Fast, direct-current charging can charge an EV’s battery from about 20 percent to 80 percent in 20 minutes. That’s not bad, but it’s still about six times as long as it takes to fill the tank of an ordinary petrol-powered vehicle.

One of the major bottlenecks to even faster charging is cooling, specifically uneven cooling inside big EV battery packs as the pack is charged. Hydrohertz, a British startup launched by former motorsport and power-electronics engineers, says it has a solution: fire liquid coolant exactly where it’s needed during charging. Its solution, announced in November, is a rotary coolant router that fires coolant exactly where temperatures spike, and within milliseconds—far faster than any single-loop system can react. In laboratory tests, this cooling tech allowed an EV battery to safely charge in less than half the time than was possible with conventional cooling architecture.

A Smarter Way to Move Coolant

Hydrohertz calls its solution Dectravalve. It looks like a simple manifold, but it contains two concentric cylinders and a stepper motor to direct coolant to as many as four zones within the battery pack. It’s installed in between the pack’s cold plates, which are designed to efficiently remove heat from the battery cells through physical contact, and the main coolant supply loop, replacing a tangle of valves, brackets, sensors, and hoses.

To keep costs low, Hydrohertz designed Dectravalve to be produced with off-the-shelf materials, and seals, as well as dimensional tolerances that can be met with the fabrication tools used by many major parts suppliers. Keeping things simple and comparatively cheap could improve Dectravalve’s chances of catching on with automakers and suppliers notorious for frugality. “Thermal management is trending toward simplicity and ultralow cost,” says Chao-Yang Wang, a mechanical and chemical engineering professor at Pennsylvania State University whose research areas include dealing with issues related to internal fluids in batteries and fuel cells. Automakers would prefer passive cooling, he notes—but not if it slows fast charging. So, at least for now, Intelligent control is essential.

“If Dectravalve works as advertised, I’d expect to see a roughly 20 percent improvement in battery longevity, which is a lot.”–Anna Stefanopoulou, University of Michigan

Hydrohertz built Dectravalve to work with ordinary water-glycol, otherwise known as antifreeze, keeping integration simple. Using generic antifreeze avoids a step in the validation process where a supplier or EV manufacturer would otherwise have to establish whether some special formulation is compatible with the rest of the cooling system and doesn’t cause unforeseen complications. And because one Dectravalve can replace the multiple valves and plumbing assemblies of a conventional cooling system, it lowers the parts count, reduces leak points, and cuts warranty risk, Hydrohertz founder and CTO Martyn Talbot claims. The tighter thermal control also lets automakers shrink oversize pumps, hoses, and heat exchangers, improving both cost and vehicle packaging.

The valve reads battery-pack temperatures several times per second and shifts coolant flow instantly. If a high-load event—like a fast charge—is coming, it prepositions itself so more coolant is apportioned to known hot spots before the temperature rises in them.

Multizone control can also speed warm-up to prevent the battery degradation that comes from charging at frigid temperatures. “You can send warming fluid to heat half the pack fast so it can safely start taking load,” says Anna Stefanopoulou, a professor of mechanical engineering at the University of Michigan who specializes in control systems, energy, and transportation technologies. That half can begin accepting load, while the system begins warming the rest of the pack more gradually, she explains. But Dectravalve’s main function remains cooling fast-heating troublesome cells so they don’t slow charging.

Quick response to temperature changes inside the battery doesn’t increase the cooling capacity, but it leverages existing hardware far more efficiently. “Control the coolant with more precision and you get more performance for free,” says Talbot.

Charge Times Can Be Cut By 60 Percent

In early 2025, the Dectravalve underwent bench testing conducted by the Warwick Manufacturing Group (WMG), a multidisciplinary research center at the University of Warwick, in Coventry, England, that works with transport companies to improve the manufacturability of battery systems and other technologies. WMG compared Dectravalve’s cooling performance with that of a conventional single-loop cooling system using the same 100-kilowatt-hour battery pack. During fast-charge trials from 10 percent to 80 percent, Dectravalve held peak cell temperature below 44.5 °C and kept cell-to-cell temperature variation to just below 3 °C without intervention from the battery management system. Similar thermal performance for the single-loop system was made possible only by dialing back the amount of power the battery would accept—the very tapering that keeps fast charging from being on par with gasoline fill-ups.

Keeping the cell temperatures below 50 °C was key, because above that temperature lithium plating begins. The battery suffers irreversible damage when lithium starts coating the surface of the anode—the part of the battery where electrical charge is stored during charging—instead of filling its internal network of pores the way water does when it’s absorbed by a sponge. Plating greatly diminishes the battery’s charge-storage capacity. Letting the battery get too hot can also cause the electrolyte to break down. The result is inhibited flow of ions between the electrodes. And reduced flow within the battery means reduced flow in the external circuit, which powers the vehicle’s motors.

Because the Dectravalve kept temperatures low and uniform—and the battery management system didn’t need to play energy traffic cop and slow charging to a crawl to avoid overheating—charging time was cut by roughly 60 percent. With Dectravalve, the battery reached 80 percent state of charge in between 10 and 13 minutes, versus 30 minutes with the single-cooling-loop setup, according to Hydrohertz.

When Batteries Keep Cool, They Live Longer

Using Warwick’s temperature data, Hydrohertz applied standard degradation models and found that cooler, more uniform packs last longer. Stefanopoulou estimates that if Dectravalve works as claimed, it could boost battery life by roughly 20 percent. “That’s a lot,” she says.

Still, it could be years before the system shows up on new EVs, if ever. Automakers will need years of cycle testing, crash trials, and cost studies before signing off on a new coolant architecture. Hydrohertz says several EV makers and battery suppliers have begun validation programs, and CTO Talbot expects licensing deals to ramp up as results come in. But even in a best-case scenario, Dectravalve won’t be keeping production-model EV batteries cool for at least three model years.

In Menifee, Calif., six newly built homes are testing a first for North America: electric vehicles that can power houses through the Combined Charging System (CCS) high-power DC charging standard. Each home uses a host Kia EV9 electric vehicle connected to a Wallbox Quasar 2 bidirectional charger, allowing the car’s 100-kilowatt-hour (kWh) battery to run essential circuits during blackouts or periods when electricity prices are high. The setup is the first residential vehicle-to-home (V2H) system in the United States that uses the CCS standard. The CCS is the charging system commonly used in European and North American residential and public charging facilities.

Since July, the homes’ smart electrical panels have automatically managed two-way power flow—charging vehicles from the grid or rooftop solar, then reversing the flow of energy when needed. The system isolates each home from the grid during an outage, preventing any current from flowing into external power lines and endangering utility crews and nearby equipment.

“This project is demonstrating that bidirectional charging with CCS can work in occupied homes,” says Scott Samuelsen, founding director of the Advanced Power and Energy Program (APEP) at the University of California, Irvine, which is monitoring the two-year trial. “It’s a step toward vehicles that not only move people but also strengthen the energy system.”

Menifee means a lot

For more than a decade, two-way charging has been available—but mostly restricted to Japan. Back in 2012 the Nissan’s LEAF-to-Home program proved the idea viable after the Tōhoku earthquake and tsunami, but that Nissan system relied on the CHAdeMO standard, little used outside of Japan. Most North American and European manufacturers chose CCS instead—a standard that, until recently, supported only one-way fast DC charging.

That distinction makes Menifee’s V2H-enabled neighborhood notable: It’s the first CCS-based V2H deployment in occupied homes, giving researchers real-world field data on a technology that’s been long trapped in pilot programs. The pairing of the Kia EV9 SUV with Wallbox’s commercially available Quasar 2 can deliver up to 12 kilowatts of power from the vehicle to the home.

It’s a step toward vehicles that not only move people, but also strengthen the energy system.”
–Scott Samuelsen, UC Irvine

Elsewhere, momentum toward commercial V2H has slowed. Ford’s F-150 Lightning supports home backup through Sunrun, but Sunrun equipment is not CCS-compatible. What’s more, Ford has announced a production pause for the pickup truck, which has delayed expansion. GM’s Ultium Home—a V2H system that works with the automaker’s Cadillac Lyriq, Cadillac Escalade IQ, Chevrolet Blazer, Chevrolet Equinox, Chevrolet Silverado, and GMC Sierra EVs— faces similar setbacks. Tesla’s PowerShare V2H feature is still stuck in a limited, early commercial rollout, with bidirectional compatibility restricted to the company’s Cybertruck. Menifee, by contrast, is producing operational data in real households.

Why CCS Matters

When electric vehicles first hit the market, CCS was designed for one job: to move power quickly from the grid to the car. The main goal was reliable, standardized, fast charging. That fact helps explain the difference between CCS public chargers (many of which are rated for 350 kW or more) and their CHAdeMO-based counterparts, which typically max out at 100 kW (but are capable of providing home backup or grid services).

Bidirectional operation wasn’t included in the original CCS standard for several reasons. Early automakers and utilities worried about safety risks, grid interference, and added hardware cost. So CCS’s original communication protocol linking EVs and charging stations—ISO 15118—didn’t even include an electronic handshake for power export. The 2022 update, ISO 15118-20, added secure two-way communication, enabling CCS vehicles to supply energy to buildings and the grid.

Wallbox’s Quasar 2 residential charger implements the update through an active-bridge converter circuit built with silicon-carbide transistors, achieving efficient bidirectional flow. Its 12-kW power rating can support typical critical loads in a house, such as heating and cooling, refrigeration, and networking, says Aleix Maixé Sas, a system electronics architect at Wallbox.

As the company’s name humbly suggests, Wallbox’s chargers look like plain old boxes—although they contain high-tech components.Wallbox

The Menifee blueprint

Each of the Menifee homes outfitted with a V2H system combines a rooftop solar array with a 13-kWh SunVault stationary battery from SunPower. During normal operation, solar energy powers daily household loads and charges the stationary battery. On abundantly sunny days, the solar panels can also top up the Kia EV9’s battery. When the grid fails—or when energy prices spike—the home isolates itself: Solar power and energy stored in the SunVault keep essential systems and appliances going, while the EV battery extends power if the outage persists.

This past summer, the UC Irvine researchers tracked how solar output, stationary storage, and vehicle power interacted under summer demand and wildfire-related grid stress. They found that “the vehicle adds a major resilience feature,” according to Samuelsen, who is the Menifee project manager. “It can relieve grid strain, increase renewable utilization, and lower costs by supplying power during peak-rate hours.”

Engineering the Two-Way Home

Home builders and the makers of electric vehicle service equipment such as Wallbox are not the only entities reconsidering how to meet the engineering demands V2H introduces. Utilities, too, must make changes to accommodate bidirectional power flow. Interconnection procedures and energy pricing structures are among the factors that must be redesigned or reconsidered.

A Glimpse of the Energy Future

Analysts expect double-digit annual growth in bidirectional-charging system sales through the late 2020s as costs fall and standards mature. In regions facing wildfire- or storm-related outages and steep time-of-use pricing curves, projects like Menifee’s are showing a clear path toward the use of cars as huge and flexible energy reserves.

When EV batteries can supply energy for homes as easily as they do for propulsion, the boundary between transportation and energy will begin to disappear—and with it, old concepts regarding who’s an energy supplier and who’s a customer.