My Nissan Leaf Forum

WetEV wrote: ↑

Wed May 27, 2020 6:56 am

Looks like I was incorrect, thanks for checking. There is less potential for improvement that I suggested.
Adding in the air mass is fairly easy. And I didn't do it.

https://en.wikipedia.org/wiki/Stoichiom ... mmon_fuels

13000Wh/kg/14.7 = 880 Wh/kg (gasoline air) or about 5x times for gasoline-oxygen or 4200Wh/kg as air is 21% oxygen.

So 16x today's batteries is about the limit. Not 50x. Practical limit is less, perhaps 4x. So a range of 1200 miles is about the best we could hope for. 12 hours at 100 miles per hour. Can anyone's brain, butt or bladder last that long?

Nubo wrote: ↑

Wed May 27, 2020 11:09 am

why is the mass of air important for comparing gravimetric energy density of fuels? The car doesn't have to carry that mass around.
how does the energy density of gasoline dictate a limit for the energy density of an electrical storage device?

Both provides an idea as to the actual mass to energy ratio possible. Rough, sure. Batteries are unlikely to exceed something like gasoline/oxygen or even gasoline/air.

Nubo wrote: ↑

Wed May 27, 2020 11:09 am

Not sure I understand. First of all, why is the mass of air important for comparing gravimetric energy density of fuels? The car doesn't have to carry that mass around. Second, how does the energy density of gasoline dictate a limit for the energy density of an electrical storage device?

coleafrado wrote: ↑

Wed May 27, 2020 4:46 pm

Nubo wrote: ↑

Wed May 27, 2020 11:09 am

Not sure I understand. First of all, why is the mass of air important for comparing gravimetric energy density of fuels? The car doesn't have to carry that mass around. Second, how does the energy density of gasoline dictate a limit for the energy density of an electrical storage device?

- It isn't
- Correct
- It doesn't.

The air mass thing was a red herring. (unless we can get air-breathing batteries, which I personally don't think will happen within the next 50-100 years.)

WetEV wrote: ↑

Thu May 28, 2020 6:39 am

There are "air-breathing batteries" now.

https://en.wikipedia.org/wiki/Aluminium ... ir_battery

These are primary batteries, IE non-rechargeable, but putting in fresh aluminum and removing the oxidized aluminum has been both proposed and demonstrated, along with 1300 mile range.

Yes, kids, you can do this at home!

http://exo.net/~pauld/activities/AlAirB ... ttery.html

coleafrado wrote: ↑

Thu May 28, 2020 8:49 am

WetEV wrote: ↑

Thu May 28, 2020 6:39 am

There are "air-breathing batteries" now.

https://en.wikipedia.org/wiki/Aluminium ... ir_battery

These are primary batteries, IE non-rechargeable, but putting in fresh aluminum and removing the oxidized aluminum has been both proposed and demonstrated, along with 1300 mile range.

Yes, kids, you can do this at home!

http://exo.net/~pauld/activities/AlAirB ... ttery.html

Speaking practically, I don't see anyone loading their cars with vacuum-sealed aluminum-air batteries any time soon. They beat NiMH and lead-acid any day, but they're not competitive with lithium-ion.

Wikipedia wrote:Aluminium–air batteries (Al–air batteries) produce electricity from the reaction of oxygen in the air with aluminium.

coleafrado wrote: ↑

Thu May 28, 2020 1:27 pm

Vacuum sealing before use is necessary to prevent self-discharge. Some have claimed that it's no longer necessary - at the scale of automotive batteries, that's hard to believe. Do you have any idea how physically and mentally inconvenient it would be to manage a fleet of batteries (each 50-100 kg and costing hundreds of dollars) at various states of discharge just so you can drive around? Completely ridiculous. What works for a watch or a calculator does not work for a car. Maybe rechargeable metal-air batteries will work, eventually. Nonrechargeable cells will never be used for EVs.

LeftieBiker wrote: ↑

Fri May 29, 2020 1:54 pm

I remember an aluminum-air prototype car back in the Nineties. The discharge output was so low that they needed to add a smaller Ni-Cad pack just so the car could accelerate on the highway. They had more luck with a bus, again, IIRC, with a second pack for acceleration. The aluminum modules had to be replaced regularly as they were exhausted.