HV Battery Equalization Charge Control Strategy

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Solution Overview

Problem

Fuel cell vehicle batteries experience unequal state of charge among cells due to internal resistance and aging, requiring manual service center charging for equalization, which is inconvenient and disrupts vehicle use.

Innovation Solution

A system and method that monitors battery cell state of charge and current, adjusts the charge current limit, and converts it to a power charge limit to overcharge the battery while driving, ensuring all cells are fully charged and equalized using a small current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the battery is charged with a special charging device at a service center to equalize cell state of charge, then all cells become fully charged and equalized, but the vehicle cannot be driven during service and must be taken to the service center

Engineering Contradiction:

Improvebattery cell state of charge equalizationVSAvoidvehicle usability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The battery equalization process is performed automatically by the vehicle's own power management system during normal operation. The system monitors individual cell states and automatically directs charging current to cells that need equalization, eliminating the need for external service center intervention and allowing continuous vehicle use.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system performs equalization charging proactively during periods when the battery state indicates a need for equalization, rather than waiting for service center intervention. By detecting SOC disparities early and addressing them during normal operation, the system prevents the condition that would require service center attention.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the battery charge current is increased to speed up equalization, then equalization time is reduced, but cells may become overheated and damaged

Engineering Contradiction:

Improveequalization speedVSAvoidcell overheating and damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Instead of applying uniform charging current to all cells, the system identifies individual cells with lower state of charge and directs charging current specifically to those cells. This localized approach allows faster equalization of disadvantaged cells without subjecting already-charged cells to excessive current that would cause overheating.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system continuously monitors the state of charge of individual battery cells and uses this feedback information to dynamically adjust charging current distribution. When a cell approaches full charge, the system reduces or stops current to that cell while redirecting current to cells that still need charging, preventing overheating while maintaining equalization speed.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If the battery charge current is limited to a small amount to prevent overheating, then cell safety is maintained, but equalization time increases

Engineering Contradiction:

Improvecell overheating preventionVSAvoidequalization duration

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The system applies different charging current levels to different cells based on their individual state of charge. Cells that are significantly behind in charge receive higher current (within safe limits), while cells that are nearly full receive reduced or no current. This localized current distribution accelerates equalization without causing overheating in any individual cell.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The charging current to each cell is dynamically adjusted based on real-time monitoring of cell state of charge and temperature. As cells approach equalization or full charge, the system automatically modulates current levels, allowing higher currents during early equalization phases and reducing currents as cells near completion, optimizing both speed and safety.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8148952B2Control strategy for HV battery equalization charge during driving operation in fuel cell hybrid vehicles

Publication Date: 2012.04.03 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A system and method for equalizing the state of charge of the cells of a battery in an electric vehicle while the vehicle is being driven. The method includes monitoring the state of charge of the battery cells in the battery and measuring the actual current of the battery. The method also includes determining a maximum charge current limit of the battery and comparing the actual battery current and the charge current limit. The method also includes modifying the charge current limit based on the comparison between the actual battery current and the charge current limit. The method then converts the modified charge current limit to a power charge limit and then over charges the battery using a small amount of current and the power charge limit so that all of the cells in the battery become fully charged.