Power Tool Battery Discharge Control via Temperature Feedback

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Solution Overview

Problem

Rechargeable batteries in power tools often overheat due to internal resistance, leading to premature shutdown before they are fully discharged, resulting in unused capacity.

Innovation Solution

Implementing open-loop and closed-loop control methods that monitor temperature and voltage, adjusting current intensity to prevent overheating by reducing power output when thresholds are reached, allowing for more efficient use of battery capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the power tool operates at high current intensity to maximize power output, then productivity and power are improved, but the rechargeable battery overheats prematurely and shuts down before full discharge

Engineering Contradiction:

Improvepower outputVSAvoidbattery temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The control device dynamically adjusts the current intensity based on real-time temperature feedback from the battery. When the battery temperature approaches the critical threshold, the control device automatically reduces the current intensity to prevent overheating, allowing the battery to discharge more completely without premature shutdown

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A temperature sensor continuously monitors the battery temperature and feeds this information back to the control device. The control device uses this feedback to adjust the current intensity accordingly, creating a closed-loop control system that prevents overheating while maximizing battery capacity utilization

Inventive Principle:

Principle #23Feedback

2Temperature

If the power tool reduces current intensity to prevent battery overheating, then battery temperature is controlled, but productivity and power output decrease

Engineering Contradiction:

Improvebattery temperatureVSAvoidpower output

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The control device periodically monitors battery temperature and adjusts current intensity in cycles. During normal operation, high current intensity is maintained for maximum productivity. When temperature approaches the critical threshold, current intensity is reduced temporarily until the battery cools down, then restored to high levels, creating a periodic adjustment pattern that balances productivity and temperature control

Inventive Principle:

Principle #19Periodic action

3Reliability

If the power tool uses simple temperature-based shutdown to ensure safety, then reliability is improved, but battery capacity utilization deteriorates due to premature shutdown

Engineering Contradiction:

ImprovesafetyVSAvoidbattery capacity utilization

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Instead of a simple on/off shutdown, the control device implements continuous temperature monitoring with feedback control. When the battery temperature approaches but has not yet reached the critical threshold, the control device proactively reduces current intensity to prevent overheating. This allows the battery to be used much closer to its full capacity while maintaining safety

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control device takes preliminary action by reducing current intensity before the battery temperature reaches the critical shutdown threshold. This preventive approach allows the battery to discharge nearly completely without triggering premature safety shutdown, significantly improving capacity utilization while maintaining reliability

Inventive Principle:

Principle #10Preliminary action

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

Ensures the effective use of battery capacity by slowing down temperature rise, allowing the battery to be discharged almost completely before shutdown, thereby optimizing energy utilization.

Implementation Method 1

recording at least one temperature value of the rechargeable battery by a temperature measuring device

Methodology Applied

Scientific EffectTemperature measurement:

Implementation Method 2

recording at least one first voltage value of the rechargeable battery by a voltage measuring device

Methodology Applied

Scientific EffectVoltage measurement:

Implementation Method 3

the rechargeable battery is heated up by the internal resistance (also referred to as the output resistance) of the rechargeable battery cells when the electrical energy is delivered

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS20220344960A1Method for the efficient discharge of a rechargeable battery

Publication Date: 2022.10.27 HILTI AG

AI summary

A method for the open-loop and closed-loop control of a power tool with at least one rechargeable battery, a drive and at least one control device, the rechargeable battery serving as an energy supply for the power tool. The method includes the method steps of: recording at least one temperature value of the rechargeable battery by a temperature measuring device; recording at least one first voltage value of the rechargeable battery by a voltage measuring device; and setting a first performance parameter value of the power tool to a second performance parameter value of the power tool for setting a current intensity value if the recorded temperature value corresponds to a predetermined temperature threshold value and the recorded voltage value corresponds to a predetermined voltage threshold value. A system including a power tool and at least one rechargeable battery for supplying the power tool with electrical energy for carrying out the method.