Originally Posted by rickair7777

Somebody will come along and say "oh they'll improve that as technology advances"

Current Li battery technology achieves maybe 700 Wh/kg. But that's at the cell level, in a lab.

After you apply the overhead for the pack and onboard systems, you can practically achieve maybe 300 Wh/kg.

Of course improvements can and will be made. But the max theoretical specific energy of current Li cell technology, based on chemistry is about 1,000 Wh/kg. You can't do better than that without altering some of the fundamental laws of physics.

The most cutting edge tech I'm aware of is a Li Air battery. That can actually hack (not defeat) the 1,000 Wh/kg limit because it uses O2 in the air as one of the reactants in the battery, so that part of the chemistry does not contribute to the weight of the battery. That might achieve a four-fold improvement in Li theoretical specific energy, or so the federal researchers believe.

Assume some aggressive engineering and grant conventional Li batteries an eventual pack-level specific energy of 500 Wh/kg.

Multiply that by four and you get 2,000 Wh/kg for Li Air. This is a very rough and generous SWAG.

While that's certainly a big improvement and will enable larger and longer-range aircraft ops than conventional Li, it still doesn't hold a candle to Kerosene: 12,000 Wh/kg. See the problem?

I referenced pack-level specific energy because that's what you use in the real world. I *assume* the pack-level overhead for Li-Air is similar to conventional Li technology. If they can somehow dispense with some of that overhead, Li Air might plausibly do a little better. But still nowhere near kerosene.