Electric Tool Battery Reverse Charging Prevention

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Solution Overview

Problem

When battery packs with different voltages are connected in parallel, reverse charging can occur, affecting the efficiency of the power supply in lawn and garden power tools, as current from the higher voltage battery flows into the lower voltage battery, leading to inefficiencies.

Innovation Solution

A power tool design that includes a controller to detect voltage drops across switch devices and control the electrical connections between battery packs and the motor, using field effect transistors to manage the connections and prevent reverse charging by disconnecting the battery pack with a lower voltage when the voltage drop is below a certain threshold, ensuring that only the battery pack with a higher voltage powers the tool.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If battery packs with different voltages are connected in parallel to increase power capacity, then the power supply capacity is improved, but reverse charging occurs causing energy loss and reduced efficiency

Engineering Contradiction:

Improvepower supply capacityVSAvoidenergy loss from reverse charging

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent introduces switch devices as intermediaries between battery packs and the motor. These switches act as controllable gates that prevent direct uncontrolled current flow between battery packs of different voltages, thereby eliminating reverse charging while maintaining the ability to connect multiple battery packs for increased power capacity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The controller continuously monitors voltage levels of individual battery packs and uses this feedback information to control the switch devices. When a voltage difference exceeding a threshold is detected, the controller activates the appropriate switches to prevent reverse charging, ensuring efficient power supply while maintaining battery pack integrity.

Inventive Principle:

Principle #23Feedback

2Reliability

If switch devices are added to control battery connections, then reverse charging is prevented, but device complexity increases

Engineering Contradiction:

Improveprevention of reverse chargingVSAvoidcomplexity from additional switch devices

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses voltage threshold parameters to control switch device operation. By monitoring whether voltage differences exceed a predetermined threshold, the system simplifies control logic while maintaining reliability in preventing reverse charging, balancing complexity and effectiveness.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If voltage monitoring and control is implemented, then power supply efficiency is improved, but measurement and control difficulty increases

Engineering Contradiction:

Improvepower supply efficiencyVSAvoiddifficulty in voltage monitoring and control

Core Design Contradiction:

ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The controller monitors voltage parameters of battery packs and compares them against predetermined thresholds. This parameter-based control approach simplifies the detection and measurement process while maintaining high power supply efficiency, making the system manageable despite the added monitoring requirements.

Inventive Principle:

Principle #35Parameter changes

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 effectively prevents reverse charging and ensures efficient power supply by ensuring that only the battery pack with a higher voltage powers the tool, maintaining efficiency and preventing over-discharge, thus enhancing the performance and longevity of the power tool.

Implementation Method 1

detect a first voltage drop across the first switch device from a respective high potential point to a respective low potential point

Methodology Applied

Scientific EffectVoltage drop detection: Ohm's Law

Implementation Method 2

the first switch device is a field effect transistor

Methodology Applied

Scientific EffectField effect transistor switching:

Data Source

PatentEP3288147B1Electric tool and control method therefor

Publication Date: 2020.05.06 NANJING CHERVON IND

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AI summary

A power tool capable of being balance powered by multiple battery packs is provided. A power tool comprising: a motor; a first battery pack; a second battery pack; a first battery receptacle for receipt of the first battery pack; a second battery receptacle for receipt of the second battery pack; a first switch device for connecting to the first battery pack and the motor; a second switch device for connecting to the second battery pack and the motor; and a controller operable tosend a signal to cause the switch device opened so as to disconnect the battery pack and the motorwhen the voltage of the switch device is less than a control voltage.