UdoR wrote:
Empty mass is 900 kg, so removing the engine (200/900) reduces mass by 22%.
It’s not the mass of the engine as a proportion of empty mass that matters, it’s the mass of the engine as a proportion of MTOW. That’s where the gain (or relatively, lack of gain) lies.
Your proportion is 200kg / 1600kg = 12.5%. The higher the mass of the engine as a proportion of MTOW, the greater the proportion of MTOW available for batteries in the electric equivalent.
The other issue of course is that trading fuel for payload, as is very common in GA, is much more difficult with batteries than with liquid fuel. So your statement about your numbers being full-fuel payload doesn’t mean much, because for an electric aircraft available payload is (presently) fixed regardless of endurance.
UdoR wrote:
If I went for a minimum of 100kg payload, I could install 700 (or 800) kg of batteries.
Now we have a 1600kg aircraft with one seat and space for your suitcase? It’s probably possible to make something the size, shape and weight of a Comanche that’s battery powered and will do 130KTAS for a few hours, but an enormous proportion of that 1600kg will have to be batteries and you’d barely be able to carry the pilot. It just wouldn’t be a useful product, not in comparison to the avgas equivalent.
UdoR wrote:
So a rough estimation sounds like some 5 hours of endurance could be achieved flying about 130 KIAS (which should be independent of altitude, so a flight in the low flight levels would be reasonably possible).
Perhaps if it were that simple someone would have done it.
UdoR wrote:
That should give result in a significant range.
A lot is possible. The problem is people look at everything that is NOT possible (like flying nonstop across the Atlantic at MACH 0.8) and extrapolate from there, ending up with the conclusion that power density absolutely needs to increase by a factor 10-20.
The eFlyer with it’s 3h “cruising” endurance and 20 min charging time will do just fine for training. From the video, one such airplane will cost about $500k, the same as a C-172. The operating costs however will be 1/5. Now, that alone opens up possibilities that are literally impossible with a traditional aircraft. It’s the same for EVs. It will not be the environmental concerns, super long endurance due to some new battery technology, insane amount of power or any other technical stuff that will cause a shift. It will be the economy. EVs will be cheaper to operate, already is today at many places. When this happens on a general scale, then that’s that. There will be no more cars with combustion engines.
The curve showing dollars per kWh for batteries the last decade:
When I bought my first EV in 2014 the cost was 592 $ per kWh. Last year it was 137. This will only continue to decrease in the foreseeable future. This continuous decrease is all that is needed. Power density will only slightly improve, and has a physical limit for any given technology:
LeSving wrote:
The eFlyer with it’s 3h “cruising” endurance and 20 min charging time will do just fine for training.
That aeroplane does not exist. It’s based on a fantasy battery supplying a particular amount of power at a size and weight that are a long way from anything that’s possible now.
Even if it did, what phenomenal power supply would be required to charge it in 20 minutes?
These ‘products’ you keep watching videos about are not real. They’re concepts, which would work if the fundamental challenge related to the energy density of a battery could be solved. Again I point you to the concept of assume a can opener.
Wonderful engineers and innovators have solved most of the challenges related to electric aeroplanes. What is left to solve is no different to the challenge of designing an avgas aeroplane in an imaginary universe where avgas weighs 4-5kg per litre.
Graham wrote:
That aeroplane does not exist
I touched it at Oskosh in 2016 
But that was probably eFlyer 1, not sure. It surely do exist. What does not exist is the bureaucracy enabling it to be used on the same terms as traditional aircraft. Not yet at least. That has very little to do with the technology however.
This is a picture from 2016, it was called Sun Flyer then
Yes; those mockups are seen every year at Aero Friedrichshafen
The place is full of them. They are a good fit for the “modern society psyche” and earn lots of brownie points for the exhibitors who now look really eco-friendly
FWIW I bumped into a UK Power Networks guy this morning. He was looking for a transformer so I showed him He debunked the “min 1k/month rental charge for 3 phase” (there is no extra charge for up to 100A per phase i.e. almost 70kW) but said that the minimum installation cost would be 3k-5k. They also require the meter to be outdoors so you have to build a “little house” for it, or a box on the outside of the house.
Have not read all 107 pages of this thread but I was thinking about possible battery fire. If that happens in the air what then?
A few days ago the fire department was called out to a hybrid Peugeot on fire here in DK. It was the battery. They had to call a special truck with a container filled with water. A crane lifted the car up and into the water. I guess our standard GA fire extinguisher won’t do the job…
Peter wrote:
Yes; those mockups are seen every year at Aero Friedrichshafen
Nice mockup then, et even flyes
Peter wrote:
but said that the minimum installation cost would be 3k-5k
Here you get chargers for free when purchasing an EV I haven’t used that opportunity because charging from “the wall” is more than enough for everyday use, even if it takes a day and a night and then some from zero to full. For longer trips you visit DC fast chargers anyway. In other words, 70 kW home charging is a waste of money. 16A or 11A will do just fine.
Oh plenty of the prototypes fly, but not for any useful length of time.
Graham wrote:
The other issue of course is that trading fuel for payload, as is very common in GA, is much more difficult with batteries than with liquid fuel. So your statement about your numbers being full-fuel payload doesn’t mean much
One should take into account, that it is in fact possible to put batteries in the cabin depending on the needs for payload. This had been presented in microlights, where you have 1 hour endurance with 2 POB but up to 3 hours with only 1 POB by putting a battery on the second seat. So my argument about “full fuel payload” is directed towards that you just don’t have to take into account additional liquids as we do have now.
If you take an existing airframe it might be more difficult to remove or install additional batteries, because it’s just not designed for this. But introducing some opening for this purpose, in the end, will not be the problem.
Graham wrote:
it’s the mass of the engine as a proportion of MTOW
But not only the engine has to be taken into account, also the fuel, at least part of it. It’s another story if your aircraft can haul a lot of fuel, which translates into high available payloads. You can easily add two hours of fuel to the possible weight for battery installation, because you will depart only on very few occasions with less than 2 hours of fuel on board.
Graham wrote:
Now we have a 1600kg aircraft with one seat and space for your suitcase? It’s probably possible to make something the size, shape and weight of a Comanche that’s battery powered and will do 130KTAS for a few hours, but an enormous proportion of that 1600kg will have to be batteries and you’d barely be able to carry the pilot. It just wouldn’t be a useful product
I think of it another way, taking into account that some of the batteries should be (re)movable. And I really don’t get it, why this should be regarded any different than what we actually do with our planes today. There are so many planes around which – with full fuel – are two-seaters or even single-seaters. So if I want to have max. range, then I add batteries and trade payload for range.
And I say again: lots of people would be totally satisfied to have 250kg of payload in a SEP, because this is what is absolutely comparable to a lot of SEPs around today. I, too, would be fine with 250kg, taking into account that I typically load an additional 300kg of fuel into my plane.
So this still leaves 700kg of room for installation of an electrical engine and a lot of batteries…
