Battery Pack Full-Charge Detection from Charging Current Drop
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Solution Overview
Problem
The increase in the number of terminals on chargers and battery packs due to separate communication lines for charge complete indication complicates wiring and increases component count.
Innovation Solution
A battery pack with current measurement means and a control circuit determines full charge based on the reduction rate of charging current, eliminating the need for a separate communication line by matching the charge complete indication with the charger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate communication line is provided between the charger and battery pack to transmit charge complete indication, then the battery pack can match its charge complete indication with the charger, but the number of terminals on both the charger and battery pack increases, complicating wiring and increasing component count
Solution Approach 1:
The patent merges the charge complete indication function into the existing charging current line. The battery pack's control circuit detects the charger's charge complete status by monitoring changes in the charging current (specifically, when the charging current drops to a predetermined value or below), eliminating the need for a separate communication line. This combines the power transmission function and information transmission function into a single line, reducing terminal count and wiring complexity while maintaining reliable charge complete indication matching between charger and battery pack.
2Loss of information
If a separate communication line is provided for charge complete indication, then accurate charge complete matching is achieved, but the terminal count and component count increase
Solution Approach 1:
The charging current line is given dual functionality: it serves both as the power transmission path and as the information transmission path for charge complete indication. The control circuit in the battery pack monitors the charging current to detect when the charger has determined charge complete (by detecting when current drops to a predetermined value). This multi-functional use of the existing line eliminates the need for additional terminals and components while ensuring accurate charge complete information transmission and matching between charger and battery pack.
Data Source
AI summary
A battery pack is provided in which the battery pack itself can recognize a determination of a full charge, which is made by a charger, without using a communication line. A battery pack is provided with a secondary battery, current measurement means for measuring a charging current for charging the secondary battery, and a control circuit which receives an output signal from the current measurement means. The control circuit determines that the secondary battery is fully charged when a reduction rate of the charging current in a unit time exceeds a predetermined value.