Why battery-powered aircraft will never have significant range

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Dan Thomas

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The public wants safe, affordable transportation, whether it's on the ground or in the air or on the water. They don't want a vehicle of any sort that has a short range and takes a long time to fill up or recharge. Basically, they generally don't want anything that isn't as capable as what they have now.

A few will buy them, thinking they're doing their part in reducing CO2 emissions, but they are also the sort that don't know the real numbers---that some large countries talk a good line on reducing emissions but keep building thousands more coal-fired powerplants, making any of our sacrifices completely useless. Nothing will change on that front. These countries want all the same goodies and standard of living that we do, and they're using the same technologies we used to achieve that. If we don't develop safe, reliable and efficient nuclear plants, they aren't likely to do it either. We have to lead the way on that, and therefore someone needs to get out of the way.

Or we just go back to the 1850s. There isn't much choice, is there?
 

Aesquire

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Cover article Kitplanes... eXenos motor glider!

I'll ignore the politics and utopian promises. :)

That cute copter back pack. The human dronelike multi copters, are electric because that's the current ( bad pun ) technology for the computer stability systems.
 

raumzeit

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FAR103 regulations make electrics interesting possibility in that space. Electric motors have such a higher power density to weight makes them possibly competitive given fixed install weight of even tiny ICE engine. If FAR103 interpretations let electric plane count batteries as "fuel" up to, say, 18kgs or so akin to same mass in five gallons of petrol, ICE engines would really have run for their money in that space given the artificial cap on fuel.
 

Victor Bravo

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Part of my "day job" is being able to make a legitimate sounding case for or against almost anything. So (myself and many others here) could easily make a case for or against the idea of electric flight being in worldwide use tomorrow. Or we could just as soon explain why it is too far into the future.

As with almost everything in the universe, hope and reason and history and technology and desire and money and whatever all has to be in balance.

Very shortly after I was born, the President famously said that we would land a man on the moon "this decade", and we did it. How many sarcastic pundits and barbershop philosophers around the world said that he was totally off his rocker, and we'd never accomplish that in 50 years much less 8 or 9? But when I was a child, sure enough we landed someone on the Moon. The scientists and engineers figured out how to do it, the generals and military strategists knew we needed to do it, and our entire country wanted to do it and paid for it to get done.

When I was in elementary school, the dashing Captain of a spaceship came on TV every week, and did a bunch of things that we would NEVER be able to do.... He talked to his friends on a flip phone that fit in his pocket, he had a little gun that would temporarily stun attackers but not kill them, he could see and talk to other spaceship captains in real time on a big screen, he could talk to his computer by just saying "Computer", and it would translate a hundred alien languages into English for him. The only thing that he could do that I still can't do now is transport himself somewhere through a beam.

Around the same time, I went to a magical place called the Cinerama Dome in Hollywood, and saw absolute undeniable proof that space travel was possible. I learned that space stations were technically feasible, and that when you went to a space station the most intense and emotional waltz music would play really loud in your head, and you would remember that moment for the rest of your life. I learned that you could make a video telephone call all the way from space to talk to your daughter, and you could even go to the bathroom in space if you read the instructions. I learned that computers were really smart, but they also had the possibility of watching you and listening to you when you didn't think they would. I learned the computer could even get angry and do a lot of harm, and sometimes it wouldn't even open the door no matter mow many times you asked, so you'd have to physically unplug it. Back then, an awful lot of old people reassured me that we'd never see that kind of world in our lifetimes.

So as much as many of us really enjoy poking holes in electric powered airplanes, and as much as we love to joke about 60 years of hype, history shows us that science fiction often does become reality.
 

blane.c

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It isn't that electric airplanes are economically the choice at this time, it isn't that with experimentation that they will be the economical choice in the future because we don't know the future, it is that without experimentation and experimenters we may never know if it they can be. Without experimentation there is only ignorance and tyranny.
 

Dan Thomas

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It isn't that electric airplanes are economically the choice at this time, it isn't that with experimentation that they will be the economical choice in the future because we don't know the future, it is that without experimentation and experimenters we may never know if it they can be. Without experimentation there is only ignorance and tyranny.
The old experimenters used existing technology and adapted it to airplanes. I don't think any of them invented a new technology. Ken Rand adapted model airplane styrofoam and epoxy procedures to homebuilts and started the composite revolution. Burt Rutan took an old idea--the canard--and modernized it. (The Wright Flyer was a canard, sort of.) Almost everyone used either existing aircraft engines or adapted existing car or motorcycle or marine engines. The electric airplane needs NEW technology that doesn't exist yet: safe batteries with massive storage capacity, and those aren't likely to happen in someone's garage or basement. The chemistry is too complex. In fact, I think the answer will come in the form of something rather different from what we see now.
 

EzyBuildWing

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Luminati Coaxial electric heli development.....what the heck happened to these guys since this vid? Anyone know???
Certainly had a large battery-pack....
Maybe they're waiting for the new "Kryptonite" battery to appear?

 

Aesquire

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Electric motors have such a higher power density to weight makes them possibly competitive given fixed install weight of even tiny ICE engine.
True, but you are missing the weight of the fuel. The motor, or engine, consumes stored energy & turns it into motion, via the prop(s), So you need to figure the mass of both motor and energy storage.
 

tspear

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You brought up C172 in post 1441. What model is it?
I have heard of four students in a C172. They observe from the rear seat. I don't know if they can log the rear seat time.
No you cannot log that time in the backseat for primary instruction. It can count as class time for some part 61 schools, but I do not know the rules (or care enough to look them up).

I should have been more specific in my first post. Yes, the Electro can replace the C172 or C152 for majority of the paying public for some aspects of flight training.
Is that better? :)

Tim
 
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tspear

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We have learned - through long, long experience - that those sorts of "expectations" are meaningless. So nowadays when I hear things like that the credibility of the speaker drops to zero.

Snake Oil Salesman.

IF and WHEN battery back endurance doubles - without sacrificing elsewhere - then let's see what that does for the viability, usability and marketability of electric airplanes.
Cynic :)
In this all cases, you should look at the history of the speaker. The Pipistrel CEO has been very careful with his promises and comments from what i have seen/read. In this case, based on other articles, I think the CEO is correct. The reason is Pipistrel specifically picked an older battery chemistry to lower cost and risk while they worked other issues. Based on these comments, they are now working on tackling the battery with a more recent technology.
The current battery pack is 21kwh and 53kg. That about 0.4kwh per kilo. That is abysmally low.

Tim
 

Saville

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Cynic :)
In this all cases, you should look at the history of the speaker. The Pipistrel CEO has been very careful with his promises and comments from what i have seen/read. In this case, based on other articles, I think the CEO is correct. The reason is Pipistrel specifically picked an older battery chemistry to lower cost and risk while they worked other issues. Based on these comments, they are now working on tackling the battery with a more recent technology.
The current battery pack is 21kwh and 53kg. That about 0.4kwh per kilo. That is abysmally low.

Tim

Haven't got the time to research the historical utterings of the speakers.

Which is why, on this topic, I write that I wish them well but will believe it when I see it and when the market buys it.
 

PiperCruisin

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The current battery pack is 21kwh and 53kg. That about 0.4kwh per kilo. That is abysmally low.
Looking on their website, they listed a battery with a nominal voltage of 345V and 30Ah and 72 kg. This works out to about 144 Wh/kg. In our application we use about 180. The current technology is around 250 if you push it. There are lots of news looking at 400-500 Wh/kg. So, if they went from 144 to 400, that would be quite a change and starts to get interesting. I'm guessing we'll get in the 500 Wh/kg range, but after that, who knows. Would probably require some big breakthroughs. Still not quite in the range that is practical to us unless we're talking ultralights and self-launch gliders, or short duration trainers.

Otherwise, with all the electrified stuff out there (cars, motorcycles, lawn mowers, busses, locomotives, drills, etc.), it's not like we're starting from scratch or alone in this endeavor. With about 500 designs (in eVTOL news), some flying, a crazy amount of money and effort (from some big names) is going into it.
 

tspear

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Looking on their website, they listed a battery with a nominal voltage of 345V and 30Ah and 72 kg. This works out to about 144 Wh/kg. In our application we use about 180. The current technology is around 250 if you push it. There are lots of news looking at 400-500 Wh/kg. So, if they went from 144 to 400, that would be quite a change and starts to get interesting. I'm guessing we'll get in the 500 Wh/kg range, but after that, who knows. Would probably require some big breakthroughs. Still not quite in the range that is practical to us unless we're talking ultralights and self-launch gliders, or short duration trainers.

Otherwise, with all the electrified stuff out there (cars, motorcycles, lawn mowers, busses, locomotives, drills, etc.), it's not like we're starting from scratch or alone in this endeavor. With about 500 designs (in eVTOL news), some flying, a crazy amount of money and effort (from some big names) is going into it.
I trust your math more than mine at in morning, especially before caffeine!
If they are really at 144, getting to 288 in the next few years sounds very doable with just a 2% increase a year from 250.

Tim
 

Aesquire

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eXenos uses a Zero Motorcycle motor, battery, and electronics. Builder purchased a partially built kit ( with countersunk rivets! Nice job ) and used the landing gear portion of the engine mount, cut off engine bits & built the battery mount to fit firewall forward. Oh, and the motor's mounted there, too. :) Weight & balance lucked out!

Some custom programming, no fuel tank, minimal alterations to cowl, even used the motorcycle bar switch module, a very clean ( & still in progress, fairings, etc. to come ) and logical conversion. Firewall forward kit to come soon. Since there's no structural alterations to the airframe other than firewall forward battery mount,the nice folk at Sonex won't ignore you. ( which they would be totally justified if you were installing a 300 hp Continental )

The prototype has roughly "a little under an hour" endurance under power, but that will improve with further clean up of the airframe and change of the PSRU ratio. NIce! BUT! That's not full throttle operation. Much of the article's magazine demo flight was slow flight down near 60-ish to simulate infinite glide angle and allow soaring on any rising air. ( a hilarious cheater soaring technique, making a marginal motor glider outperform the best carbon supership... Kinda. ) Speed takes power, so I'd guess that near hour endurance is down at speeds where the regular IC engines would be throttled back to stretch time in flight. ( but not as low as the article's "just enough to maintain altitude" power )

This looks like the closest yet to a "practical" homebuilt electric. I like the looks of the Pipistrels, but the Sonex line has a longer history and sheet metal... I will point out that while the upcoming firewall forward conversion may be easy to install on the short wing Sonex & Waiex, endurance will be less because of higher speeds.

And in further news... California has announced they want everyone to help with the power crisis caused by... Summer... And government power policy... by doing a number of logical lifestyle changes to reduce peak power consumption. ( and the massive load on the power lines feeding from out of state ) Tips like pre-cooling your house off peak, and not charging your electric car when you get home in late afternoon on the typical person schedule and demand spikes. They even have a handy posted time and cute buzzwords for what certainly isn't rationing, and in no way reflects on decisions made for decades in Sacramento.

Admittedly, California is atypical. :)

But it does emphasize a statement made here, repeatedly, that conversion of a society 's vehicle fleet from IC to batteries requires a build up of grid power generation, or it. won't. work.
 

tspear

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And in further news... California has announced they want everyone to help with the power crisis caused by... Summer... And government power policy... by doing a number of logical lifestyle changes to reduce peak power consumption. ( and the massive load on the power lines feeding from out of state ) Tips like pre-cooling your house off peak, and not charging your electric car when you get home in late afternoon on the typical person schedule and demand spikes. They even have a handy posted time and cute buzzwords for what certainly isn't rationing, and in no way reflects on decisions made for decades in Sacramento.

Admittedly, California is atypical. :)

But it does emphasize a statement made here, repeatedly, that conversion of a society 's vehicle fleet from IC to batteries requires a build up of grid power generation, or it. won't. work.
That requires a change in social behavior. And time of use metering, along with well established demand management timers to accomplish.
I was considering an EV a while back, and the charger I was looking at had a timer to delay charging to a specific start time unless a overrode it.

Pretty simple stuff.

Tim
 

Rhino

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That requires a change in social behavior...
In Kalifornia it requires a change in something else, but we aren't allowed to discuss politics.

I do wonder where they think the power will come from for all these electric cars when they can't even manage enough power to keep the lights on in the summer.
 

PMD

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I guess why I am so disgusted in electric cars, boats and especially planes is that experimentation is usually to try to make things better, not compound making virtually EVERYTHING worse - utility, environmental impact, sustainability, resource use, safety, etc. The Euroweenies have sucked us into a virtue signalling shythole, and so many have simply followed them right into the toilet.
 
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