Finnish EV start-up Donut Lab released independent testing results this week saying that its solid-state battery meant for EVs can charge to 80 percent in five minutes—or as fast as it takes to fill up a gas tank, depending on how big the gas tank is. The start-up is using its battery in a new electric motorcycle, but has even bigger plans for it.

Donut Lab’s solid-state batteries were tested in nearly perfect conditions, according to Electrek, which called the results of the test “impressive,” but also noted several caveats. Those caveats include concerns about battery density, whether the battery can hold up to tens of thousands of charging cycles, how the battery would fare in “extreme” temperatures, and also, of course, price, since a solid-state battery that can charge to 80 percent in five minutes isn’t much good if no one can afford it. The answer to all of those questions, for now, is: We’ll see.

The future of cars is electric, many people have been saying for many years now, though there have been several bumps along the road. The biggest problem at first was reliability and fixability, as consumers worried that batteries would die and brick their vehicles. Then, for a while, the problem was range anxiety, the fear that drivers might run out of juice in the middle of nowhere, necessitating a tow, though we’ve heard less and less about that as America’s EV charging network has vastly expanded from the early days.

A spate of worrying EV fires presented another challenge, as did affordability, since EVs have higher upfront costs than gas-powered cars, though, in the long-run, are cheaper for consumers. Government incentives in the U.S. have also run their course. Now, in China, EVs are simply better machines than the gas-powered cars that preceded them, though those products have not reached American shores, while consumer demand has soured here and in Europe because of the affordability concerns, and that, in turn, led to automakers like Ford, GM, Stellantis, and Porsche pulling back on once-ambitious plans.

Solid-state batteries like Donut Lab’s represent the next evolutionary step, and potentially a big one, with automakers including Toyota and Mercedes also working on the next-generation battery tech. A charging time of a few minutes, like in the latest results, has long been seen as the holy grail, so similar as it is to refilling a gas tank. But it will also be years before the tech can go mass market, and possibly even longer before chargers are widely available to do the fast charging. There’s also a question of whether such ultra-fast charging is even desirable, since it will likely be expensive. The long road to EV adoption continues to be a rough ride.