Battery System Reverse Current Polarization Cancellation
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Solution Overview
Problem
Lithium ion battery cells with silicon negative electrodes experience prolonged polarization elimination times, leading to decreased accuracy in State Of Charge (SOC) estimation due to prolonged deviation from Open Circuit Voltage (OCV) after charging-discharging, especially at low temperatures or in degraded states.
Innovation Solution
A battery system that includes a voltage measurer and a controller to apply a reverse current after charging-discharging to cancel polarization voltage, shortening the time for convergence to OCV and improving SOC estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium ion battery cell uses a negative electrode material mixed with silicon, then the battery capacity is improved, but the polarization elimination time becomes excessively long (1 hour to 10 hours or more)
Solution Approach 1:
The patent applies a preliminary counteracting action by introducing a reverse current in the opposite direction to the charging current immediately after charging completion. This reverse current actively counteracts the polarization voltage buildup, preventing the prolonged deviation from OCV that would otherwise occur with silicon-based negative electrodes. The reverse current magnitude is controlled to be less than the charging current magnitude, creating a balanced correction that accelerates polarization elimination without causing excessive charging.
2Quantity of substance
If the polarization elimination time is long, then the battery can maintain high capacity, but the SOC estimation accuracy decreases due to prolonged deviation from OCV
Solution Approach 1:
By applying a reverse current that counteracts polarization voltage immediately after charging, the patent enables early and accurate OCV measurement. This preliminary correction action allows SOC estimation to be performed with high accuracy right after charging completion, rather than waiting for prolonged polarization elimination periods.
3Device complexity
If no reverse current is applied, then the battery system is simple, but the time required for polarization elimination becomes excessively long
Solution Approach 1:
The patent utilizes the battery management system's existing current control capability to generate and apply the reverse current. The same controller that manages charging operations also controls the post-charging reverse current application, allowing the system to serve its own polarization elimination need without requiring separate dedicated hardware components. This self-service approach accelerates polarization elimination while maintaining system simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables highly accurate OCV estimation at an early stage post-charging/discharge, enhancing SOC estimation precision and reducing the time required for polarization elimination.
Implementation Method 1
the controller performs control to apply a reverse current for canceling the polarization voltage of the battery cell through the battery cell after the completion of charging-discharging of the battery cell
Data Source
AI summary
A voltage measurer measures a voltage of a battery cell. A controller controls charging-discharging of the battery cell. The controller performs control to apply a reverse current for canceling a polarization voltage of the battery cell through the battery cell after the completion of charging-discharging of the battery cell. For example, after the charging-discharging of the battery cell completes, the controller sets a current command value, in a power converter, that instructs flow of a reverse current of a preset value for a preset time.