Bye Looks To Lithium-Sulfur For Electric Aircraft Power


Bye Aerospace and OXIS Energy have announced a collaboration to develop and produce a Lithium-Sulfur (Li-S) “advanced battery cell for the high-voltage battery pack system to be considered for Bye’s future electric aircraft.” According to OXIS Energy CEO Huw Hampson-Jones, OXIS’ Li-S cells and battery systems are “over 50 percent lighter than the current Li-ion cell and battery systems” and are capable of achieving the energy density needed for Bye’s aircraft.

“A key measure of OXIS’ suitability is to be able to consistently produce cells in excess of 400 Wh/kg [watt-hours per kilogram], which are already undergoing evaluation,” said Huw Hampson-Jones. “OXIS expects to achieve 500 Wh/kg by early 2020.”

Bye Aerospace CEO George Bye says that the Li-S project is separate from current “agreements and intentions” related to the company’s eFlyer 2 electric trainer. Instead, it is aimed at the four-place eFlyer 4 and unnamed “future air taxi aircraft designs.”  Work on the project is scheduled to begin this September with the goal of moving toward production of commercial cells and battery systems over the following 18 months.

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Kate O’Connor works as a senior editor at AVweb. She is a private pilot, certificated aircraft dispatcher, and graduate of Embry-Riddle Aeronautical University.


  1. Until the power density of the batteries approaches that of conventional fuels, electric aircraft won’t achieve the same usefulness. I can see it used in motor gliders, and around the patch puddle jumpers, but many years away from approaching the same usefulness of a C-172. I may have missed it, but a 100 miles out and 100 back for that $100 burger still hasn’t happened in a practical aircraft. These proposed electric hovering air taxis still can’t get past 30-60 miles and would spend nearly all of their time recharging as 1 or 2 trips and the battery is depleted. Electric cars are just now getting to the practical point, and their weight issue isn’t a problem for them, and none of then could do a 600 mile day trip in a reasonable amount of time.

    • What do you mean by “approach”? With energy efficiencies of gas combustion engines hovering around 30% and electric motors at 80+% it doesn’t seem like the energy densities have to be that close.

      • This is a ridiculous comment!

        It IS true that internal combustion engines have a low energy efficiency but the FUEL is SO much more concentrated that it makes little difference. I have a chart produced by the US Energy Administration which ranks fuels / energy storage by volume and by weight. Gasoline is ranked at 1 (in much the same way as water is used as the comparison for specific gravity of liquids). NOTHING exceeds gasoline for storage of energy. Diesel is slightly more efficient but that has more to do with the design of the engine than the fuel itself. The chart has four quadrants … heavier or lighter than gas and energy content per unit volume compared to gas. In one simple chart, you can see the absolute folly of powering anything which requires a lot of energy from a battery. Batteries are darn near zero/zero on this energy comparison chart. You cannot change physics!

        At Airventure, the Airbus Vahana with eight 35kw electric motors has an endurance of 20 minutes … MINUTES !! Ridiculous. Unless and until batteries get more efficient by an order of magnitude, the whole idea is a pipe dream.

        Further … I live in a rural electric co-op area. We get a monthly magazine talking about things related to electric energy. They are worried that the grid cannot sustain everything going full electric, as well. Unless smaller nuclear power plants start being built, the current grid and generating system cannot sustain this idea.

        The motors ARE there. The energy storage isn’t … the improvement in battery energy densities is insufficient to make it a reasonable alternative and … that’s that.

      • Further, George Bye was gonna turn C172’s into electric motor powered airplanes. I went to his presentation in the AOPA tent at Airventure and asked him when I could expect MY energy pack to be delivered for my Skyhawk. I got a deer in the headlight look. Then I asked him what his electric airplane was gonna cost … answer … $375K. Right! I’ll be sure and buy one of his airplanes for that with an hour’s range.

        • Larry, although you make valid points, they are no different than those made against the internal combustion engine (ICE) over a hundred years ago. And still today, nothing beats steam when it comes to energy density (unless you go nuclear and beyond). Considering how the electric motor was already more efficient than a gasoline engine, those points don’t always seem to prevail.

          But more so than numbers, the human race, for all its flaws and grace managed to get two people on the moon with a mere calculator capacity of an onboard computer. Hovering electric aircraft is easier since the pace of development is exponentially faster than that of ICE.

          Reactions to eVTOLs today are also no different than those against helicopters 70 years ago. They are not efficient, yet they fly. The fundamental problem is using too much non-renewable resources with climatic consequences.

          In a reasonable world, your points might make sense but in this reality, we’ve seen far too many instances of inefficient but lucrative technology being pushed down our throats ad nauseam.

          • Nick, good points, but Larry would probably argue against the horseless carriage if given the historical opportunity.

  2. It’s all about the mission.
    If you’ve got a 20-minute, no-reserves mission, then by all means – buy a battery. Hell, buy two!

    But if you need to get somewhere – say, 600 nm in 4 hours or so – then you’d better buy a VERY long extension cord. Or just spend 10 minutes tanking up with kerosene or gasoline.

    Larry is absolutely right.

  3. Not sure how this is “better”, since the theory of AGW is, well, still a theory. Obviously even “if” the theory gets beyond the theoretical stage then GA training planes would still be irrelevant by any scientific calculation or even simple and reasoned critical thinking.

    What’s going to be the real test is that UNLIKE other 4-seaters, you cannot reduce fuel weight for increased payload.