Battery Internal Resistance Calculation for Voltage Stability

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Solution Overview

Problem

Portable device batteries face challenges in maintaining stable voltage due to environmental and temporal factors, leading to potential system shutdowns, especially at non-room temperatures, where inaccurate temperature and state of charge measurements complicate the calculation of internal resistance and maximum allowable current.

Innovation Solution

A battery performance monitoring device with a controller that creates a load pulse to measure voltage and current, calculates internal resistance, and determines a maximum allowable current to prevent voltage drops below a specified threshold, allowing for real-time estimation and adjustment of load currents to prevent shutdowns, even at suboptimal temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the battery operates at non-room temperatures, then the device can function in various environmental conditions, but the voltage stability deteriorates and system shutdowns occur

Engineering Contradiction:

Improveoperational temperature rangeVSAvoidvoltage stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The controller performs preliminary measurements of battery voltage and temperature before operation, and pre-calculates the maximum allowable current based on these conditions. This preliminary action allows the system to adjust operating parameters in advance to prevent voltage instability and shutdowns when operating at non-room temperatures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors battery voltage, temperature, and current draw, and uses this feedback to dynamically adjust the maximum allowable current. When voltage drops are detected or anticipated, the controller reduces the current limit to maintain voltage stability, creating a closed-loop control system that adapts to changing environmental conditions.

Inventive Principle:

Principle #23Feedback

2Power

If the maximum allowable current is increased to improve device performance, then the power output increases, but the voltage drops below the threshold and causes system shutdown

Engineering Contradiction:

Improvemaximum current extractableVSAvoidvoltage threshold maintenance

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The maximum allowable current is not fixed but dynamically adjusted based on real-time battery conditions including temperature, voltage, and state of charge. The controller continuously updates the current limit to optimize power extraction while preventing voltage drops below the threshold, allowing the system to adapt to changing battery characteristics during operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operating parameters (maximum allowable current) based on measured battery conditions. By calculating and adjusting the current limit according to temperature, voltage, and state of charge, the system optimizes power extraction while maintaining voltage stability, resolving the contradiction between maximizing power and preventing shutdowns.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If temperature measurements are used to adjust battery operation, then the system can compensate for environmental effects, but inaccurate temperature measurements lead to incorrect current limits

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidcurrent limit calculation accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system uses multiple measurement parameters (voltage, current, state of charge) as intermediaries to cross-validate and improve the accuracy of temperature-based current limit calculations. By combining multiple sources of information, the system compensates for inaccuracies in individual measurements and achieves more reliable current limit determination.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses feedback from actual battery performance (voltage drops, state of charge changes) to validate and adjust temperature measurements and their interpretation. When measured outcomes diverge from expected results based on temperature alone, the system adjusts its model parameters to improve accuracy, creating a self-correcting measurement system.

Inventive Principle:

Principle #23Feedback

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 solution ensures that portable devices maintain operation by preventing voltage drops below safe levels, enabling graceful shutdowns and protecting the battery, thereby improving user experience and device functionality across varying conditions.

Implementation Method 1

calculate a battery resistance from the measured battery voltage and current

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentUS10509076B2Battery performance monitoring

Publication Date: 2019.12.17 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

In an embodiment, a device comprises a controller configured to create a load pulse for a battery, measure battery voltage concurrently with the load pulse, measure battery current concurrently with the load pulse, calculate a battery resistance from the measured battery voltage and current and based on the battery resistance, calculate a maximum allowable current extractable from the battery, wherein the maximum allowable current is determined such that a voltage across the battery does not drop below a pre-specified threshold voltage when the maximum allowable current is drawn from the battery.