Battery Charger Controller Scheduling for Capacity Degradation
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Solution Overview
Problem
Rechargeable batteries for portable electronic devices face degradation due to the formation of deposits during charging, which increases internal resistance and reduces their capacity, as they are often kept at or near full charge, leading to faster capacity degradation.
Innovation Solution
A battery charger controller determines a total charge time based on the battery's state of charge, time constant, and full charge capacity, delaying charging until a predetermined start time to minimize time at full charge, switching between constant current and constant voltage charging states to maintain and increase the battery's state of charge efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the battery is charged continuously to maintain full charge capacity, then the battery's ability to deliver current deteriorates due to deposit formation and increased internal resistance
Solution Approach 1:
The battery charging system implements periodic charging cycles with distinct phases: a first charging phase at higher current to rapidly replenish charge capacity, followed by a second charging phase at lower current to top off the battery. This periodic variation in charging current prevents continuous high-current stress that causes deposit formation, while still maintaining full charge capacity over time.
Solution Approach 2:
The charging system dynamically adjusts the charging current based on the battery's state of charge and time since last charge. The controller transitions between different charging phases (first phase with higher current, second phase with lower current) to optimize both charge capacity replenishment and minimize internal resistance increase. This dynamic adjustment resolves the contradiction by adapting charging parameters to current battery conditions.
2Ease of operation
If the battery is kept at full charge state for extended periods, then the battery capacity degrades faster, but the device is ready for immediate use
Solution Approach 1:
The battery charging system performs preliminary charging actions during off-peak periods or when the device is not in use. The controller charges the battery to full capacity in advance, then maintains it in an optimal charge state rather than continuously at 100%. This preliminary action ensures device readiness when needed while avoiding prolonged exposure to full charge conditions that accelerate degradation.
Solution Approach 2:
The system dynamically manages battery charge state based on usage patterns and time. After initial charging to full capacity, the controller transitions to maintenance charging modes that keep the battery ready for use without maintaining continuous full charge. This dynamic charge management extends battery lifespan while preserving ease of operation.
3Loss of time
If fast charging is applied continuously, then the charging time is reduced, but the battery internal resistance increases due to deposit formation
Solution Approach 1:
The charging system applies fast charging (first charging phase) periodically rather than continuously. The controller switches between a first charging phase with higher current for rapid charge replenishment and a second charging phase with lower current to complete the charging process. This periodic alternation reduces overall charging time while minimizing the cumulative effect of high-current stress that causes deposit formation and internal resistance increase.
Solution Approach 2:
The charging system changes charging parameters (current level, charging phase) based on battery state and time. The controller adjusts the charging current between two distinct levels, transitioning from fast charging to slower top-off charging. This parameter change optimizes the balance between charging speed and battery health, reducing internal resistance increase while maintaining acceptable charging times.
Data Source
AI summary
A battery charger can include a charger controller configured to determine a total charge time that characterizes a time needed to charge a battery, the total charge time being based on a received state of charge (SOC) of the battery that characterizes a present SOC of the battery. The charger controller can also be configured to determine a charging start time for the battery based on a predetermined full charge time and the total charge time.