In Part I of this interview, Mike Calise, CEO of Tellus Power, discussed how engineers ensure grid stability, system safety, and reliability in high-power dc charging networks.
Mike Calise, CEO of Tellus Power.
In this second installment, the conversation turns to the technologies that keep those systems operating efficiently over time. Calise explains how engineers are addressing challenges in thermal management, cable and connector design, and communication between chargers and vehicles.
He also explores vehicle-to-grid (V2G) integration, a technology that enables electric vehicles to send stored energy back to the grid to help balance demand and support renewable energy generation.
Here’s what he had to say…
What are the biggest thermal management challenges in dc fast-charger design, and how are they addressed?
High-power density generates significant heat in components such as rectifiers, busbars, capacitors, and magnetics. This heat can lead to hot spots, high ambient temperatures, clogged filters, and corrosive air in the charger, all of which can all reduce reliability and shorten component life. Uneven airflow or coolant distribution can cause power derating or nuisance trips.
To address this, most systems use a mix of forced-air cooling at the cabinet level and liquid cooling on higher loss components. Wide bandgap semiconductors like silicon carbide improve switching efficiency and reduce heat at the source.
Systems also include dense thermal sensors with predictive derating controls, serviceable filter and cooling assemblies, and protective coatings or meshes for harsh environments. Remote monitoring and analytics are used to identify rising thermal resistance or fouled filters before failures occur.
How do cable design and liquid-cooled connectors enable fast and ultra-fast charging without overheating?
Cables for ultra-fast charging use finely stranded conductors and insulation materials rated for continuously high temperatures to keep resistance and heating low. For higher currents, liquid cooling circulates coolant through the cable and around the connector pins to remove heat where it is generated.
These assemblies include temperature sensors so the charger can reduce current if needed before surface temperatures exceed safe touch limits. By removing heat with liquid cooling, the cable diameter can be smaller and more flexible, improving ergonomics for drivers while still enabling very high charging power.
What are the communication and interoperability challenges when integrating dc fast chargers with different EV brands and charging standards?
Although standards like CCS, NACS, ISO 15118, DIN 70121, OCPP, and OCPI are widely used, there are still differences in interpretation and implementation between OEMs. These variations can cause handshake failures, pre-charge mismatches, or contactor timing issues when a car plugs in. Differences in insulation monitoring thresholds, fault handling, or pre-charge targets can also create session aborts.
Another challenge is protocol drift, where vehicles and chargers run different software or firmware versions. Plug & Charge, PLC quirks, or security certificate handling can vary by OEM and network. Roaming and payment processing can introduce further points of failure that look like charger faults to the driver.
To manage this, engineers perform interoperability testing with major vehicles in the lab and field, building flexibility into protocol stacks to handle timing windows or fallbacks. Remote diagnostics, trace capture, and over-the-air updates are also important to quickly identify and correct issues. Widespread corporate participation in industry test events and conformance programs helps keep equipment aligned as standards evolve.
What role does standardization of connectors, protocols, and communication play in reducing complexity across charging infrastructure?
Driver satisfaction is essential to success in the industry. It is critical that all chargers and vehicles follow the same standards (CCS/NACS, ISO 15118, OCPP) to ensure that no matter what cars drivers use, where they travel, what service providers they choose, or what charger models they encounter, they have a seamless experience and can start charging successfully on the first try.
What role could vehicle-to-grid (V2G) play in stabilizing grids with high renewable penetration, and what limitations remain?
A high-power dc fast charger from Tellus Power, designed for scalable performance and compatibility across charging standards.
Renewable energy brings environmental and economic benefits, but it also has limitations because of its variable output. With V2G and coordinated fleets, excess energy can be stored in EV batteries and quickly discharged when renewable output is low. This balances grid load, shaves peaks, and provides support during outages, improving resilience where renewable penetration is high.
It is a promising technology with many advantages, but there are important considerations: cybersecurity, the need for more EVs and chargers that support V2G, technology to minimize battery degradation, and regulation and incentives to accelerate adoption.
What engineering hurdles must be solved before V2G can scale beyond pilot programs?
In an effort to bring forward the scaling of V2G, utilities have joined together to work towards establishment of standards of control and communication to incorporate this newest entry of additional grid energy source.
The inclusion of millions of V2G-enabled EVs would provide a variable, flexible system of Distributed Energy Resources (DERs), that provide ready access backup during times the grid capacity is challenged. Future controls would manage the dynamic two-way power flows as scores of EVs come online.
In pilot programs, the whole system runs in a controlled environment and settings with a limited number of participating units. When scaling up for mass deployment, more things should be considered, such as the simultaneous control and coordination among distributed hundreds or thousands of nodes, number of simultaneous distributed failure and troubleshooting the system can handle, etc.
To expedite the growth of V2G, established universal standards have been expanded to make interoperability much easier. Adoption of standards and protocols such as ISO 15118-20 (secure bidirectional communication), OCPP 2.1 (charger management) and IEEE 2030.5, UL1741 SB, enhance the seamless communication and control of the V2G resources.
The utilities, OEMs, and charger manufacturers are developing more sophisticated and robust battery management systems (BMS) that ensure long-life and expanded usability for vehicle batteries. These advanced battery management systems, along with state-of-charge algorithms on the vehicles, will accelerate grid V2G participation and the grid stability benefits that will result.
Lastly, companies need to continue to build on cybersecurity measures as they include more V2G options in their facilities.
Filed Under: Charging, FAQs, Featured, Featured Contributions, Q&As, Vehicle-to-Grid (V2G)