Battery Pack Control Circuit for Cordless Power Tools
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Solution Overview
Problem
Conventional battery packs for cordless power tools face challenges with higher voltage requirements, leading to increased weight and potential motor damage due to higher currents, necessitating additional protection controls against over-charge, over-discharge, over-current, and other fault conditions.
Innovation Solution
A battery pack with an integrated electronic control circuit and additional protection circuits to manage and limit currents, detect stall conditions, and provide over-voltage protection, ensuring safe operation and preventing damage to the tool and battery pack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional NiCd or NiMH battery packs are used to provide higher voltage outputs (18V or higher), then the power output is sufficient for cordless power tools, but the overall weight of the battery pack becomes prohibitively heavy
Solution Approach 1:
The patent applies parameter changes by transitioning from NiCd/NiMH chemistry to Li-ion chemistry, which fundamentally changes the electrochemical parameters of the battery system. Li-ion batteries provide higher energy density and lower weight for the same power output, directly resolving the contradiction between sufficient power and reduced weight
2Weight of moving object
If Li-ion batteries are used to reduce battery pack weight and increase capacity, then the weight is reduced and capacity per unit volume increases, but the batteries require over-discharge protection to prevent rapid deterioration
Solution Approach 1:
The patent implements preliminary action by incorporating protection circuits that proactively monitor and prevent over-discharge conditions before they can damage the Li-ion batteries. The control circuit continuously monitors cell voltage and prevents discharge below safe thresholds, ensuring battery durability while maintaining the weight and capacity benefits of Li-ion technology
3Power
If battery packs with lower impedance characteristics are used to provide higher current output, then the power delivery capability increases, but demagnetization forces in the motor increase beyond design limits causing potential motor damage
Solution Approach 1:
The patent applies feedback by implementing control circuits that continuously monitor motor current and provide feedback to the battery management system. When current levels approach thresholds that could cause demagnetization, the system automatically adjusts or limits current output, allowing high power delivery capability while protecting the motor from damage
4Object-affected harmful factors
If additional protection controls are implemented to prevent motor damage from high current, then motor safety is improved, but the device complexity increases
Solution Approach 1:
The patent applies merging by integrating protection functions into the existing battery management and control circuits rather than adding completely separate protection systems. The same microcontroller and sensing infrastructure used for battery management is leveraged to provide motor protection, reducing overall system complexity while maintaining comprehensive protection capabilities
Data Source
AI summary
A battery pack which includes a battery pack electronic control circuit adapted to control an attached power tool and/or an attached charger. The battery pack includes additional protection circuits, methodologies and devices to protect against fault conditions within the pack, as the pack is operatively attached to and providing power to the power tool, and/or as the pack is operatively attached to and being charged by the charger.