While Tesla is busy shouting about how awesome its new Model S is with 375 miles of range, and then under-delivering in real world testing, Our Next Energy, a startup in Southeast Michigan is retrofitting its own batteries into and older Model S and doing a road trip more than double that without charging. While this is still a proof-of-concept prototype battery, the goal is to turn this into a big business re-powering old Teslas to do big miles.

While ONE, Inc. doesn’t provide any exact details about the battery, we can assume that this battery holds a whole lot more batteries than the original Tesla pack had. The largest Tesla pack right now is around 100 kWh of energy storage. If we assume a standard Model S achieves efficiency around 3.5 mi/kW in ideal conditions, that 752 mile road trip would take at least 214 kWh. So how do you fit twice as much battery in the same volume? It would seem that Our Next Energy has figured out some energy density tricks that Tesla doesn’t yet have nailed down, while also packaging things tighter and with hand-built tolerances that Tesla’s mass production factories can’t manage.

At a steady-state 55 mph on a dynamometer with no wind resistance the car managed to run 882 miles on that same battery! Obviously that would be nearly impossible, unless you were running with a 60 mph tailwind the whole way. And one must presume that this test was conducted indoors at a reasonable temperature. Pushing that same battery into service to drive through a Michigan winter and still returning 750 miles non-stop is pretty impressive.

The route took ONE engineers from its headquarters in Novi up across the legendary Mackinac Bridge, back down through the state capital in Lansing, back across to Detroit, then back to Novi. All of that was done without a single stop to charge. That’s pretty cool, and extremely impressive. Apparently no modifications were made to the car other than the battery. Presumably there is a slight aerodynamic advantage to the ONE battery pack’s truly flat floor, but other than that, it looks like a pretty stock Model S. With these temperatures and road conditions, it would be unlikely that a standard Tesla would even make it 350 miles without a charge, let alone 750!

“We want to accelerate the adoption of electric vehicles by eliminating range anxiety, which holds back most consumers today,” said Mujeeb Ijaz, Founder and CEO of ONE. “We are now focused on evolving this proof-of-concept battery into a new product called Gemini, which will enable long distance trips on a single charge while improving cost and safety using sustainable materials.”

Gemini is the name of the company’s battery retrofit for Tesla Model S. It doesn’t provide much information about Gemini beyond the stated range test and this one rendered image of the pack on the company’s website. There’s also no mention of what one of these bad boys might cost, but I can assure you it won’t be cheap. You can buy used 100 kWh Tesla packs on ebay right now for around $25,000, if that gives you any idea what big batteries cost these days.

That said, how much is it worth to you to be able to drive 750 miles non-stop? 30 grand? 50 grand? 75 grand? Plus the cost of buying a used Tesla Model S? For some people that might be true, but certainly not for me. It’s a really cool idea, but I’m not sure how much practical application there is for such a battery retrofit. 750 miles is about two months of daily use for the average American. Why would you need the ability to drive for two months without charging?

ONE, which was founded in 2020, claims its batteries are engineered with a focus toward safer battery chemistries with more sustainable materials. The company plans to launch its first product —, presumably for grid energy storage and off-grid power backup — later this year. Gemini for Tesla Model S applications is anticipated to hit the market in 2023.