solution Approach 1:
The adjustable resistance acts as a mediator that enables low-current measurement equipment to indirectly measure high-current characteristics. By measuring voltage across the adjustable resistance with low current and calculating the equivalent high-current effect, the system achieves both capacity preservation and measurement capability.
Solution Approach 2:
The system dynamically changes the resistance value to match different voltage scopes and measurement requirements. This parameter adjustment allows the same low-current measurement setup to effectively characterize the battery's high-current behavior through mathematical relationships.
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 enhances measurement accuracy and safety by adjusting the resistance to match the voltage range, reducing the risk of electrode damage and improving the reliability of internal resistance testing across varying voltage conditions.
Implementation Method 1
The alternating current injection method includes adding a constant alternating audio current source to two sides of the battery pack
Implementation Method 2
The internal resistance of the battery pack may be determined according to Ohms' law
Implementation Method 3
an adjustable resistance R located at the circuit formed by the excitation source and the battery pack
Implementation Method 4
detecting the voltage difference between the two sides of the battery pack, and detecting the phase difference therebetween
Data Source
AI summary
An internal resistance testing device includes an excitation source and a battery pack, an adjustable resistance R, a sampling unit, and a control unit. The excitation source and the battery pack form a loop circuit. The adjustable resistance R may be located at the loop circuit formed by the excitation source and the battery pack. The sampling unit samples the voltage between two sides of the battery pack, the voltage between two sides of the adjustable resistance R, and the value of the adjustable resistance R. The control unit calculates internal resistance of the battery pack according to the signal value collected by the sampling unit. The internal resistances of different voltage-ranges the battery pack are determined by adjusting the value of the adjustable resistance R to cause the actual excitation voltage to be equal to the range voltage of the sampling unit. The voltage between two sides of the adjustable resistance R is made equal to the range voltage of the sampling unit by adjusting the value of the adjustable resistance R, which effectively improves measurement accuracy of the internal resistance.