Adjustable Voltage Battery Charger for Fast Charging
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Solution Overview
Problem
Existing lithium-ion battery chargers for automotive applications face challenges in reducing charging time while minimizing the impact of fast charging on cycle life, as resistance changes over time due to factors like oxidation of external contacts, leading to increased charging time.
Innovation Solution
A battery charger system employing a continually variable voltage charge-profile that accounts for an imaginary R Bad resistance, which is a function of the battery's state-of-charge, temperature, and nominal resistance, allowing for a multistage charging process with adjustable current and voltage levels to optimize charging rates without degrading battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current and constant voltage charging is used, then battery safety is ensured, but charging time is long (1-5 hours)
Solution Approach 1:
The patent applies dynamics by transitioning from static charging modes (constant current, then constant voltage) to a dynamic charging mode where voltage is continuously adjusted based on real-time measurement of internal resistance. The charger dynamically modifies the voltage profile during charging to maintain optimal charging current, thereby reducing charging time while ensuring safety through continuous monitoring and adaptation.
Solution Approach 2:
The patent implements feedback by measuring the battery's internal resistance during charging and using this information to adjust the charging voltage in real-time. The system continuously monitors the voltage drop across the battery and compensates for changes in internal resistance, creating a closed-loop control system that optimizes charging speed while maintaining safety constraints.
2Productivity
If fast charging is applied to reduce charging time, then charging speed increases, but cycle life degradation occurs due to resistance changes and lithium plating
Solution Approach 1:
The patent applies beforehand cushioning by proactively compensating for internal resistance changes before they cause harmful effects. The system continuously measures and tracks internal resistance variations and adjusts the charging voltage in advance to prevent excessive current that would lead to lithium plating and cycle life degradation, thereby protecting the battery during fast charging.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the charging voltage parameter based on measured internal resistance. Instead of using a fixed voltage profile, the system modifies the voltage parameter in real-time to account for resistance changes due to oxidation and temperature variations, enabling fast charging while maintaining safe operating conditions that preserve cycle life.
3Productivity
If compensation for voltage rise is based on assumed initial resistance, then charging current is maintained during constant current mode, but resistance changes over time due to oxidation leading to increased charging time
Solution Approach 1:
The patent implements feedback by continuously measuring the actual internal resistance during charging rather than relying on assumed initial values. The system uses real-time resistance measurements to adjust the voltage compensation, creating a closed-loop control that maintains accurate charging current throughout the charging process, preventing the charging time increase that occurs with static resistance assumptions.
Solution Approach 2:
The patent applies self-service by enabling the charging system to automatically adapt to its own changing conditions. The charger monitors its own performance and the battery's state, measuring internal resistance changes and adjusting its output accordingly, thereby maintaining optimal charging current without external intervention despite resistance variations caused by oxidation and other factors.
Data Source
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AI summary
A battery cell charger for rapidly charging a lithium ion battery cell (or string of series-parallel connected cells) having a maximum battery cell voltage the battery cell charging system including: a circuit for charging the battery cell using an adjustable voltage charging-profile to apply a charging voltage and a charging current to the battery cell wherein the adjustable voltage charging-profile includes: a first charging stage with a constant first stage charging current and an increasing battery cell voltage with the first stage charging current provided until the first stage charging voltage is about equal to a first stage complete voltage less than the maximum battery cell voltage; one or more intermediate charging stages, each intermediate stage selected from the group consisting of one or more of an intermediate constant voltage stage that provides a decreasing charging current, an intermediate constant current stage that produces an increasing battery cell voltage, and combinations thereof; and a final charging stage with a constant final stage charging voltage about equal to an intermediate stage complete voltage and a decreasing final stage charging current with the final stage charging voltage provided until the final stage charging current reaches a desired charge complete level.