Pulse Charging Voltage Steps for Fast Battery Charging Heat Control
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Solution Overview
Problem
Conventional charging protocols for electrochemical rechargeable batteries, such as CC-CV, face limitations in increasing charging speed due to thermal heating issues, which can lead to cell aging and reduced performance, making it difficult to achieve charging speeds greater than 2 C-Rate without compromising battery health.
Innovation Solution
A method for rapid charging using pulse control with voltage regulation, where each voltage level is calculated based on the previous level and the variation in internal resistance, allowing for variable amplitude pulses and controlled relaxation phases to manage thermal power and prevent lithium plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant current charging is used to increase charging speed, then charging rate is improved, but cell temperature increases excessively
Solution Approach 1:
The patent applies periodic pulse charging instead of continuous constant current charging. The charging current is delivered in periodic pulses with on-time and off-time intervals, allowing the cell to cool between pulses while maintaining high average charging current. This resolves the contradiction by enabling fast charging without excessive temperature buildup.
Solution Approach 2:
The patent dynamically adjusts the pulse width modulation (PWM) duty cycle based on real-time temperature feedback. When cell temperature increases, the duty cycle is reduced to lower the average charging current and allow cooling. When temperature is acceptable, the duty cycle increases to maintain high charging speed. This dynamic adjustment resolves the contradiction between charging speed and temperature control.
2Reliability
If maximum voltage limit of 4.2V is enforced to prevent lithium plating, then cell safety is improved, but charging voltage cannot be increased for faster charging
Solution Approach 1:
The patent uses periodic pulse charging to temporarily exceed the 4.2V voltage limit during pulse on-time periods, then allows voltage to relax during off-time periods. This periodic over-voltage charging prevents continuous lithium plating while enabling higher average charging power. The relaxation phases allow lithium to redistribute, preventing dendrite formation despite occasional voltage excursions above 4.2V.
Solution Approach 2:
The patent incorporates relaxation phases where charging current is reduced or reversed to counteract the lithium plating tendency created during high-voltage pulse periods. This preliminary anti-action prevents the accumulation of plated lithium that would lead to dendrites and short circuits, allowing the system to safely operate at higher voltages for faster charging.
3Productivity
If pulse charging with relaxed voltage limits is used to increase charging speed, then charging rate is improved, but lithium plating and dendrite formation increase
Solution Approach 1:
The patent implements feedback control by monitoring cell voltage, temperature, and charge capacity during pulse charging. Based on this feedback, the control system dynamically adjusts pulse width, frequency, and duty cycle to prevent lithium plating. When signs of plating are detected, the system reduces pulse amplitude or increases relaxation time, resolving the contradiction between fast charging and preventing harmful lithium deposition.
Solution Approach 2:
The periodic pulse charging with controlled relaxation phases allows the system to temporarily exceed voltage limits for fast charging, then provides regular intervals for lithium to redistribute and prevent plating accumulation. This periodic cycle enables high charging rates while systematically preventing the harmful effects of continuous over-voltage charging.
4Reliability
If constant voltage phase is extended to ensure complete charging, then charging completeness is improved, but overall recharge time increases significantly
Solution Approach 1:
The patent replaces the traditional extended constant voltage phase with periodic pulse charging that maintains higher average voltage and current. The pulse train continues until charge capacity reaches 100%, with the relaxation phases providing sufficient time for voltage equalization and lithium redistribution. This eliminates the prolonged low-current CV phase while ensuring complete charging, significantly reducing total recharge time.
Solution Approach 2:
The patent maintains continuous useful charging action through the pulse train rather than allowing long idle periods at the end of charging. Even as the cell approaches full charge, the periodic pulses continue to deliver charging current during on-time periods, maximizing the utilization of charging time and eliminating the extended waiting period characteristic of conventional CV charging.
Data Source
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AI summary
The present invention relates to a method for charging an electrochemical cell of a rechargeable battery with charging pulse control (PL), the pulses (PL) being driven in voltage control mode in the form of voltage steps (Pt) of variable amplitude. According to the invention, the method consists in calculating the value (Ut+1) of each voltage step (Pt+1) with respect to the value (Ut) of the preceding voltage step (Pt) and according to a progression variable representative of the variation in the internal resistance of the cell (d(R)/dt), for a period ending on the preceding step (Pt), with respect to a predetermined tolerated variation threshold (α), where Var = d(R)/dt - α. The method applies to high-voltage electric battery charging protocols for electromobility or stationary applications, or portable device batteries, for example.