Bi-Directional On-Board Charger for Direct EV-to-EV DC Charging

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Solution Overview

Problem

Existing vehicle-to-vehicle charging systems suffer from low efficiency due to power losses when charging through the on-board chargers of both electric vehicles, resulting in limited range for electric vehicles, especially in remote locations without charging stations.

Innovation Solution

The method involves controlling a bi-directional on-board charger of a first electric vehicle to provide DC power directly to the energy storage system of a second electric vehicle, bypassing the on-board charger of the second vehicle, thereby reducing power losses and increasing charging efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If DC power is transferred through the on-board chargers of both electric vehicles, then vehicle-to-vehicle charging can be achieved, but power losses increase and charging efficiency decreases

Engineering Contradiction:

Improvevehicle-to-vehicle charging capabilityVSAvoidpower losses

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent extracts the load vehicle's on-board charger from the charging path by enabling direct DC-to-DC power transfer between the source vehicle's energy storage system and the load vehicle's energy storage system. This bypasses the inefficient AC conversion process that would otherwise occur through both vehicles' on-board chargers, eliminating unnecessary energy conversion steps and reducing power losses.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The source vehicle's bi-directional on-board charger is designed to perform multiple functions: it can both charge the source vehicle from the grid and discharge to charge the load vehicle directly. This multi-functionality allows the system to adapt to different charging scenarios (AC charging from grid, DC charging from another vehicle) without requiring separate dedicated equipment for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If conventional vehicle-to-vehicle charging through dual on-board chargers is used, then charging can be performed, but charging efficiency is reduced due to multiple conversion steps

Engineering Contradiction:

Improvecharging speedVSAvoidenergy loss

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent establishes a continuous DC power transfer path from the source vehicle's energy storage system directly to the load vehicle's energy storage system, eliminating the interruptive AC conversion steps. This continuous action maintains higher power levels throughout the transfer process, improving charging speed while reducing energy loss compared to the conventional method with multiple conversion stages.

Inventive Principle:

Principle #20Continuity of useful action

3Power

If bi-directional on-board charger converts DC to AC for vehicle-to-vehicle charging, then power can be transferred, but conversion losses occur reducing overall efficiency

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidconversion losses

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent replaces the mechanical/electrical conversion process (DC-to-AC conversion through the on-board charger) with a direct electrical connection for DC power transfer. By substituting the AC conversion mechanism with a direct DC connection, the system eliminates the conversion losses that would otherwise occur in the bi-directional on-board charger, achieving more efficient power transfer.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach enhances the overall charging system efficiency by reducing losses to half, achieving a higher efficiency compared to conventional methods, and enabling faster charging with reduced energy loss.

Implementation Method 1

controlling a bi-directional on-board charger of a first electric vehicle to provide a DC power from an energy storage system of the first electric vehicle

Methodology Applied

Scientific EffectElectrical energy conversion:

Data Source

PatentUS12269359B2Method and system for vehicle-to-vehicle charging of electric vehicles

Publication Date: 2025.04.08 VOLVO CAR CORP

AI summary

A method for vehicle-to-vehicle charging for electric vehicles, including: controlling a three phase bi-directional on-board charger of a first electric vehicle to provide a DC power from an energy storage system of the first electric vehicle at a first terminal L1 and a second terminal L2 of the three phase bi-directional on board-charger of the first electric vehicle; transferring the DC power from the first terminal L1 of the first electric vehicle to an energy storage system of a second electric vehicle, and from the second terminal L2 of the first electric vehicle to an energy storage system of a third electric vehicle.