EV Battery Capacity Measurement Through V2G Charge-Discharge Cycling

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Solution Overview

Problem

Existing electric vehicles face challenges in accurately determining battery capacity due to aging and inaccurate battery state of charge (SOC) estimation, necessitating periodic full discharge and charge cycles, which can be inefficient and potentially harmful to the battery.

Innovation Solution

Implementing a vehicle-to-grid (V2G) discharge and charge cycling operation through a connected charging station, allowing the vehicle to control discharge and charge cycles electronically, measuring energy transfer to accurately determine battery capacity and recalibrate SOC estimation systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a full discharge and charge cycle is performed to accurately measure battery capacity, then measurement precision is improved, but productivity deteriorates due to the time-consuming nature of the process

Engineering Contradiction:

Improvebattery capacity measurement accuracyVSAvoidcycle operation speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent introduces a power consumption device as an intermediary component to enable controlled discharge of the battery. This device acts as a mediator between the battery and the measurement system, allowing for standardized discharge conditions that improve measurement consistency while maintaining operational efficiency. The power consumption device provides a controlled load that enables accurate capacity measurement without requiring complete battery depletion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a full discharge cycle is performed to determine true battery capacity, then measurement precision is improved, but object-affected harmful factors worsen due to potential battery degradation

Engineering Contradiction:

Improvebattery capacity measurement accuracyVSAvoidbattery degradation

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies partial action by performing discharge cycles that do not necessarily deplete the battery to complete exhaustion. Instead, the system performs controlled discharge operations using the power consumption device to gather sufficient measurement data without subjecting the battery to the stress of full depletion. This approach obtains accurate capacity information while minimizing harmful effects on battery health.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system incorporates feedback mechanisms that monitor battery state during discharge operations. By continuously measuring voltage, current, and other parameters during the controlled discharge process, the system can adjust the discharge rate and duration to prevent excessive stress on the battery. This feedback control ensures accurate measurement while protecting the battery from degradation.

Inventive Principle:

Principle #23Feedback

3Reliability

If periodic battery capacity measurement is performed to account for aging effects, then reliability is improved, but loss of time increases due to the frequency of required measurements

Engineering Contradiction:

Improvebattery capacity information accuracyVSAvoidmeasurement operation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements periodic action by establishing scheduled intervals for battery capacity measurements. Rather than requiring continuous monitoring or frequent complete discharge cycles, the system performs measurements at predetermined intervals using the power consumption device. This periodic approach maintains reliable capacity information while minimizing the total time lost to measurement operations.

Inventive Principle:

Principle #19Periodic action

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 faster and more accurate determination of battery capacity, reducing battery degradation and improving SOC estimation accuracy, while conserving energy by transferring it back to the grid.

Implementation Method 1

a battery (ies) to provide power for vehicle operation

Methodology Applied

Scientific EffectElectrochemical reactions: Battery (electricity)

Implementation Method 2

During the charging time, the energy transferred to the battery can be measured (e.g., by integrating power transfer) to provide an accurate, current battery capacity of the battery

Methodology Applied

Scientific EffectEnergy measurement through power integration:

Data Source

PatentUS20250326316A1Measuring battery capacity of a battery installed on a vehicle through vehicle-to-grid (V2G) discharge and charge cycling operation

Publication Date: 2025.10.23 VOLVO TRUCK CORP

AI summary

Aspects disclosed herein involve measuring battery capacity of a battery installed on a vehicle through a vehicle-to-grid (V2G) discharge and charge cycling operation. The EV is configured to perform the discharge/charge cycle in the discharge/charge operational mode cooperatively through a power connection to a charging station configured to operate in a V2G mode to determine battery capacity. The charging station is not only controllable by the EV to charge its battery from grid power, but the charging station is also controllable by the EV to discharge energy from its battery back to the grid in a V2G operation. The EV can disable on-board, non-essential power consuming devices before starting the discharge cycle so that measured discharge energy can be controlled to be as steady state as possible to allow a more accurate measurement of the discharge energy from the battery.