Alternating Discharge Charge Battery Charging Profile
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Solution Overview
Problem
Traditional charging methods for electric vehicle batteries, especially high-voltage lithium-ion batteries, face challenges in achieving fast charging without compromising battery longevity due to high C-rates, which lead to lithium plating, self-heating, and impedance increases, and also struggle to balance fast charging with increasing energy density.
Innovation Solution
A charging profile that alternates between a brief discharge stage at constant power and a subsequent charge stage at constant current, repeated until the battery is fully charged, which improves cycle life and coulombic efficiency by reducing concentration gradient and polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional constant current charging is used to achieve fast charging, then charging speed is improved, but battery longevity deteriorates due to lithium plating, self-heating, and impedance increases
Solution Approach 1:
The patent applies periodic action by alternating between discharge pulses and charge phases. During discharge pulses, the battery is briefly discharged at constant power, then charged at constant current. This periodic alternation prevents continuous high C-rate charging that causes lithium plating and self-heating, thereby maintaining battery longevity while achieving fast charging overall.
Solution Approach 2:
The patent changes the charging parameters dynamically by switching between constant power discharge and constant current charge modes. The discharge power is set to a specific range (25-1000 kW) and the charge current is controlled to achieve optimal charging rates. This parameter optimization allows fast charging without exceeding thresholds that would harm battery longevity.
2Loss of time
If high C-rates are used for fast charging, then charging time is reduced, but harmful factors increase including lithium plating, self-heating, and impedance increases
Solution Approach 1:
The patent converts the potential harm of high C-rate charging into benefit by using brief discharge pulses. These discharge pulses temporarily increase current flow but in a controlled manner that actually reduces concentration gradients and polarization, thereby preventing the harmful effects of continuous high-rate charging while still achieving fast overall charging.
Solution Approach 2:
By periodically interrupting the charging process with discharge pulses, the system prevents continuous harmful high C-rate charging. The discharge phases occur at specific intervals, allowing the battery to briefly reverse polarity and reduce lithium plating and self-heating accumulation, thus eliminating harmful factors while maintaining fast charging capability.
3Quantity of substance
If energy density is increased to improve battery capacity, then battery longevity is improved, but fast charging capability deteriorates
Solution Approach 1:
The patent applies dynamics by making the charging process adaptive rather than static. The charging profile dynamically switches between discharge and charge phases based on real-time battery conditions. This dynamic approach allows high energy density batteries to accept fast charging by adjusting the charging rate through periodic discharge pulses, preventing the trade-off between energy density and fast charging capability.
Data Source
AI summary
A method for charging a traction battery of an electric vehicle includes, in response to a request to charge a traction battery, initially discharging the traction battery, for a first duration of time, according to a discharge stage having a constant power; subsequently charging the traction battery, for a second duration of time, according to a charge stage having a constant current; and repeating the discharge stage and the charge stage in sequence until the battery is charged.