When you introduce a completely new idea in battery technology, expect to get laughed a bit. That was some of the Internet's reaction to TankTwo when we learned about the unusual string cell battery concept earlier this year. Well, TankTwo didn't take the derision as a sign to quit, and is displaying its wares here at The Battery Show in Novi, MI this week. We got to talk with founder and CEO Bert Holtappels to see what's new with the battery that looks like an aquarium full of glowing rocks.
Tanktwo’s prototype refillable battery cell
Holtappels was busy showing the TankTwo to a gathered crowd, and from that presentation and our own discussion, here's what we learned about what's coming and the answers to some of your questions from the first go-round:
- TankTwo is indeed moving forward, and will have some sort of announcement with "one of the major players" about how its batteries are being used in some sort fo four-wheeled vehicle next year. Holtappels was not willing to share any more details than that, but at least we now know to keep an eye out when the calendar turns.
- As for what happens when the little egg-shaped nugget cells get "scrambled," the system not only has electronics that will reroute the power before the electricity can arc, its actually designed to prevent any movement of the eggs in the first place. First, the rounded cell shape means that once they're packed in the container, they have a hard time moving. Second, there are arms that push upward from the bottom to compress the space that the eggs are in, minimizing movement. Third, one of the container designs has a silicon "balloon" that expands from the top to shrink the space the pellets are in even further. Last, there is an ultracapacitor built in to cover the energy output should a big enough shake happen and disturb the nuggets for a second.
- The cells are made by a factory that used to make cells for Nokia, so it has excess capacity right now. Holtappels said that this gives TankTwo "pretty much unlimited capacity" to get cells now, enough to make 100 million cells with two or three months of lead time.
- Energy density is about the same as other batteries on the market – a little bit under 200 watt-hour per liter, volumetricly – but that can be adjusted based on the demands of the customer.
- Holtappels believes that, while most EVs will still be sold with one battery capacity and charged normally like we know today, there are some applications where buying the energy capacity separate from the battery itself makes sense. Think electric bus fleets, where some buses will go 50 miles today and others will go 100. If you have a fleet of 30 buses, you don't need to buy the battery capacity for all of them to go 100 miles, and you can save money if you buy a total of, say, 2,000 miles of capacity, and then can share it between the buses as needed. Personal EVs, too, can benefit, if you could have a cheap 60-mile EV most days , but go fill it with more nugget cells on Friday to go on a 300-mile road trip on the weekend.