Depends on what you mean by "fix" and what you mean by "ever".Google "energy density" of batteries vs. gasoline. It's a hard physical limit, not something that "better batteries" can ever fix.
So, 5 gallons is 35 pounds, ( I'm using 7 pound per gallon ) and 1/6 the battery is 500 pounds. Take away 100 pound for a realistic V-twin 4 stroke & add 35 pounds for a realistic motor & controller.I believe someone took numbers for an RV3. 30 gallons of gas about 180 pounds of fuel. Batteries, 3000 pounds. That's on top of the 1200 lb airplane. One for one it's not close to doable with range of gas. Just getting in the air for 15 min is doable.
Wish I had the answer to that. However, I had the pleasure of spending a couple of days @ the "Battery Expo" in Novi MI 2 weeks ago. 600 vendors of all stripes their to showcase their products in relationship to electric mobility. This is electrification of drive-trains is not going away folks, it is real, people attended from all over the world, and words do not do a trade show like this justice until you see it for yourself or attend some of the seminars. This year what a struck a chord with me was the vendors showcasing what you might consider mundane sub-components that would reduce vibration, temperature, or in one case let the current flow w/ less resistance via a winding type. All geared towards increasing driveline efficiencies in total around the margins. I don't want to get too in the weeds, I have an article I have to rap up on this show. However, does a 40+ lb 200 hp motor that would fit behind an RV spinner grab your attention that will be in a flight application in the near future, or a Solid State battery that will find it's way into the UAV space in 19'. Yes power densities are up in this space, and will be even more so w/ Solid State. Are we there yet? Not to the point of the RV-3 total replacement needs mentioned in this thread, I can't refute the math or the physics. I am curious as to how close we are to your typical $100 hamburg special aka fly out 1 hr away with your buddies in formation, and your bird charging while you are refueling .. Add your low-drag favorite 2 seater that might be amenable to this type of retrofit and imagine what the retrofit might look like or entail. The Gent here on HBA w/ the E-Belite might give us some data points soon, probably not far off from Mark Bierle's efforts. Anyway I look forward to hearing on all of these experimenters progress and wish them well.How far off from hp/running time are electric powered craft vs gasoline powered.
No, you'd only need about 18ish kW. But higher capacity cells than 3Ah are only good for 1/2 the current, so you'd have less than 18kW with a your lighter pack with less cells. Inadequate. Running cells at their max ratings isn't great for life. Considering what you'd spend on a pack, you probably want to consider life.For 20 hp, you wouldn't need anywhere near 36kW. Maybe half that. For high specific power, some guy on eBay has been selling big packs of maybe 96 A124 cells, formerly used by the Navy. One cell is good for 60 amps when new.
I have been contemplating a similar calculation recently. Fuel tanks and fuel have a lower energy density than batteries - fact. But it is possible to get higher energy conversion density out of an electric motor. So where is the sweet spot? At what engine power and duration does there exist a point where the (starting) mass of the propulsion system is the same for IC as electric? (The answer might be there is no such point)Depends on what you mean by "fix" and what you mean by "ever".
Yes, gasoline is always going to have more energy density than a battery as we know them. However,batteries are improving. Also, electric motors are much more efficient and lighter. Let's take a look at the kind of ultralight I think about, meant for motorgliding. Say it needs to have about 20 hp for takeoff, 6 hp for just flying around. Say we're going to cruise around for an hour. 5 minutes of 20 hp followed by 55 minutes of 6 hp. 1 hp hour is about 2.7 MJ. Total of about 19.4 MJ.
Let's say I'm using a 4 stroke with redrive, that weighs 60 lbs and uses 0.4lbs/hp-hr or about .15 lbs/MJ. That's only about 2.9 lbs of fuel for our 19.4 MJ! Maybe it's a bit optimistic, but we'll stay with it. We probably need a 5 lb gas tank, so now we've got 68 lbs.
A couple of brushless motors that give about the same power, from t-motor, weigh only about 7 lbs. (And, don't forget, the motor mounts will be lighter for the electrics. But maybe that's diminished by having to support heavy batteries. ) ESC weight is less than a pound! According to Wikipedia, lithium batteries are around 1.8 MJ/kg, and the motor efficiency might be 85 percent. Works out to 28 lbs of batteries and a total of only 36 lbs!
Of course, with a two stroke maybe we have 25 lbs of engine and redrive, a 5 lb tank, and 4 lbs or so of fuel and oil, for a total of 34 lbs.
So for a really efficient ultralight the electric power is almost as light as a two stroke for 1 hour flights. Add a bit of drag or weight, and it's likely the break even point is as low as 10 or 15 minutes. But a big improvement in batteries could stretch that out to a much longer time.
To tell the truth, I expected the batteries to do a bit worse than this.
If I've screwed up the calculations or assumptions, please point it out. Maybe I could pull some numbers for real batteries and see if the figures agree.
Well, there's more things to figure than just hp/running time. At it's Simplest form, say for a Part 103 Ultralight.How far off from hp/running time are electric powered craft vs gasoline powered.
A123's were my suggestion for a hybrid system.No, you'd only need about 18ish kW. But higher capacity cells than 3Ah are only good for 1/2 the current, so you'd have less than 18kW with a your lighter pack with less cells. Inadequate. Running cells at their max ratings isn't great for life. Considering what you'd spend on a pack, you probably want to consider life.
If you have specs of better cells, list them?
A123 are 3.3V, 1.1Ah and 39g. Your 19.4MJ pack is now 57kg of bare cells, though the power will be awesome. The A123s are about the best specific power, though. I would shy away from used ones, myself.
Who doesn't want their own nuclear powered aircraft? No more gas and oil, just kick the tires and light the fires!I think the only batteries that might have a chance to rival ICE in a combination of weight, endurance and power within our lifetimes are batteries that will likely not be allowed... nuclear.
No, it doesn't. To run at half power for two hours, it will need a battery that weighs over a ton and costs $100,000.However, does a 40+ lb 200 hp motor that would fit behind an RV spinner grab your attention that will be in a flight application in the near future
Certainly there is such a point, but for most applications the duration will be too small to be useful even without considering the cost and recharge time.I have been contemplating a similar calculation recently. Fuel tanks and fuel have a lower energy density than batteries - fact. But it is possible to get higher energy conversion density out of an electric motor. So where is the sweet spot? At what engine power and duration does there exist a point where the (starting) mass of the propulsion system is the same for IC as electric? (The answer might be there is no such point)