Dynamic Charge Current Control for Battery Degradation
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Solution Overview
Problem
Existing lithium-ion secondary battery charging methods face a trade-off between reducing charge duration and suppressing charge/discharge cycle degradation, as increasing charge current shortens the charge duration but accelerates degradation, while decreasing it prolongs the duration but reduces battery life.
Innovation Solution
A charging system that dynamically adjusts the charge current by switching from a higher first charge current to a lower second charge current based on the state of charge and inter-terminal voltage, and further adjusts these values in response to battery degradation, using a control unit to manage the charger and optimize charge duration and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the charge current is increased to reduce charge duration, then the charge duration is shortened, but the charge/discharge cycle degradation increases and service life is reduced
Solution Approach 1:
The patent applies dynamics by making the charge current adjustable rather than fixed. The control unit dynamically changes the charge current based on the battery's state of charge and degradation level. During early charging stages, a higher current is used to reduce charging time, while later stages use lower current to minimize degradation, thereby resolving the contradiction between charge duration and service life
Solution Approach 2:
The patent changes the charge current parameter based on charging progress and battery condition. By adjusting the charge current from high to low as charging progresses, and further reducing it when degradation is detected, the system optimizes both charge speed and battery longevity, addressing the trade-off between charge duration and service life
2Reliability
If the charge current is decreased to suppress charge/discharge cycle degradation, then the service life is extended, but the charge duration increases
Solution Approach 1:
The system dynamically adjusts charge current based on real-time battery status. Instead of using a consistently low current, the control unit starts with higher current to minimize charging time, then transitions to lower current as the battery approaches full charge or when degradation is detected, thus extending service life without unnecessarily prolonging charge duration
Solution Approach 2:
The patent implements periodic monitoring of battery parameters (state of charge, temperature, degradation level) and adjusts charge current accordingly. This periodic assessment allows the system to switch between different current levels, achieving both fast charging when appropriate and degradation suppression when necessary
Data Source
AI summary
A charging system includes battery pack and charger. During the charge of secondary battery, charge control unit controls charger so that the charger performs constant-current charge at a first charge current, and, when at least one of the following conditions is satisfied, switches the first charge current to a second charge current lower than the first charge current and continues the constant-current charge. The conditions include the condition that the SOC of secondary battery arrives at a threshold SOC value and the condition that the inter-terminal voltage of secondary battery arrives at a threshold inter-terminal voltage. In response to the degree of degradation of secondary battery, the charge control unit drops at least one of the threshold SOC value and the threshold inter-terminal voltage.