Vehicle Battery Charging Control With SOC Diagnosis and V2G Switching
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Solution Overview
Problem
Lithium iron phosphate (LFP) battery vehicles face challenges in accurately estimating state of charge (SOC) due to small voltage variations, leading to errors in SOC estimation and limitations on fast charging and output performance.
Innovation Solution
A method of charging a vehicle battery using battery status diagnosis, where a charging controller acquires battery status information, checks accuracy, and determines whether to sell power or perform charging, utilizing vehicle-to-grid (V2G) functionality to improve SOC and state of health (SOH) calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LFP batteries are used in vehicles, then battery safety and stability are improved, but SOC estimation accuracy deteriorates due to small voltage variations
Solution Approach 1:
The patent introduces an OCV correction value as an intermediary element to bridge the gap between measured OCV and actual SOC relationship in LFP batteries. By calculating and applying this correction value, the system compensates for the small voltage variations characteristic of LFP batteries, enabling accurate SOC estimation while maintaining the safety benefits of LFP chemistry
Solution Approach 2:
The patent transforms the SOC estimation approach by changing from direct OCV measurement to a corrected OCV measurement that incorporates temperature compensation and historical data. This parameter transformation allows the system to extract meaningful SOC information from the inherently small voltage variations in LFP batteries
2Measurement precision
If current integration is used for SOC estimation in LFP batteries, then SOC can be estimated, but estimation error increases during flat periods
Solution Approach 1:
The patent implements a feedback mechanism where the OCV correction value is continuously updated based on the difference between measured OCV and expected OCV from current integration. This feedback loop allows the system to learn and compensate for accumulated errors during flat periods, maintaining long-term SOC estimation accuracy
Solution Approach 2:
The patent performs preliminary calibration to establish the OCV-SOC relationship specific to each battery before normal operation. This preliminary action creates a baseline that helps distinguish between normal voltage variations and actual SOC changes, reducing estimation errors during subsequent flat periods
3Reliability
If periodic full discharging is recommended to maintain LFP battery performance, then battery health is improved, but driver convenience deteriorates due to remaining mileage anxiety
Solution Approach 1:
The patent enables the battery management system to automatically perform health-maintaining operations by interpreting corrected SOC data. The system can autonomously initiate charging when SOC reaches optimal levels for battery health, eliminating the need for driver intervention while maintaining both battery health and driving convenience
4Reliability
If fast charging is limited when SOC is uncertain, then battery safety is protected, but charging efficiency deteriorates
Solution Approach 1:
The patent replaces the traditional mechanical/threshold-based charging control system with an intelligent control system based on corrected SOC estimation. By using the accurate corrected SOC values, the system can make informed decisions about fast charging eligibility, replacing conservative threshold-based restrictions with precision-based control that maintains safety while improving charging efficiency
Data Source
AI summary
An embodiment method of charging a battery of a vehicle using battery state diagnosis includes acquiring, by a charging controller, battery status information from the battery, checking, by the charging controller, battery status accuracy using the battery status information, according to the check result, determining, by the charging controller, whether to sell power stored in the vehicle, and according to the determination result, discharging, by the charging controller, the power stored in the vehicle to a charging station or performing charging by receiving power from the charging station.