From protocol support to real-world vehicle compatibility, system reliability and commercial deployment
When a charger manufacturer says its product "supports ISO 15118" or is "V2G-ready", what does that actually mean?
Does it have the necessary communication hardware and a basic protocol implementation, or has it already been tested with real vehicles from different manufacturers? Can it handle communication interference, interrupted charging sessions, changing power limits and differences in vehicle behaviour? When a new vehicle or software update introduces an unexpected issue, how quickly can the manufacturer identify and resolve it?
For customers, the questions extend beyond the specification sheet: what has been tested, which vehicles the charger works with, how it behaves under demanding conditions, and how well it can adapt to future changes.
These differences are not always apparent when choosing a charger. As new vehicles enter the market, vehicle software receives OTA updates, and chargers become more closely integrated with EMS, CPMS and other energy systems, compatibility and ongoing engineering support have a direct bearing on long-term integration and operating costs.
It is therefore worth looking beyond whether a feature is listed to how thoroughly it has been implemented and tested, and whether the manufacturer has the expertise to maintain and improve it.
Over the past several months, NexBlue has continued standards testing, laboratory validation of bidirectional power flow, real-vehicle interoperability testing and backend integration. We have also put vehicle identification into practical use through AutoCharge. Underpinned by our in-house hardware and software development, this work is taking our ISO 15118 implementation towards practical V2X deployment.
1. Progress so far: from standards testing to real vehicles
TÜV Rheinland: full ISO 15118 protocol testing
NexBlue has completed systematic protocol testing at TÜV Rheinland, covering the full set of ISO 15118-2 and ISO 15118-20 test cases.
The tests covered connection establishment, protocol message exchange, secure communication, charging parameter negotiation and the relevant bidirectional communication sequences. They assessed our implementation against the requirements of both standards.
Building on this work, we have extended testing to actual bidirectional power flow, real vehicles, backend systems and interoperability across multiple OEMs.
ElaadNL: actual bidirectional power flow
Between 2 and 4 February 2026, NexBlue carried out ISO 15118 testing at ElaadNL. This covered AC HLC, Plug & Charge and bidirectional charging, including SLAC, TLS 1.2 / 1.3, EXI, charging parameter negotiation and EIM.
Using a Keysight vehicle emulator, NexBlue achieved approximately 19 kW of reverse power flow. The power level was limited by the emulator's capacity.
This was not just an exchange of protocol messages: electrical energy physically flowed in the reverse direction, demonstrating bidirectional energy transfer in the test setup.
Monta: end-to-end Plug & Charge with real vehicles
On 6 and 9 February 2026, NexBlue completed real-vehicle ISO 15118-2 Plug & Charge testing with Monta. Testing included vehicles such as the Volkswagen ID.3, OCPP 1.6 backend integration, and the download and validation of Hubject contract certificates through Monta.
The end-to-end connection was:
Real vehicle ↔ NexBlue charger ↔ Monta backend and certificate services
The tests brought the vehicle, certificate handling, charging session and backend services together in a single validation process.
AutoCharge: automatic authorisation for everyday charging
Alongside end-to-end Plug & Charge validation, NexBlue has applied its vehicle communication and identification capabilities to AutoCharge. Development of the associated OCPP functionality is complete.
Once enabled, AutoCharge recognises compatible vehicles when they are plugged in and authorises charging automatically. Drivers do not need to tap a card or open an app for each charging session.
AutoCharge uses vehicle identification, while the Plug & Charge implementation described above uses contract certificates. These provide different approaches to automatic authorisation for fleets, charging operators and everyday charging.
Seven vehicle manufacturers: cross-vehicle interoperability
To date, NexBlue has carried out ISO 15118 and V2X interoperability testing with engineering teams and vehicles from 7 automotive OEMs.
For the functions made available on the participating vehicles, NexBlue successfully completed the relevant interoperability test sequences with almost all participating OEMs.
The same NexBlue implementation has been tested against different OEMs, EVCC implementations, software versions and vehicle behaviours.
Our progress now spans five milestones: protocol testing at TÜV Rheinland, bidirectional power flow at ElaadNL, end-to-end Plug & Charge with Monta, automatic vehicle authorisation through AutoCharge, and cross-vehicle interoperability testing with OEMs.
2. What sets an ISO 15118 implementation apart?
Compatibility across real vehicles
ISO 15118 provides a common standard, but manufacturers do not all implement it in the same way.
Differences can arise in EVCC hardware and software, PLC communication, message timing, state machines, parameter handling, enabled functions, and certificate and security mechanisms. The interaction between the vehicle's OBC, BMS and EVCC also affects its behaviour. An OTA update can introduce further changes, even within the same vehicle model.
A successful emulator test does not establish compatibility with a real vehicle. Equally, working with one vehicle does not establish compatibility across other vehicle platforms.
NexBlue is expanding testing across manufacturers, EVCC implementations, vehicle models and software versions. Findings from those tests—including timing differences, edge cases and compatibility issues—feed back into our product development.
Compatibility has to be maintained as vehicles and their software evolve.
Testing beyond normal operating conditions
Completing a charging session under ideal conditions confirms that the basic sequence works.
Real installations also have to contend with PLC interference, reduced signal quality, communication timeouts, unexpected messages, mismatched vehicle and charger states, interruptions, stop-and-resume commands, changing EMS power limits, transitions between charging and discharging, and certificate or authentication errors.
One OEM paid particular attention to these conditions during our joint testing. Alongside normal communication and charging, its engineers tested PLC signal quality, dynamic current adjustments, stopping and resuming charging, and the interaction between the vehicle and charger in different operating states.
An implementation needs to do more than support the expected sequence. It also needs to handle interruptions, recover correctly and remain reliable when conditions are less predictable.
Resolving new issues during testing
New vehicle models, software releases and operating conditions will continue to create compatibility challenges.
The practical question is whether the manufacturer can diagnose an issue across the system, modify the relevant part of the implementation and test the result promptly.
During OEM test sessions, NexBlue has repeatedly identified issues, adjusted code or configuration and retested on site. This allows the teams to resolve issues and continue testing during the session, rather than simply logging them and waiting for a later software release.
3. The engineering behind it: in-house hardware and software
NexBlue treats ISO 15118 as an integral part of the charger architecture rather than as a standalone software feature.
On the hardware side, we design the communication hardware and signal path around a PLC chipset and integrate them directly into our charger platform.
On the software side, we develop our own ISO 15118 protocol stack and integrate it with the EVSE state machine, charger control logic, power control, security and certificate handling, and OCPP/backend communication.
This gives our engineers direct control from the communication hardware through to charger control and backend reporting.
Many charger manufacturers use third-party communication modules or ready-made protocol stacks. These can provide a quicker way to introduce ISO 15118 functionality and reduce the initial development effort.
NexBlue has chosen to develop and retain control of the core hardware and software in-house. Our R&D team brings together expertise in hardware, embedded software, communication protocols, charging control and backend systems.
Integrating an ISO 15118 feature is not the same as being able to investigate and improve it—from the physical signal and protocol exchange through to the charger's response.
Problems often cross the hardware–software boundary
If a vehicle intermittently fails to establish PLC communication, the cause might involve signal strength, electrical noise, hardware compatibility or the vehicle's receiver performance. It might also lie in SLAC, protocol timing or the state machine.
Another example is a charger receiving a lower power limit from an EMS while an ISO 15118 session is already active. The system needs to coordinate vehicle parameter negotiation, protocol state, the charger's internal state, actual power delivery, the EMS command and the status reported to the backend.
Investigating these issues can involve the vehicle's EVCC, PLC hardware and signals, ISO 15118 messages, the EVSE state machine, charger control logic, power control, the EMS and the OCPP connection.
Access to both the hardware design and the software implementation allows our engineers to investigate across these boundaries.
A shorter path from diagnosis to retesting
When communication hardware and protocol functions sit inside a third-party module that the charger manufacturer cannot inspect or modify, resolving an issue may involve exporting logs, submitting them to the supplier, waiting for analysis and a firmware or SDK update, integrating the change, and arranging another vehicle test.
Hardware or low-level communication issues may require further supplier involvement.
With control of our own implementation, NexBlue's engineers can investigate the hardware and software together, make the necessary changes and retest directly. This is the approach used during our on-site OEM testing.
One OEMs assessment also extended beyond protocol behavior to NexBlue's PLC hardware, signal quality and communication stability.
The aim of in-house development is practical: better compatibility, reliable system behaviour and less delay between finding an issue and resolving it.
4. Feedback from OEM testing
The OEM engineers used test equipment to assess NexBlue's PLC signal quality and hardware communication path.
Their testing covered normal communication and charging, communication stability, dynamic EMS power adjustments, stopping and resuming charging, and fault and edge-case scenarios.
In the EMS tests, they examined how the vehicle and charger responded when current limits increased or decreased, charging was stopped, and the session was subsequently resumed. The focus was on keeping the vehicle and charger in step throughout those changes and ensuring correct recovery.
OEM feedback was highly positive, with several teams requesting additional joint testing sessions and test units for further evaluation in their own laboratories. NexBlue is continuing these collaborations through remote and on-site testing across additional vehicle models, EVCC implementations, software versions, fault scenarios, and post-update regression testing.
5. Observations from seven vehicle manufacturers
Testing across seven vehicle manufacturers revealed significant variation in ISO 15118 implementation, AC V2G maturity, EVCC/OBC behavior, and the bidirectional functions available for validation. While several OEMs are actively developing AC V2G and enabled meaningful interoperability testing, others remain at earlier stages, with limited V2X functionality or unresolved communication issues requiring further joint work.
6. Why NexBlue is prioritising AC V2G
We believe AC V2G is the better fit for residential use and large-scale distributed deployment. It is the V2X approach we are prioritising.
Power conversion takes place in the vehicle
The main architectural difference between AC and DC V2G is where bidirectional DC/AC conversion takes place.
In DC V2G, an external bidirectional charger converts DC power from the vehicle battery into AC power for the home or grid.
In AC V2G, the vehicle's bidirectional OBC performs that conversion, and the vehicle supplies AC power through its AC connection. The home installation therefore does not need a separate bidirectional DC power-conversion unit.
This affects equipment cost and size, installation requirements, maintenance and the practicality of deploying the system across large numbers of homes.
Residential V2G has to be affordable and straightforward to install
A solution intended for widespread residential use has different demands from a small number of specialist projects.
Requiring a separate, complex and expensive bidirectional DC power unit in every home adds cost, takes up space and makes installation more demanding.
AC V2G keeps the main power-conversion function in the vehicle while retaining an AC charging architecture at the property. We are focusing on this approach because it offers a route to simpler home-side equipment, lower system costs and easier installation at scale.
What we are seeing in OEM development
In our testing and engineering discussions, three OEMs have all been actively progressing AC V2G, while One OEM`s engineers have also been revisiting the approach.
OEM 5 has made a relatively comprehensive set of AC V2G functions available for joint testing. Two OEMs have both expressed interest in continuing the work with NexBlue test units.
Our development priorities include real-vehicle AC V2G compatibility, fault and edge-case testing, PLC communication, ISO 15118, OCPP 2.1, EMS/HEMS integration and practical energy applications. The objective is a system ready for deployment, rather than an isolated feature on a specification sheet.
7. Commercial V2G also requires grid integration
ISO 15118 provides communication, authentication, parameter negotiation and charging-control messages between the vehicle and charger.
Commercial AC V2G deployment also requires work on grid compliance, bidirectional power control, grid response, protection and anti-islanding, metering, EMS/HEMS control, OCPP/backend integration, and the relevant testing and certification.
Germany's VDE-AR-N 4105:2026-03 includes requirements and verification procedures for charging equipment capable of exporting power to the grid. NexBlue is progressing the corresponding grid-integration and validation preparations for its target markets.
Vehicle communication, charger control, energy management, backend integration, grid control and local certification all need to come together for deployment.
8. V2H as an early application
V2X can deliver value before grid-trading arrangements and VPP business models are fully established.
For homeowners, V2H applications include backup power, increased solar self-consumption, peak shaving, time-of-use optimisation and home energy management.
Home backup is a direct use case. In a backup configuration, the system isolates the home from the public grid and switches the supply so that the vehicle can power household loads during an outage.
During normal grid-connected operation, the vehicle can also work with a HEMS to optimise energy use within the home. Grid export opens up further applications, including flexibility services, aggregation and VPP participation.
In some markets, we expect V2H and home energy management to come first, followed by broader V2G services as the necessary grid and market arrangements become available.
9. Priorities for the next six months
From Q4 2026 to Q1 2027, NexBlue will focus on six areas.
1. Broaden vehicle coverage
Continue testing with the OEMs, while expanding coverage across vehicle models, EVCC implementations and software versions. This includes checking compatibility after vehicle OTA updates.
2. Extend fault and edge-case testing
Expand testing of communication timeouts, state mismatches, unexpected interruptions, stopping and resuming charging, certificate errors, changing power limits and bidirectional power transitions.
The focus is on reliable behaviour under demanding conditions, not just successful completion of a normal test sequence.
3. Improve PLC communication
Continue improving signal quality, communication margin, resilience to interference and stability across different vehicles and connection conditions.
4. Extend AC V2G testing with real vehicles
As OEMs make more bidirectional functions available, continue validating parameter negotiation, bidirectional power control, transitions between charging and discharging, state changes, dynamic EMS control, and stop-and-resume behaviour.
5. Advance OCPP 2.1 and energy-system integration
Continue OCPP 2.1 development and integration across the following system:
Vehicle <-> NexBlue charger <-> CPMS <-> EMS / HEMS <-> Aggregator / energy system
This work connects vehicle capabilities with energy-management and dispatch requirements.
6. Prepare for grid connection and certification
Work through the grid-code, protection, testing, certification and project connection requirements for each target market.
10. NexBlue's V2X roadmap
Phase 1: core technology
Develop and retain in-house control of PLC communication hardware, the ISO 15118 protocol stack, EVSE state machines, charger control logic, power control, security and certificate handling, and backend integration.
Phase 2: validation and practical implementation
Complete ISO 15118 protocol testing at TÜV Rheinland, demonstrate actual bidirectional power flow at ElaadNL, and validate real-vehicle Plug & Charge and backend integration with Monta. Apply vehicle identification and automatic authorisation to everyday charging through AutoCharge.
This phase combines validation of the underlying technology with the implementation of a practical charging feature.
Phase 3: multi-OEM interoperability and deployment preparation
Focus period: second half of 2026 to Q1 2027.
Expand testing across vehicle manufacturers, models and software versions, including continued work in OEM laboratories, fault and edge-case behaviour, PLC performance, AC V2G, integration with EMS/HEMS and OCPP 2.1, and preparation for grid connection and certification.
The goal is cross-OEM compatibility, reliable real-world operation, integrated energy management and grid readiness.
Phase 4: commercial V2H and V2G deployment
Target deployment window: 2027 to mid-2028.
Deployment will follow the conditions in each market, progressing from V2H and home energy management to V2G, flexibility services, aggregation and VPP participation.
Ongoing work will include maintaining interoperability as new vehicles and vehicle software versions are introduced.
More than a "V2G-ready" label
NexBlue has built its core in-house hardware and software capability across PLC communication, ISO 15118, charging control and backend communication. We continue to validate that work through standards testing, bidirectional power tests, real-vehicle testing and joint engineering sessions with OEMs. AutoCharge puts vehicle identification and automatic authorisation to work in everyday charging.
Our R&D team covers the hardware, embedded software, communication protocols, charger control and backend systems needed to investigate and improve the implementation.
The next steps are to broaden vehicle coverage, test more demanding operating conditions and deepen energy-system integration as we move towards commercial AC V2G and V2H deployment.