Battery Unit Switching Internal Resistance for NiCd Charger Compatibility
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Solution Overview
Problem
Cadmium-based batteries, such as NiCd, are environmentally harmful and costly to replace, as existing charging devices for these batteries are not compatible with cadmium-free alternatives like lithium cells, which require different charging methods and can be damaged by constant current charging devices.
Innovation Solution
A battery unit with a switch unit that alters its internal resistance based on charging voltage, allowing it to mimic the behavior of NiCd batteries and safely interrupt charging when the end-of-charge voltage is reached, using existing NiCd charging devices without modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cadmium-based batteries are replaced with cadmium-free lithium cells, then environmental safety is improved, but compatibility with existing charging devices deteriorates
Solution Approach 1:
A switch unit is introduced as an intermediary component between the lithium cell and the charging device. This switch unit modifies the voltage profile during charging to simulate NiCd battery behavior, enabling compatibility with existing NiCd charging devices while using environmentally safe lithium cells. The switch unit acts as a mediator that translates between the different charging requirements of lithium cells and NiCd charging devices.
Solution Approach 2:
The switch unit dynamically changes electrical parameters (voltage and resistance) during the charging process. By adjusting these parameters to match the characteristic voltage profile of NiCd batteries, the system enables lithium cells to be charged using NiCd charging devices without modification. This parameter transformation resolves the incompatibility between different battery chemistries and their charging requirements.
2Productivity
If constant current charging is used for lithium cells, then charging speed is improved, but battery safety deteriorates due to overcharging
Solution Approach 1:
The switch unit implements a feedback mechanism that continuously monitors the charging voltage and cell state. When the end-of-charge voltage is detected, the switch unit activates to modify the voltage profile, preventing overcharging. This feedback control allows the system to maintain fast charging speeds while automatically preventing dangerous overcharging conditions that would occur with unmodified constant current charging.
Solution Approach 2:
The switch unit is pre-configured with knowledge of the lithium cell's end-of-charge voltage characteristics. Before overcharging can occur, the switch unit anticipates the voltage threshold and activates protective measures by modifying the voltage profile. This preliminary anti-action prevents the harmful effect of overcharging while maintaining the benefits of constant current charging throughout most of the charging cycle.
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
Enables the replacement of NiCd batteries with lithium cells in existing charging systems, preventing damage to lithium cells by simulating the voltage profile of NiCd batteries and ensuring safe termination of the charging process, thus avoiding the need for new charging devices and ensuring environmental safety.
Implementation Method 1
the internal resistance of the battery unit is altered depending on the charging voltage of the battery cell
Data Source
AI summary
A rechargeable battery unit and method for charging a battery is provided. The battery unit can be connected to a constant current charging device for charging the battery unit. The constant current charging device has a plurality of poles and a cut-off voltage. The battery unit has an internal resistance, a lithium battery cell having a predetermined end-of-charge voltage, and a switch unit. The switch unit is configured to enable alteration of the internal resistance when the predetermined end-of-charge voltage has been reached, such that the voltage at the poles of the constant current charging device is greater than the cut-off voltage of the constant current charging device to terminate the charging process.