Vstol might help – electrical systems have a very high power density which makes it more achievable, and the ability to land in small spaces could help cut down on reserves required.
RikB wrote:
If I look at my smartphone/tablet/laptop it is always unclear how long the battery last.
That’s mainly because power consumption changes all the time. Also, I bet the phone doesn’t manage its battery half as well as an electric aircraft would.
RikB wrote:
If I look at my smartphone/tablet/laptop it is always unclear how long the battery last.
A smartphone is not an electric vehicle. An EV is very good at “predicting” the remaining battery. The battery is typically kept within a certain temperature range by a heat pump. What is more difficult is guessing how and where the driver decides to drive 
For an aircraft I don’t see that factor as a particular difficult factor, it’s mostly an operational constraint that has to be investigated and solved operationally.
It’s obvious that electric aircraft is in it’s early infancy. The requires thinking in new terms, not in old terms. In particular, suggesting this and that cannot be done by pointing to existing limitations and constraints for old technology is useless. It reminds me of an ancient joke: What would we do if the ocean disappeared? Then we would have to carry the boats.
Isn’t it inherently impossible to know the energy left in a battery, accurately?
This is a chestnut so many have tried to crack, for decades, and without success. Best methods are integrating energy in and out, and temperature compensating as you go along, using sensors distributed throughout the battery pack. And then temperature-adjusting the result for the current battery temperature (which starts off as the OAT). A lot of electric cars lose a fair bit there in real life because the battery never gets warm enough, and using the battery to heat itself is obviously daft, beyond a certain (small) point.
Still the only “solutions” I know of involved setting aside say 20-30% and calling that point the “zero level”. I would bet this is what they do in electric vehicles.
And not just for the “capacity reporting reason”; they need to hide customer-obvious signs of battery degradation. Let’s say you can accurately measure the degradation from one month to the next. “You” are going to post in on every forum there is! And there will be many; just in the UK there are four forums for the VW Scirocco This has the potential to make one particular maker’s battery look worse than another’s, simply because they are applying different criteria. The whole “battery life” thing is a hot potato anyway, because the battery is a big chunk of the cost of the car.
@Mark_1 may know more about the latest tech.
Yesterday I bumped into some Power Networks guys doing a cable in the road so I asked them about 3 phase to our house. They said it is not available anymore unless you pay the industrial tariff which is £1000/month. I find that hard to believe because in my previous house (my ex lives there now) 3-ph costs nothing extra. The installation would be a few k but that’s to be expected. If true, it is a PITA because single phase is limited to about 20kW. It is also a poor solution for anything with a big motor e.g. a heat pump.
Still the only “solutions” I know of involved setting aside say 20-30% and calling that point the “zero level”. I would bet this is what they do in electric vehicles.
Apparently the battery is kept above 10% empty at all times and below 90% at all times. 10% is zero and 90% is max. Could be 15 or 20% for all I know. The reason is that the batteries degrades fast if they are discharged to min and charged to max. Experience shows that the typical EV battery lasts for many hundred thousands km. Much longer than the car itself will normally run.
This is not done in phones for instance, and as a result, the battery wears out in a few years time.
I would think this keeps the battery healthy, and therefore much easier to predict compared with the battery in a phone.
So far the car producers obviously have been conservative regarding battery life. With more experience they are bound to stretch the rubber band more of course. In a certified aircraft this should be a no-issue (or else certification has no value).
Most batteries also last longer if you avoid charging and discharging to the extremes. In a car or phone you protect the battery by preventing the operator from draining it fully. In an aircraft you might hope the designers will allow the operator to use the last few percent, if they really need to.
Edit, written at the same time as LeSving.
Airborne_Again wrote:
I would also be uncomfortable, but primarily because I would not be sure I really has 1h30 endurance. Exactly how much fuel is in the tanks? (In this case a few litres more or less makes a big difference.) Exactly what is the fuel consumption? (You may have a fuel totaliser, of course.)
You don’t need a fuel totaliser to know what you’ve got on board, you just need to establish it before you take off.
In the case of the PA17 I can fuel plan with perfectly sufficient accuracy without any fancy equipment, and predict my range/endurance with far greater accuracy and consistency than any EV. I know the tank holds 45 litres and I know it is full because I’ve looked. I know it burns 18 litres an hour at my usual cruise setting, and that is accurate (determined experimentally by topping off the tank post-flight) to 1 litre either way. I thus know that 2hrs is my maximum planned airborne time, after that I am on my reserve and frankly I would prefer to have an hour’s reserve rather than half an hour. If I found myself needing to use it I would likely throttle back to a speed closer to best-glide and get a bit more range/endurance.
The PA17 with 2hrs planned airborne and 30 mins reserve is really quite a limiting aircraft in terms of going places. Regardless of liquid fuel or battery, an aeroplane with a ~1hr endurance is going to be less useful, not more.
It’s not a question of how it’s powered. It’s a question of range, and the fact any flight needs fuel reserves. @Peter frequently reports his fuel planning and consumption accurate to within 1%, and no battery management system is going to better that. Even if it did, you don’t want aircraft landing with 10 mins endurance remaining – no matter how certain you are of those 10 minutes.
Graham wrote:
You don’t need a fuel totaliser to know what you’ve got on board, you just need to establish it before you take off.
I wrote that you need a fuel totaliser (or simply a fuel flow meter) to know the consumption.
Airborne_Again wrote:
I wrote that you need a fuel totaliser (or simply a fuel flow meter) to know the consumption.
And indeed you do not. In both the TB10 and the PA17 I know the consumption to the degree of accuracy necessary for fuel planning, and neither has a totaliser or a flow meter. Having one and seeing the exact burn might be interesting, but it would not alter my fuel planning nor lead to getting more range out of the aircraft.
Graham wrote:
Regardless of liquid fuel or battery, an aeroplane with a ~1hr endurance is going to be less useful, not more.
I don’t know what the range is of a dash 8 -100/200s that Widerøe use, but I guess it’s a whole lot more than 1 h. The range of that Tecnam they are presumably going to investigate could be 2h for all I know. It could have a range extender also. Nothing is known about it, it will not fly for some time yet, if at all.
However, some of the routes are only 20-30 minutes. If the thing materializes, I would guess it would be used on shuttle traffic on such a route, just to test it out. The way they fly today is long flights doing several stops, they obviously cannot do that with 1h range. 1h range if the flight is only 20 minutes, why not? It certainly is technically and operationally doable. The fuel costs will plummet, but will it really work? Only one way to find out.
