Battery Discharge Blocking Circuit Corrosion Inhibition
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Solution Overview
Problem
Conventional discharge blocking circuits in battery packs are prone to corrosion due to potential differences between magnesium and nickel alloys when exposed to electrolytes, leading to electrolysis and corrosion, especially under salt fog conditions, and are ineffective at high temperatures or when the thermistor terminal is connected to a magnesium alloy chassis.
Innovation Solution
A discharge blocking circuit is designed with a solid-state data terminal that decouples the control from voltage-sensitive analog thermistor terminals, using a high VGS Field Effect Transistor switch to increase the gate-source threshold, ensuring the circuit is only triggered when the battery is securely docked, thus preventing stray voltages from causing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional discharge blocking circuit uses a thermistor terminal with a low triggering threshold (0.5V), then the discharge blocking feature is activated easily, but the circuit becomes vulnerable to stray voltages from galvanic corrosion between magnesium and nickel alloys, causing false activation and latching the thermistor line to high
Solution Approach 1:
The patent extracts the discharge blocking control function from the thermistor terminal and relocates it to a dedicated data terminal. This separation removes the vulnerability of the thermistor line to galvanic corrosion stray voltages, as the data terminal operates at higher voltage thresholds that are immune to the 1.4V potential difference caused by magnesium-nickel galvanic corrosion.
Solution Approach 2:
The patent introduces a data terminal as an intermediary between the battery management system and the discharge blocking control. This intermediary terminal provides a stable control interface that is not directly exposed to the corrosive electrolyte environment and galvanic potential differences, thereby mediating the control signal away from corrosion-prone pathways.
2Object-affected harmful factors
If the triggering threshold is increased to higher voltages to prevent false activation from stray voltages, then immunity to galvanic corrosion improves, but the discharge blocking circuit becomes ineffective at high temperatures due to lower impedance of the thermistor (negative temperature coefficient)
Solution Approach 1:
The patent extracts the temperature sensing function from the thermistor terminal and places it on a separate thermal terminal. This allows the data terminal to operate at high voltage thresholds for stray voltage immunity while the thermistor independently monitors temperature without being affected by the data terminal's voltage threshold settings.
Solution Approach 2:
The patent segments the battery management functions into separate terminals: the data terminal for discharge blocking control, the thermal terminal for temperature monitoring, and the thermistor terminal for temperature sensing. This segmentation allows each terminal to be optimized for its specific function without compromising the others, enabling high voltage thresholds on the data terminal while maintaining temperature compensation capabilities.
3Object-affected harmful factors
If the thermistor rear charging-interface terminal is relocated away from the magnesium alloy chassis, then corrosion exposure is reduced, but battery miniaturization is impacted and charger pocket design is compromised
Solution Approach 1:
The patent uses the data terminal as an intermediary control point that can be positioned away from the magnesium alloy chassis while still maintaining effective discharge blocking control. This intermediary approach allows the control logic to be separated from the corrosion-prone physical interface, enabling remote positioning of the control terminal without compromising battery compactness or charger integration.
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 solution effectively inhibits corrosion by ensuring the discharge blocking mechanism is immune to low-level stray voltages and only activates when the battery is securely docked, significantly reducing corrosion even in harsh environments like salt water immersion.
Implementation Method 1
using a high VGS Field Effect Transistor switch to increase the gate-source threshold, ensuring the circuit is only triggered when the battery is securely docked
Implementation Method 2
When both metals are electrically connected via an electrolyte, a potential difference of 1.4V forms at the nickel alloy terminals with respect to the magnesium alloy chassis
Data Source
AI summary
A battery pack selectively coupled to a portable electronic device and/or a recharging source, and configured to inhibit corrosion with discharge blocking features, the battery pack includes a positive terminal, a negative terminal, and a data terminal accessible from a housing of the battery pack, wherein each of the positive terminal, the negative terminal, and the data terminal are coupled to a battery in the battery pack; and a discharge blocking circuit configured to allow/block voltage across the positive terminal and the negative terminal based on a presence of a steady state pull up on the data terminal, wherein the steady state pull up is based on the battery pack being coupled to the recharging source, via the positive terminal, the negative terminal, and the data terminal.