Lithium-Polymer Tool Battery Pack for High-Current Compact Power
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Solution Overview
Problem
Existing cordless power tool batteries face challenges in delivering high current and voltage while maintaining compactness and light weight, as traditional batteries often have high internal impedance and limited flexibility in voltage and current output.
Innovation Solution
A lithium-polymer based battery pack with a housing containing multiple flat lithium-polymer battery cells, each with a nominal charged internal impedance of less than 10 milliohms, stacked with a resiliently deformable substrate to accommodate thickness variations and provide a combined output voltage of at least 4 volts and discharge current greater than 10 amps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional battery chemistry is used, then battery pack size and weight increase, but power delivery capability decreases
Solution Approach 1:
The patent changes the chemical parameters of the battery by using lithium-polymer chemistry instead of traditional battery chemistry. This parameter change enables higher energy density and better power delivery characteristics while reducing weight, directly resolving the contradiction between power delivery capability and battery pack weight.
2Quantity of substance
If traditional battery chemistry is used, then battery pack volume increases, but current output capability decreases
Solution Approach 1:
The lithium-polymer chemistry parameter change enables higher current output density per unit volume. The low internal impedance characteristic of lithium-polymer cells allows greater current delivery without proportionally increasing battery pack volume, resolving the contradiction between current output capability and battery pack volume.
3Power
If high current and voltage are delivered, then internal impedance increases, but battery pack compactness decreases
Solution Approach 1:
The patent utilizes the inherent parameter characteristics of lithium-polymer chemistry, specifically its low internal impedance property. This allows the battery to deliver high current and voltage while maintaining stable internal impedance, enabling compact battery pack design without sacrificing power delivery capability.
4Power
If battery cells are stacked to increase power output, then mechanical stability decreases, but power delivery improves
Solution Approach 1:
The patent introduces a resiliently deformable substrate as an intermediary element between stacked battery cells. This substrate accommodates thickness variations and mechanical stresses, maintaining mechanical stability while allowing the cells to be stacked for increased power output, thus resolving the contradiction between combined power output and mechanical stability.
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 lithium-polymer battery pack achieves efficient power delivery with high current and voltage, improved mechanical support, and reduced weight, allowing for more compact designs and increased fill-factor in battery packs, enhancing performance and usability in handheld power tools.
Implementation Method 1
at least one battery cell located within the housing, the cell having an output voltage of at least 4 volts and producing an average discharge current of greater than 10 amps, wherein the battery cell has a lithium-polymer based chemistry
Implementation Method 2
a resiliently deformable substrate located between the adjacent battery cells
Data Source
AI summary
A lithium-polymer based battery pack for power a hand held power tool or a garden tool, the battery pack has a plurality of battery cells located within housing that is selectively connectable to and supportable by a hand held power tool or a garden tool. The battery cells have a lithium-polymer based chemistry and a nominal charged internal impedance of less than or equal to approximately 5 milliohms. In one embodiment the cells are think cells are stacked within the housing such that each sell is layered over or under an adjacent cell and a resiliently deformable substrate located between adjacent battery cells. In another embodiment the cells may be interconnected to have a combined output voltage of at least 9 volts and to produce a combined average discharge current of greater than 20 amps. A lithium-polymer tool battery and a battery powered tool are also part of the invention.