Battery Charging Current Derating Using Voltage Feedback
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Solution Overview
Problem
Existing battery management systems fail to effectively minimize battery cell degradation during charging, as they rely on estimation errors and voltage upper limits, leading to increased charging time and potential further degradation.
Innovation Solution
A battery management system that adjusts the charging current based on a derating factor, which is updated based on the number of periods where the battery pack's voltage exceeds a set voltage upper limit, allowing for dynamic adjustment of charging currents to match the degradation state of the battery cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a typical quick charging algorithm performs charging while reducing the current step by step from a high current to a low current, then charging speed is improved, but battery cell degradation increases due to voltage rise and active material precipitation
Solution Approach 1:
The battery management system implements a feedback mechanism by monitoring the voltage of the battery pack during charging and comparing it with a voltage upper limit value. Based on this feedback, the system dynamically adjusts the charging current using a derating factor that is updated in real-time, allowing the charging process to respond to actual battery conditions rather than following a fixed current reduction schedule
Solution Approach 2:
The patent transforms the static charging current reduction algorithm into a dynamic system where the charging current is continuously adjusted based on real-time voltage measurements. The derating factor is updated during charging cycles based on whether the voltage exceeds the upper limit, creating a dynamic charging profile that adapts to the battery's instantaneous state rather than following a predetermined current schedule
2Duration of action of moving object
If the voltage upper limit is reached and the next step proceeds in the charging algorithm, then charging continues, but the charging time increases compared to the beginning of life (BOL)
Solution Approach 1:
The system uses voltage feedback to determine when to adjust the charging current. By continuously monitoring voltage and comparing it to the upper limit, the system can identify the optimal moment to apply the derating factor, avoiding premature current reduction that would extend charging time unnecessarily while still preventing degradation
Solution Approach 2:
The patent changes the charging current parameter dynamically based on voltage conditions. Instead of reducing current in fixed steps regardless of actual battery state, the system modifies the current parameter only when voltage exceeds the upper limit, optimizing the balance between charging speed and cell protection
3Reliability
If logic charging with SOH reflection is used to lower charging current or capacity, then battery degradation is addressed, but degradation is not completely prevented due to estimation error of the SOH
Solution Approach 1:
The patent introduces voltage as an intermediary parameter between the charging process and SOH estimation. Instead of directly using the imprecise SOH estimation to control charging current, the system uses voltage - a directly measurable and precise parameter - as the primary control variable. The voltage upper limit serves as a reliable threshold that triggers current adjustment, bypassing the need for accurate SOH estimation
Solution Approach 2:
The system replaces the software-based SOH estimation mechanism with a direct voltage measurement and comparison mechanism. By substituting the indirect SOH-based current control with direct voltage-based control, the system achieves more precise and reliable degradation prevention without being constrained by estimation errors
Data Source
AI summary
A battery management system determines a charging current to charge a battery pack in each period based on a derating factor of a charge cycle including a plurality of periods, updates the derating factor based on a result of comparing a voltage of the battery pack in each period with a voltage upper limit value set in the corresponding period, and uses the updated derating factor in a next charging cycle.