Chinese family-owned company Shenzhen Toomen New Energy is tough to find, at least on the English-language internet, but Belgian electronic engineer Eric Verhulst bumped into Toomen representatives on a tiny stand at the Hannover Messe expo in Germany back in 2018, while looking for next-gen battery solutions for an electric mobility startup he was running.

The Toomen team made a hell of a claim, saying they'd managed to manufacture powerful supercapacitors with the energy density of lithium batteries. "Of course, that's an unbelievable claim," Verhulst told us. "It's a factor of 20 better than what, for example, Maxwell had at the time. So I took my time, went over there, looked at their tests, did some tests myself, and I got convinced this is real. So at the end of 2018, we made an agreement to become their exclusive partner."

According to Verhulst, when he and his team got these "power capacitors" into the lab, they performed even better than they looked on the spec sheet. He tried to break them with charge and discharge rates up to 50C, more than double their rated capacity. They refused to fail. He left them fully charged for months at a time, and found them still well charged when he picked them up again. The University of Munich tested and confirmed their ability to handle temperatures down to -50 ºC (-58 ºF) and up to 45 ºC (113 ºF) without any heating or cooling systems.