Why battery-powered aircraft will never have significant range

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PredragVasic

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We've spent gobs on cancer research for decades and had many, many glimmers of hope. And, in fact, progress has been steady and very worthwhile. But, no single silver bullet.
The problem is, the word 'cancer' is an umbrella term for dozens of very different, and very specific diseases, in a similar way we say 'viral infection'. Viral infection can mean cold, flu, COVID, AIDS, meningitis, diarrhoea, smallpox, hepatitis, herpes, and so many other diseases, many of which have long been easily curable. Cancer is in many ways similar -- there are quite many which have long ago stopped being terminal and can be mitigated with modern medical intervention.

On the matter of battery electric flight, two components are needed: reliable and efficient motor, and reliable, efficient (and lightweight) energy storage. Motors are already there; they have in fact always been far more efficient (and far more less heavy) than comparable ICE engines. The only critical component is energy storage, and all those gobs of money and research being spent on battery storage seems to be steadily bearing fruit. For the past 20 years, electric storage technology has been steadily improving, roughly doubling every 5 - 7 years. We have almost hit the wall with the current chemistry (based on lithium), but there are other things on the horizon. There will certainly come a day for homebuilders when it will be feasible to build an RV10 and have enough battery capacity to fly it for 5 - 6 hours (and to re-charge in less than one hour afterwards).
 

Dan Thomas

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But battery technology has advanced by leaps and bounds in recent years and there's some considerable advancements being worked right now. One technology promises 10 or more times the capacity for a given weight and physical size. That would put electric cars over 1000 miles per charge with some as high as 3000 miles.
Yes, and I appreciate the lithium batteries in my drills. But we will wait for the "promised" new stuff that's ten times better. We've been promised way too many fantastic things over the years that never materialized. The fantastic stuff we have now, like that cellphone that can send you voice or pictures or videos or texts anywhere in the world, almost, was never promised like the new electric stuff (or flying cars) is being promised. If I had been told 30 years ago that I'd be carrying a tiny cellphone that could do all that and thousands more things I'd not have believed it. Too fantastic. But here it is, something we were never promised like so many other things are and have been promised that we're still waiting for.

If they do come up with batteries ten times better, very good. Electric flying will do much better than it has been, but those new batteries will also be more expensive until the patents run out.
 

Dan Thomas

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Motors are already there; they have in fact always been far more efficient (and far more less heavy) than comparable ICE engines.
Nope. Not quite. For years the most powerful motors were the series-wound things such as starters, and they were very heavy, much heavier than a two-stroke of similar power. Not until supermagnets, made with rare minerals, came available along with the massive electronics needed to drive stepping motors, did they get light and powerful.

My dad was a millwright in a sawmill. I remember the "big" motors driving the planer heads. 40 HP, and they stood three feet tall and looked to weigh at least a thousand pounds and probably more. Those were induction motors. Series-wound were somewhat more efficient but had a shorter life. They used brushes that carried huge current and wore out quickly and the commutator also wore out.
 

PredragVasic

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We've been promised way too many fantastic things over the years that never materialized.
That's the way marketing works. When you have an interesting idea and want to develop it, you need money. To convince someone who has it to give it to you, you have to promise them what you'll make with their money. And realistic promise will never get you nearly enough money to achieve what you actually want, so you go really, really big.

Current battery technology development is, in general, very closely tied to the IT industry. That explains why the claims and promises tend to be truly grand. The whole Silicon Valley startup culture is based on these outlandish projections, where each individual new software and technology solution will end all wars, eliminate hunger, poverty, end racism and domestic violence and bring prosperity to the entire world...
 

Vigilant1

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The problem is, the word 'cancer' is an umbrella term for dozens of very different, and very specific diseases, in a similar way we say 'viral infection'.
And "batteries" cover a very wide area. Nobody can say right now if the ultimate, or even the "good enough" means of storing power for electric flight will be wet chemical, dry electrolyte, bulk liquid electrolyte, super capacitors, hydrogen in matrix storage, etc.
There's a saying in finance: "Trees don't grow to the sky.' Too many investors see a trend in business or especially stock prices and extrapolate it into the future and buy in. But, there are limitations to these temporary peer/sector outperformance of stock prices and many folks who naively extrapolate short term trends to the long term get badly burned. Similarly, the gains of X% per year in lithium-based battery specific energy is no guarantee that such gains will continue, or especially that they will accelerate. Unless someone can show the specific technological pathway that will lead to electric storage equalling liquid hydrocarbon fuels, it amounts to "then a miracle happens" hand waving.
The War on Cancer (or War on Poverty, etc) is just reason to be quite wary of promises that a huge chunk of spending (especially public spending) is a sufficient condition for success.
 
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PredragVasic

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Nope. Not quite. For years the most powerful motors were the series-wound things such as starters, and they were very heavy, much heavier than a two-stroke of similar power.
I have a feeling you are talking about DC motors, which have much lower power-to-weight ratio. AC motors have noticeably greater efficiency and power-to-weight ratio than DC ones, and that has been the case for quite some time.

Current Tesla motors can deliver 193kW of output (around 260hp) and are the size of a watermelon, weighing some 70lbs (compared to an IO-520, weighing in at 420lbs).
 

PredragVasic

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There's a saying in finance: "Trees don't grow to the sky.' Too many investors see a trend in business or especially stock prices and extrapolate it into the future and buy in.
In all fairness, we have yet to see the limit to the stock market. Since its inception, when its composite value was below 100 points, to its all-time high of over 11,000, it has continuously been growing, and nothing indicates that there is a hard stop:

And back on the subject, we have no reason to expect that the storage technology for electric energy (i.e. battery) development will suddenly hit a wall. It hasn't for the past 30 years (from NiCD, to NiMH, to various lithium solutions), some other material will come along.
 

Dan Thomas

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Young physicist talks about the physical limits of batteries. Second half about the Texas wind policy.
He makes some good points. Li-Ion battery technology was developed in the 1970s but not commercialized until the '90s. Battery technology is a very slow-moving field compared to semiconductors that seem to get replaced with new stuff every two years. 5% per year advancement in battery technology, he says. I didn't watch the whole thing (hate spending an hour of my life watching something that could be read in five minutes) but the segment between the 5-minute mark and the 15-minute mark is very revealing and should be a shock to the wishful thinkers.

History. Physics. Chemistry. Really handy sometimes, really inconvenient at many more times. Reality is brutal.
 

Dan Thomas

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AC motors have noticeably greater efficiency and power-to-weight ratio than DC ones, and that has been the case for quite some time.

Current Tesla motors can deliver 193kW of output (around 260hp) and are the size of a watermelon, weighing some 70lbs (compared to an IO-520, weighing in at 420lbs).
The motors my dad had in that mill were 460 VAC 60-Hz motors. Heavy. Developed by Nikola Tesla himself. The AC motors you're talking about are a far more recent development and use variable-frequency AC generated by fancy semiconductor technology that hasn't been around all that long. Such motors have been used in the more expensive machine tools now for 20 years at least, lathes and mills that I could never afford. I'm stuck with my old belt-drive lathe from 1983 or so.

Series-wound motors will run on AC or DC.
 

Dan Thomas

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In all fairness, we have yet to see the limit to the stock market. Since its inception, when its composite value was below 100 points, to its all-time high of over 11,000, it has continuously been growing, and nothing indicates that there is a hard stop:

And back on the subject, we have no reason to expect that the storage technology for electric energy (i.e. battery) development will suddenly hit a wall. It hasn't for the past 30 years (from NiCD, to NiMH, to various lithium solutions), some other material will come along.
There's always a hard stop. You must be young enough that you haven't seen the collapse of the housing markets in 1981, or the collapse of gold and silver prices shortly after that. Not many of us will remember the great stock market crash of 1929, but it happened and a lot of people were left completely bankrupt and unemployed. More recently, the price of oil went to $170 per barrel or something like that in around 2008, driven by speculation involving the panic of that day, "peak oil." Then it went to what? $50? And five years ago it fell to $37. Tesla stock is driven by similar speculation. Almost all stocks are. Nothing magic about it at all.

NiCad batteries were first developed in 1899. It took what? 90 years before we could get them in power tools? NiMh batteries came about in 1967, 54 years ago. These things take time. Lots of time.
 

tspear

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And yet most drivers don't drive EVs and most pilots don't buy electric planes. If a pilot flies 20 times a year at less than an hour and 10 times at over an hour he meets your criteria of average flights, but he still won't buy an EV. Aircraft don't get bought by statistics. They get bought by pilots. They can and do make their buying decisions for all of their flights, not for the average. That's also applicable to car buyers. An EV would probably be fine for 90% of my trips, but I won't buy one because I still need the other 10%.
Price and fear do more to keep people away from EVs than anything else. Same thing will happen with electric planes.
And the mythical ten percent of flights or car excursions are usually more an excuse than reality. e.g. I MAY take a road trip....
Also, when buying a plane, considered the advice always pro-offered. Buy for 80% of the mission. The carry cost for the last 20% is significant.

Tim
 

tspear

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ICE engines don't break down often at all unless they're poorly maintained. Most pilots go through a whole lifetime of flying without any failures. And when failures do occur, it's usually the pilot's fault anyway. Running out of fuel or oil, mismanagement of fuel or carb ice, various things like that. An electric airplane will still need maintenance--all those electrical connections will need monitoring, as will the instrumentation, as will the cooling systems, and if they get ignored you'll have failures just like any other airplane. Aircraft, because of the terrible consequences of a failure, need far more attention than a car, and no electric airplane will get rid of that need.

The other factor here is the cost of a new electric airplane. The supply of used ones is about zilch, so you're faced with buying a new one, which eliminates about 85% of pilots right away. What's a new one? $150K? What's a used Cessna 150 or 172 or Cherokee? From $15K to maybe $75K. For $150K one could have a nice older Bonanza or 210 or a 185. A 182 certainly. Much more utilization, and likely better resale value.

And that's market forces for you. Aviation is expensive, and new airplanes are really expensive. Many pilots drive old cars so they can fly old airplanes.
ICE Engines are much more maintenance intensive. You have 2000+ moving parts in a standard ICE vehicle compared to less than 30 for an EV.
Electric connections are much easier to protect via sealing and there are many fewer connection points which need to be inspected. Also, the very nature of EV means the system can in many ways be self monitoring versus ICE where the monitoring is a separate pathway (electric sensors).
The downside of EV, many of the failure modes are yet to be understood, while with ICE they are fairly well known.

However, this is not a reason to push forward or adopt them.

Tim
 

Rhino

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I think this will be the future of electric cars first if manufacturers could standardize.The auto conversion of the future could be aircraft designed for auto batteries.
How heavy are the batteries in electric cars?
 

Rhino

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Celera 500L electric-version might look like this......280 HP MagniX motor? .......pretty exciting "disrupting-the-future", huh?
Not really. Have seen that design in several iterations. The Piaggio Avanti comes to mind, but there have been others that look nearly identical to your drawing.

...for the record: my girl-friend thinks it looks sensationally-futuristic and sexy and likes it 'cause it's smooth, quiet, and green electric...
Maybe your girlfriend thinks it's phallic. ;)

EDIT: Aha! Now I remember!

All those topless men may make your girlfriend think it's sexy too. Kinda blows holes in the "sensationally-futuristic" theory though.
 
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Rhino

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Price and fear do more to keep people away from EVs than anything else. Same thing will happen with electric planes.
And the mythical ten percent of flights or car excursions are usually more an excuse than reality. e.g. I MAY take a road trip....
Maybe you speak for the locals in Oneida, but I've hardly ever met anyone who doesn't ever make road trips in their automobiles. That's probably less than 1% of the people I've met, and I've lived or travelled over most of the planet. Granted, some don't make those trips very often, and it can vary to some degree in other countries and urban areas, but they do make them. And they won't spend their money on cars that don't have that ability, even if they never actually manage to make such trips (those that MAY take a road trip). That's pretty much what we're seeing with the relatively low demand for EVs at this time. So this isn't even remotely a myth. Keep in mind also that this isn't limited just to long trips. People who want to make frequent and/or repeated trips in their local areas will have the same concerns and hesitation.

Also, when buying a plane, considered the advice always pro-offered. Buy for 80% of the mission. The carry cost for the last 20% is significant.
Ah, but this time the cost for the last 20% may well be cheaper considering the cost of buying a new electric plane. If the price of ICE aircraft falls due to a market shift to electric, and/or if their operating costs rise, selling or trading their ICE plane will garner them much less money to put down on a new electric plane. Also, many of them already have that last 20% of capability with the aircraft they own now, so that isn't a sufficient motivator for them. You also have to take into consideration that buying a plane for the 80% doesn't necessarily exclude the other 20. I chose my aircraft for the 80 to 90 percent of local, low and slow flying, but it doesn't mean my plane won't do that other 10 or 20 percent. It just isn't the optimal choice for that segment. It will still accomplish every mission I want it to. It just does some missions a lot better than others. You could argue that waiting hours, or even overnight, for a battery recharge on cross country flights, means the same sort of compromise, but my plane can still be in the air during those periods even if it isn't the best cross country aircraft out there. A pilot will generally prefer to be in the air rather than on the ground during a cross country trip, even if it means going slower or spending a little more in cost of operation. Remember that people don't become pilots thinking that flying is cheap, so they've for a large part acquired a grudging expectation of high operating costs.

It really doesn't matter if their motivation is an excuse, a fear, a misperception, or is completely valid. The market is fickle, predicting it even more so, and one can't logically depend on everyone else seeing the same advantages that they see. We've seen that time and again. Investors know that, and it's largely their choices that will determine how 'mainstream' the replacement of ICE aircraft with electric aircraft becomes, when the trend starts in earnest, and a what rate that trend accelerates once started.

ICE Engines are much more maintenance intensive. You have 2000+ moving parts in a standard ICE vehicle compared to less than 30 for an EV.
Electric connections are much easier to protect via sealing and there are many fewer connection points which need to be inspected. Also, the very nature of EV means the system can in many ways be self monitoring versus ICE where the monitoring is a separate pathway (electric sensors).
The downside of EV, many of the failure modes are yet to be understood, while with ICE they are fairly well known.
Those are all very good points, and important ones that will help drive consumer choices as well. Obviously failure modes may vary as new technologies develop, but I think you'll always have fewer failure points with electric propulsion. Less maintenance and simpler inspections will likely always be an advantage of electric propulsion over ICE.

However, this is not a reason to push forward or adopt them.
I assume you meant this is not a reason to not push forward. I agree we should definitely push forward. Many of the original obstacles to electric propulsion have been overcome by technological advancement, and many more are bound to be overcome as such R & D continues.
 
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Geraldc

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How heavy are the batteries in electric cars?
Tesla batteries weigh 6kg per kwh
Pipistrel uses two replaceable battery packs weighing 58 kg each
to give 21 kwh.
So about the same.
edited misread Pipistrel specs
 
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