Fully Charged in Six Minutes?

Nybolt and Callum demo a battery that can be charged so quickly that it wouldn’t need to be as big.

The Lotus Elise-based demonstration concept car for the Nyobolt/Callum fast-charging lithium-ion battery technology; the companies claim the smaller battery enabled by fast charging means much-reduced weight penalty compared to current EVs. (Nyobolt)

Battery technology company Nyobolt and UK-based design and engineering consultancy Callum are collaborating on a demonstration of new lithium-ion battery tech that would permit the full charge of a vehicle in about six minutes.

Various battery form factors displayed by Nyobolt. (Nyobolt)

The project uses a 2-seat sportscar based on the Lotus Elise. The Elise was designed in the early 1990s by Julian Thomson, who also designed the project vehicle. The concept was developed and executed by Callum. Thompson now is the design director at General Motors Advanced Design Europe, based in the U.K.

Nyobolt provided a charging demonstration using a 1 kWh battery in a closed cabinet, using a simple cooling plate to regulate battery temperature. A data logger showed that during the six-minute charge, the battery reached a maximum temp of 42° C (108° F).

Cylindrical Nyobolt fast-charge batteries in a laboratory rack. (Nyobolt

“We were charging initially at 12 (Celsius), so that would be a 12-minute charge”, explained Nyobolt Vice President of Operations and Engineering, Steve Hutchins, “We've actually got batteries that charge much faster than that, but for this purpose, that's where we think is a good sweet spot. And in terms of thermal management, one of the advantages of the cells is that they don't get very hot, so we can get away with a lot less heat management than you would think.

“We've tested those cells to over 2,000 cycles and it's still above 80 percent capacity at 12° C charging, a very high-speed charge rate, a very minimum degradation. Depending on your driving style, [longevitiy] could be five years, 10 years, or 20 years.” Hutchins suggested a typical charging-temperature range of around 35° to 40° C (95° to 104° F), in the range seen during the demonstration.

Nyobolt indicates that its silicon-carbide (SiC)-based power electronics are central to the 99%-plus conversion efficiency that aids in the ultra-fast charging time of its batteries. (Nyobolt)

The Callum/Nyobolt demonstrator is fitted with a 35-kWh battery. The potential for such rapid charging means that a large-capacity battery might not be necessary because recharging would take little more time than filling a conventional vehicle’s fuel tank. The battery could be used in hybrid, fuel-cell hybrid and ICE hybrid vehicles because it could recharge so rapidly. “We could make a hybrid battery do the job of a big battery, basically,” said Hutchins.Nyobolt’s core technology is the anode material. “It's the anode that limits the charging and everybody's been focused on the cathode”, says Hutchins; “That's more important on the discharge side. People have just had the same old anode for years and years, so we're focusing on the anode. But the anode doesn't work on its own. It's a system, there's probably a dozen components in one battery cell and they all have to work together.” Nyobolt’s U.S.-based team, under Chief Technology Officer Brian Barnett, includes engineers involved in developing Formula One’s KERS (Kinetic Energy Recovery System) battery, with extensive expertise in high-power batteries.

“The anodes are a lot more forgiving than the cathode material. We haven't really faced any issues at all”, Hutchins continues. “Obviously, there's a lot of engineering that's gone into the anode to make it last as long as it does, but we don't have any stability issues there, it's not limiting the life of the battery. When a battery dies, it's usually more to do with the cathode.”

Real-world testing on tap

Callum engineering director Adam Donfrancesco. (Nyobolt)

Road testing of the demonstrator is due to start in November 2023. Nyobolt’s first demonstration of the technology was not on a vehicle. “We started with a 12-volt battery in a robotic vacuum cleaner”, says Dr Hutchins, “We were able to show it charging in three minutes and then vacuuming for 30 minutes. Previously, it spent 15 percent of its time cleaning and 85 percent charging and we switched that around.” The idea then developed to see if the same concept could be achieved in an EV.

Balancing battery capacity with battery energy will be part of the trial process. Hutchins explains: “If we go for maximum charge rate, we won't match the energy of current batteries. If we match the energy of today's batteries — while that's possible — we wouldn't be able to get such a fast charge time. We could still get a faster charge than you could get with today's batteries, it just depends where you want to put that trade.

“So, we've got some customers who would like to charge in say, 15 minutes. We have other customers who would like to charge in seconds, so we design the battery to suit the application.” The battery can still be AC- or DC-charged, the same as current EV batteries.

The starting point for the demonstrator vehicle wasd 500 Nm (369 lb-ft) available.

“A lot of the time has been spent on thermal management, looking at cooling systems and the heating systems for the battery”, Callum Engineering Director Adam Donfrancesco told SAE International, “Obviously, we all know that the battery has a reasonable sweet spot in which to operate and the environmental sweet spot is much larger, so the crossover points mean you have to attack that with some active-cooling technology in order to do that.”

“When we move into the vehicle phase of the project, which we're just building up at the moment, we'll be looking quite significantly at tailoring that throttle calibration, because I think that's going to be quite interesting to drive. It's only 40 kg (88 lb) heavier than the original model on which it’s based, so we're very keen to keep that down so that the technology doesn't necessarily come with a weight penalty. You want a smaller battery because of the charging philosophy, so therefore you can achieve a sportscar level of performance and mass in that respect. We are optimizing with composites.”

Could the car become a production reality? “Callum has the capability for low-volume production. It would be interesting if demand is there”, said Donfrancesco.