OptiGrid's Approach to EV Interoperability
- Umit Demir
- Jul 23
- 3 min read
Updated: Jul 24
Why "It Charged Once" Isn't Good Enough:
When most people think about EV charging reliability, they think about uptime and whether the charger is on or off. But there's a deeper layer of complexity that doesn't get talked about nearly enough: whether a charger can actually complete a successful session with the specific vehicle in front of it. That's the interoperability problem, and it's one we take very seriously at OptiGrid.
The CCS Protocol Isn't as Uniform as It Sounds
Most DC fast chargers in the U.S. market use the Combined Charging System (CCS) protocol to communicate with the vehicle being charged. The problem is that "CCS compliant" doesn't mean every manufacturer has implemented it the same way. Different automakers, and in some cases different models from the same automaker, have made their own implementation decisions. Those differences create friction points that can cause a charging session to fail.
What makes this particularly tricky is that success with one model doesn't carry over to the next. If we've validated that our charger works with a GM Hummer EV, that does not guarantee it will work with a Chevy Bolt, even though both are GM vehicles that use broadly similar platforms. Each model has to be validated on its own merits.
What EV Interrupt Testing Actually Covers
Our validation process includes multiple testing layers: unit tests, regression tests, and subsystem- and system-level tests across both hardware and software. When it comes to interoperability specifically, everything comes down to what we call EV interrupt testing, which covers the full arc of a charging session.
The first phase is pre-charging. Before any energy flows, the charger and vehicle go through a handshake. The charger needs to ramp up to the right voltage and current levels and confirm that both sides are ready to proceed. If that initialization doesn't complete cleanly, the session fails before it starts.
The second phase is active charging. Once energy starts flowing, the vehicle's battery management system continuously tells the charger what it can accept, how much current, and at what voltage, at any given moment. The charger has to follow those instructions in real time. This is a continuous dialogue that must be held throughout the session.
The third phase is session termination. Ending a session correctly matters just as much as starting one. A graceful termination protects the vehicle's battery and ensures there are no safety issues on either end. We don't consider interrupt testing complete until all three phases have been validated successfully.
Every issue we find gets logged in our ticketing system and stays open until it's resolved. That discipline is what keeps field quality predictable.
The Target List Keeps Moving
Our working definition of interoperability is ensuring that our chargers can successfully charge all passenger-segment EVs sold in the United States and Canada. We maintain a running list of validated models and continuously work through it.
The challenge is that the list is never finished. New models enter the market. Existing models get updated, sometimes with new battery platforms that change charging behavior even though the nameplate stays the same. A Chevy Bolt that we validated several years ago may not behave the same way as the current model year. We have to keep pace with the market, not just check a box and move on.
What the Lab Tells You About the Field
The issues you find in the lab are the issues you will see in the field. And the issues you miss in the lab will surface in the field, at scale, across hundreds or thousands of deployed units.
That's why coverage and rigor aren't optional. Being able to charge a vehicle in a controlled environment is not the same as being confident it will charge reliably in the field. The gap between those two things is exactly what interrupt testing is designed to close.
Going forward, our focus is on testing both better and faster. Better means expanding vehicle coverage and improving our diagnostic tooling to capture more data during a session. Faster means automating manual steps in our testing process so we can run more iterations and reproduce issues more quickly. Both are already in execution.
