Battery Internal Resistance Measurement Using Periodic Square Wave Excitation
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Solution Overview
Problem
Existing battery internal resistance measurement systems drain significant power from the battery and are time-consuming, making them inefficient for rapid health state assessments.
Innovation Solution
A system comprising a processor, load module, current sense subsystem, multiplexer module, and level shifting, filtering, and amplification subsystem that applies a load to the battery, senses current and voltage changes, filters and amplifies signals to reduce bandwidth, and calculates internal resistance quickly, allowing for faster and less power-intensive measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement systems are used to measure battery internal resistance, then measurement accuracy can be achieved, but the measurement process drains significant power from the battery and takes a long time
Solution Approach 1:
The system applies a periodic square wave current signal to the battery rather than continuous current, allowing the battery to recover between measurement cycles. This periodic excitation reduces cumulative power drain while maintaining measurement accuracy through multiple sampling points across the waveform cycle.
Solution Approach 2:
The system replaces traditional high-current discharge methods with a low-current measurement approach using operational amplifiers and precision voltage sensing. This substitution maintains measurement accuracy while dramatically reducing the power extracted from the battery during testing.
2Measurement precision
If traditional measurement systems are used to measure battery internal resistance, then measurement accuracy can be achieved, but the measurement process is time-consuming
Solution Approach 1:
The system continuously samples voltage across the battery terminals throughout the entire current waveform cycle rather than taking discrete measurements. This continuous monitoring captures the complete voltage response, enabling accurate internal resistance calculation in a single test cycle and eliminating the need for multiple sequential measurements.
Solution Approach 2:
The system pre-charges coupling capacitors and establishes steady-state conditions before applying the measurement current. This preliminary preparation ensures that voltage readings taken during the measurement cycle are not affected by transient charging effects, allowing immediate accurate measurement without extended warm-up or stabilization periods.
3Productivity
If fast measurement is implemented, then measurement speed increases, but measurement precision and resolution deteriorate
Solution Approach 1:
The system introduces operational amplifiers as intermediary devices between the battery voltage and the measurement circuitry. These amplifiers provide high input impedance to minimize loading effects while delivering low-impedance output signals to the ADC, enabling fast sampling rates without sacrificing voltage measurement resolution.
Solution Approach 2:
The system transforms the measurement parameters by measuring voltage drop across a known small resistance value during the current pulse. By changing from measuring absolute battery voltage to measuring differential voltage across a precision resistor, the system achieves both high speed and high resolution in the internal resistance calculation.
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
The system enables rapid and low-drain battery internal resistance measurements, reducing test duration and increasing measurement resolution, thus improving battery health assessment efficiency.
Implementation Method 1
a current sense subsystem for sensing the current flowing to the load module and generating a sensed current signal in accordance therewith
Implementation Method 2
a multiplexer module in communication with the current sense subsystem for detecting voltages across the load module and generating a pair of voltage signals in accordance therewith
Implementation Method 3
filters the voltage signals to reduce a bandwidth of each of the voltage signals, to thus produce reduced bandwidth voltage signals
Implementation Method 4
amplifies the level shifted voltage signals to produce a pair of modified voltage signals
Data Source
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AI summary
In one aspect the present disclosure relates to a system (50) for measuring an internal resistance of a battery. The system may involve: a processor (54); a load module (70) responsive to the processor for applying a load across the battery; a current sense subsystem (72) for sensing the current flowing to the load module and generating a sensed current signal in accordance therewith; a multiplexer module (58) in communication with the current sense subsystem for detecting voltages with the load coupled across the battery and uncoupled from the battery, and generating voltage signals in accordance therewith; and a filtering and amplification subsystem (52) responsive to the multiplexer module, for filtering and amplifying a level of each of the voltage signals to produce modified voltage signals for use by the processor in determining the battery internal resistance.