Got pulled over today

[John in CR]

...I don't see you have a link to this article about ebikes and energy efficiency? I'd really like to read it.
Ant

Ant,

I poked around and didn't find it, though I know it's linked here in the forum. I don't think Justin even boiled it down to it's simplest form, which is this:

Under optimum conditions the human body runs at about the same efficiency as an ICE, about 30% efficiency, and the average efficiency for our electric motors is over twice that. Per watt-hour of energy content food is drastically more expensive than electricity..

Bicycles are incredibly efficient machines, but that's before considering the human motor, which isn't very efficient and has very expensive fuel.

Justin's paper delves deeply into the topic and takes it out to the carbon impact too, so it's a good read.

John

[Punx0r]

Yeah, it sounds it. Hopefully I will come across on the forum.

This is getting OT, but what's got me intrigued is how a human compares to an electric motor if both run on the same fuel. Say, feed human 1lb of bread, compared to burning the bread to generate electricity and store in a battery.

I should apologise for the typo in my previous post - it should have said "I don't suppose you have a link". I didn't mean to sound rude...

[HAROX]

.

[John in CR]

Yeah, it sounds it. Hopefully I will come across on the forum.

This is getting OT, but what's got me intrigued is how a human compares to an electric motor if both run on the same fuel. Say, feed human 1lb of bread, compared to burning the bread to generate electricity and store in a battery.

I should apologise for the typo in my previous post - it should have said "I don't suppose you have a link". I didn't mean to sound rude...

It wasn't rude at all. I thought I could find it on Ebikes.ca , but didn't. Don't worry about wandering OT in any thread I start. To me they're just conversations, and if they lead somewhere interesting, all the better.

You're looking for a comparison that's going to be impossible to find, though fairly easy to figure out. In that manner they'd be close to equal and the pedal bike would come out ahead, because you're throwing in the losses of converting food to electricity.

I think a far better comparison would be to compare how much ground surface area would be required power each. 2 square meters of solar panels (maybe even just 1) is probably enough to keep an ebike supplied with electricity in typical use of say 1kwh daily (call it 700wh at the wheel). How many square meters of ground is necessary to harvest the 2000 Kcal daily that the human would need for the same output? I looked around and the most common answer was that 1 m2 of land can grow 1000 Kcal/year, so it would take about 750 m2. Even if you focused your crop on high energy food like sugar cane, you'd still be looking at about 200 m2 of land needed.

That's a pretty impressive way to look at our ebikes, a 100-300 times advantage over pedal bikes, which are pretty darn efficient. Since in the long run everything does run on solar power, this is a perfectly valid way to compare the operating costs, though it does exclude the initial investment. Plus your 2 m2 of solar panel can be raised and grow food under it, or it can be placed over an area where food can't be grown.

Thanks for sending my through that exercise. It gives us another tool for the revolution.

John

[John in CR]

That's one way to look at it, but I couldn't care less what City Hall thinks, though I do agree that we should have brake lights and turns signals as should anything out on the road including pedal bikes. If I was stateside I'd ride the same bikes I do now. I can actually build my own practical transportation, and I will not give up that freedom. If they come up with unjust laws that seek to prevent it, I will defy them as is any citizen's duty. I have no problem paying a road tax as long as it is proportionate to my use. I have no problem if a test is required to prove a certain proficiency for safe operation, or even going through a mandatory course as long as it's about real safety. I wouldn't even mind regular vehicle inspection, or a liability insurance requirement as long as it is true insurance.

In exchange for these small inconveniences that I'm willing to accept, I expect access to purchase the batteries from any factory that my tax dollars paid for or invested in. I would also expect a push to educate motorists about the rights and responsibilities of all vehicles wrt to each other if disrespect for those on 2 or 3 wheels is common in that area.

Regarding quality and durability, the junk will get run out of the market in the natural course, because there's so little cost difference in proper wiring and switches. What drive costs are speed, hill climbing, load carrying, and distance, and that's easily made reliable.

John

Not to derail "getting pulled over" but:
In the car business there's a saying. "You 'see what you can sell' or you 'sell what you can see'."
Apply that axe to someone selling a Toyota truck or a Volvo. You sell what you see, with no hype, no bullshit. Some selling that sort of vehicle can certainly say, "With proper service, you will grow to hate this (car) before it dies on you."
The powers that be in City Hall have very pragmatic senses. They are evaluating the viability of an electrified vehicle, spawned from a lowly bicycle, which moves either too slow, or too fast, or works one second and not the next, which hasn't been "taxed". The cyclists, most unlicensed and unendorsed, seem to ride as they wish, where they wish, and a good number of them don't have safety equipment, and by that I mean equipment which communicates to other drivers.
So, in few words, the Mayor sees: an erratic vehicle with no safety lights, breaking down, on the sidewalk, possibly across the City Hall lawn, driven by boobs with no conscience or safety gear.
Yeah, baby! Ask yourself, with that sort of "picture", would you, the son of a Mayor, even dare broach the subject at a council meeting? See, that's what E bike makers are up against. How do the makers change that sentiment?
1) Make things that actually do what the frock they are designed to do, and make them last longer than people expect, just like Volvos outlast our expectations (I sold my 40 year old 144E, finally)
2)Since wire is at the root of an E bike, and "wiring" is usually at the root of all the problems, make the "wiring" as good as possible. Take a clue from Apple, or Volvo.
3)Make sure what you have to sell doesn't require (lying) hyping. Just yesterday I had a salesman tell me the BB drive on his 250 watt bike could propel him at 37mph continuously, on high gear, at 86rpm cadence, on a 65# bike. Asked what size battery, he said 10Ah.
In other words, if you peddle shite, and speak shite, and cycle around on shite that breaks down more than it runs, don't expect to be anything but shite inCity Hall's eyes.
As they say in NYC, "if I can make it there, I'll make it anywhere", which leaves us all asking the question "what happens after you bullshit the biggest office in the big apple?"

[HAROX]

Agreed forver John in CR, and adding, your stuff ain't shite. ANY council would be privileged to hear your discussion, even in NYC ( though they may never have the chance ).
If we had a half dozen of you guys here... well thats off thread.
Thanks for your inspiration.

[John in CR]

Agreed forver John in CR, and adding, your stuff ain't shite. As for the topic, getting pulled over, whether you care about City Halls anywhere is not the point.
Point here is you prove to be pragmatic about your builds, and ANY council would be privileged to hear your discussion, even in NYC ( though they may never have the chance ).
If we had a half dozen of you guys here... well thats off thread.
Thanks for your inspiration.

Thanks for the kinds words. You haven't seen the stuff I don't post pics. Some are pretty fugly, and my best are still just never completed hack jobs. My point was about the cheapest of the cheap stuff. Electrics are just too easy to make reliable. Even the cheapest scooter type ebike stuff isn't all that bad once you get past the rattly plastic and cheapie switches, other than the brakes made for 20kph or less. As long as you don't put too much weight on their spindly frames they're not all that bad. My daughter loves hers. All I did was load it up with my oldest Konion packs, boosted that voltage to 20s, and beefed up the wiring for more current, as it gives her freedom of transportation...well until she bumped the back of a car not paying attention and she got her privileges revoked for a while.

Regarding laws and regulations. I accept the inevitable. That doesn't mean that I don't agree with Luke, that as long as you don't bother others in any way you should be able to do what you want. Unfortunately bad apples on both sides screw that up for everyone.

John

[Chalo]

I think a far better comparison would be to compare how much ground surface area would be required power each. 2 square meters of solar panels (maybe even just 1) is probably enough to keep an ebike supplied with electricity in typical use of say 1kwh daily (call it 700wh at the wheel). How many square meters of ground is necessary to harvest the 2000 Kcal daily that the human would need for the same output? I looked around and the most common answer was that 1 m2 of land can grow 1000 Kcal/year, so it would take about 750 m2. Even if you focused your crop on high energy food like sugar cane, you'd still be looking at about 200 m2 of land needed.

That's a pretty impressive way to look at our ebikes, a 100-300 times advantage over pedal bikes, which are pretty darn efficient. Since in the long run everything does run on solar power, this is a perfectly valid way to compare the operating costs, though it does exclude the initial investment. Plus your 2 m2 of solar panel can be raised and grow food under it, or it can be placed over an area where food can't be grown.

Your reasoning ignores the GWh that are sunk into the e-bike's copper, aluminum, lithium, nanomaterials, the photovoltaic cells, the semiconductor devices, and all the manufacturing processes thereof. It actually takes quite a long time to recoup the energy cost of PV cells, even if they are making juice to do things you can't do with pedals. That's before you get to the exotic, expensive (energy-intensive) materials and manufacturing techniques that are used in batteries.

And while exercise takes food calories, people use food calories whether they exercise or not. A transportation cyclist might exert a hundred times more muscle work than a sedentary motorist on any given day, but he doesn't eat a hundred times as much food. More like twice as much, if he's really working at it. And there are lots of costs-- energy, social, infrastructure, etc.-- of the exercise people don't get, because they were motoring instead of walking or pedaling.

Making e-bikes out to be more energy-efficient than pedal bikes is a cute parlor trick, but it's ultimately disingenuous because of all the externalities you must ignore to get there.

Chalo

[ddk]

I think a far better comparison would be to compare how much ground surface area would be required power each. 2 square meters of solar panels (maybe even just 1) is probably enough to keep an ebike supplied with electricity in typical use of say 1kwh daily (call it 700wh at the wheel). How many square meters of ground is necessary to harvest the 2000 Kcal daily that the human would need for the same output? I looked around and the most common answer was that 1 m2 of land can grow 1000 Kcal/year, so it would take about 750 m2. Even if you focused your crop on high energy food like sugar cane, you'd still be looking at about 200 m2 of land needed.

That's a pretty impressive way to look at our ebikes, a 100-300 times advantage over pedal bikes, which are pretty darn efficient. Since in the long run everything does run on solar power, this is a perfectly valid way to compare the operating costs, though it does exclude the initial investment. Plus your 2 m2 of solar panel can be raised and grow food under it, or it can be placed over an area where food can't be grown.

Your reasoning ignores the GWh that are sunk into the e-bike's copper, aluminum, lithium, nanomaterials, the photovoltaic cells, the semiconductor devices, and all the manufacturing processes thereof. It actually takes quite a long time to recoup the energy cost of PV cells, even if they are making juice to do things you can't do with pedals. That's before you get to the exotic, expensive (energy-intensive) materials and manufacturing techniques that are used in batteries.

And while exercise takes food calories, people use food calories whether they exercise or not. A transportation cyclist might exert a hundred times more muscle work than a sedentary motorist on any given day, but he doesn't eat a hundred times as much food. More like twice as much, if he's really working at it. And there are lots of costs-- energy, social, infrastructure, etc.-- of the exercise people don't get, because they were motoring instead of walking or pedaling.

Making e-bikes out to be more energy-efficient than pedal bikes is a cute parlor trick, but it's ultimately disingenuous because of all the externalities you must ignore to get there.

Chalo

you seem to ignore the thing where most people who use ebikes do so because they either can't, or won't ride a bicycle.
Get with the program!!!
I have no doubt you're right in your assertions, as you have been all along... but you seem to be missing those selling points to ebikes, which includes getting more people out of their cars/suvs et al as painlessly as possible.
-please feel free to analyze the costs of motored vehicles vs. motored vehicles whilst bemoaning the costs to society of adding a few watts of power to a bicycle. Or over the lifetime of anything that mostly pays for itself by reducing the harm caused by its' alternatives.
-Or is it you likes to play devil's advocate?. I know I do.

Actually I don't get these vs. vs. arguments.
The devices exist ...and I can purchase them. I didn't do anything else but should I have to not ensue the benefits provided by said devices just because in your opinion they took something away from something else?
Maybe I shouldn't use energy in any of it's forms
...'scuse me while I crawl back under my shell then.

[Chalo]

There's nothing bad about a 40mph e-bike in the big picture. But it isn't a bicycle, and it isn't as benign as a bicycle. Maybe I should put it in my sig file, so I don't have to keep coming back to reiterate this simple fact.

Chalo

[sn0wchyld]

I think a far better comparison would be to compare how much ground surface area would be required power each. 2 square meters of solar panels (maybe even just 1) is probably enough to keep an ebike supplied with electricity in typical use of say 1kwh daily (call it 700wh at the wheel). How many square meters of ground is necessary to harvest the 2000 Kcal daily that the human would need for the same output? I looked around and the most common answer was that 1 m2 of land can grow 1000 Kcal/year, so it would take about 750 m2. Even if you focused your crop on high energy food like sugar cane, you'd still be looking at about 200 m2 of land needed.

That's a pretty impressive way to look at our ebikes, a 100-300 times advantage over pedal bikes, which are pretty darn efficient. Since in the long run everything does run on solar power, this is a perfectly valid way to compare the operating costs, though it does exclude the initial investment. Plus your 2 m2 of solar panel can be raised and grow food under it, or it can be placed over an area where food can't be grown.

Your reasoning ignores the GWh that are sunk into the e-bike's copper, aluminum, lithium, nanomaterials, the photovoltaic cells, the semiconductor devices, and all the manufacturing processes thereof. It actually takes quite a long time to recoup the energy cost of PV cells, even if they are making juice to do things you can't do with pedals. That's before you get to the exotic, expensive (energy-intensive) materials and manufacturing techniques that are used in batteries.

And while exercise takes food calories, people use food calories whether they exercise or not. A transportation cyclist might exert a hundred times more muscle work than a sedentary motorist on any given day, but he doesn't eat a hundred times as much food. More like twice as much, if he's really working at it. And there are lots of costs-- energy, social, infrastructure, etc.-- of the exercise people don't get, because they were motoring instead of walking or pedaling.

Making e-bikes out to be more energy-efficient than pedal bikes is a cute parlor trick, but it's ultimately disingenuous because of all the externalities you must ignore to get there.

Chalo

and you also ignore the energy required to cultivate, maintain, protect and harvest your food, and then process it into somehting edible? and then store it for times when your 750sqm or whatever it is cannot produce food ie winter? and transportation for that food since there's no practical way to have 750sqm of land per person in cities etc? and the energy required to cook the food? and practically, do you really think people will survive well on 1 food type? - ie you'd probably have to be a vegitarian, since I doubt you could raise many animals on that size of land... which brings up some other health issues... and compare all this over the 3-10 year replacement life cycle of the ebike's electronic components?

Im not in total disagreement with your point, but if you're going to compare the full systems energy usage, you need to do it on both sides, otherwise its nothing more than a cute parlor trick...

[mark5]

There's nothing bad about a 40mph e-bike in the big picture. But it isn't a bicycle, and it isn't as benign as a bicycle. Maybe I should put it in my sig file, so I don't have to keep coming back to reiterate this simple fact.

Benign--like this bicycle

Cyclist accused of vehicular manslaughter over pedestrian's death pleads not guilty
http://usnews.msnbc.msn.com/_news/2012/06/21/12330744-cyclist-accused-of-vehicular-manslaughter-over-pedestrians-death-pleads-not-guilty

[Sunder]

There's nothing bad about a 40mph e-bike in the big picture. But it isn't a bicycle, and it isn't as benign as a bicycle. Maybe I should put it in my sig file, so I don't have to keep coming back to reiterate this simple fact.

Benign--like this bicycle

Cyclist accused of vehicular manslaughter over pedestrian's death pleads not guilty
http://usnews.msnbc.msn.com/_news/2012/06/21/12330744-cyclist-accused-of-vehicular-manslaughter-over-pedestrians-death-pleads-not-guilty

If that's what a bicycle can do, imagine what it would be like adding another 15-20kg of weight to it, another 30km/h and the potential for poorly engineered sharp edges and other hard items - not to mention that we're carrying a fair bit of flammables and high voltages on some our bikes.

He did say "isn't as benign", not that a bicycle is totally benign.

[Joseph C.]

Benign--like this bicycle

Cyclist accused of vehicular manslaughter over pedestrian's death pleads not guilty
http://usnews.msnbc.msn.com/_news/2012/06/21/12330744-cyclist-accused-of-vehicular-manslaughter-over-pedestrians-death-pleads-not-guilty

Psychopathic scum.

[Sunder]

One other comment I thought would be good to make.

Australia and America has an obesity epidemic. Without researching too much, I believe the weight of an average American is about 20 pounds above the ideal weight. That's not to say everyone is. Some people might be 100 pounds overweight, while others are underweight.

There is 3500 calories or so in a pound of fat.

According to Google, "1 calorie = 1.16222222 × 10-6 kilowatt hours". However, a food calorie is actually a 1000 scientific calories.

So it's more like 1.162 x 10^-3, or roughly 860,000 calories to the kilowatt hour, or roughly 860 food calories to the kilowatt hour. Someone else can provide the figures for me, but I believe at a reasonable rate of riding, you could get about 60km out of a 1kwh? If so that's 49,000km you could do, based solely on the fat stored in overweight people - or roughly 2 years worth of driving in an average car.

So just from the average fat alone, we could save 814kw hours!

The answer is clear. Fatties, get on yer bike and contribute some of that energy back to the world instead of storing it! Once you're in the healthy range, then you can start charging up from the wall, or eating more, which ever is your preference!

{/end tongue in cheek post]

[veloman]

With this discussion over energy efficiency between bicycles and ebikes, it comes down to this IMO:

The average person should exercise daily or most days per week. The recommended amount is 30 minutes or something like that. That fits in pretty well for city dwellers who only need to go a few miles across town and back. Bicycling can be a great commuting option, for getting in that exercise, but only if other variables add up to support that mode. Such as: safe infrastructure to allow going 12-15mph or so. Also, a lifestyle that may allow you to sweat in the summer without having to take a shower at your destination. Or maybe there is a shower there and it fits in okay to use it.

So I think if you meet the above reasonable requirements, enjoy pedaling, and don't travel much more than 6 miles a day, then bicycling can work out well and would be more energy efficient.

But welcome to the real world, where we have extreme lacking cycling infrastructure (and really, doubling your speed to 25-30mph is all you need in most cities to stay much safer, longer commutes, hot weather (definitely where I live), hills, and the desire to not always have to labor yourself to get somewhere. Of course there are die-hard commuter cyclists ( I was one) who would ride mega distances each day, but we are talking average humans here.

Bottom line is that the first 5 or 6 flat miles each day "should" be exercise, if possible. But the better option IMO is to have a ~1200watt 'economy/simple' ebike (basic reliable, affordable, plug n play last a long time lifepo4). You pedal when it makes sense, helping the motor so you achieve decent performance/range, without needing the extras of a high power, longer range setup. Maybe it really doesn't matter if you ride a 5kw ebike, but then cost DOES go up a fair bit, especially for a turn key battery (remember, we are talking average person, not you lipo hobbyists). No other mode of transportation has the ability to move as efficiently, quickly, with as little impact, with as much freedom and affordability as the above ebiker, all the while still offering the opportunity for rider exercise that has a meaningful contribution to performance.

Go ahead and tell me that pedaling through traffic wave pollution is better than holding my breath and throttling out of it quickly. I get to the quiet roads and hit the pedals hard for some spirited acceleration and exercise. You have the option on an ebike.

And really, the efficiency discussion is practically mute because the amount of energy we are talking about is so minute compared to how much power is wasted in western civilized society. What is the point in arguing it? Pick the mode that fits you best, not because it's a sliver better the other. It's like a pedal cyclist is an impact number 30 and ebiker is 40, while a car is 1500 and running the AC 1 degree cooler in your house is an 800.

[Sunder]

And really, the efficiency discussion is practically mute because the amount of energy we are talking about is so minute compared to how much power is wasted in western civilized society. What is the point in arguing it? Pick the mode that fits you best, not because it's a sliver better the other. It's like a pedal cyclist is an impact number 30 and ebiker is 40, while a car is 1500 and running the AC 1 degree cooler in your house is an 800.

+1

[Lessss]

Top gear of my stealth bike is faster than my hub motor(yes it's a legal 32Kph top motor), I find I don't have to shift down at stops, I just use the hub to get back up to speed then engage pedaling.

[Cresh]

But welcome to the real world...

+1 well said!!!

2003 giant Yukon, Mac 7t, 52v

[John in CR]

Transportation is a different subject from exercise, and for the tiny minority that can combine them great, but it's irrelevant to the discussion unless pedelecs only are mandated, in which case popularity will suffer drastically. Food as fuel for transportation is a breakeven proposition at best, and that's special purpose crops only for ethanol as fuel for ICE's, not consumption. For food it's 2-3 fold higher in land requirements and other costs to produce it.

90% of my battery stockpile is recycled batteries, so that's a plus not a negative.

My 50mph ebike, 55mph ebike, 59mph super ebike, and 60mph cargo ebike all have 2 wheels and are not legally any type of motor vehicle. Since they have 2 wheels, whether anyone likes it or not, they are bicycles, so get over it. Sure they blur the line between what are commonly motorcycles and bicycles, but they have enough bicycle gene for the locals to call them bicis not motos, and they're legally bicycles, so to insist that they're motorcycles is trolling. Just like Sam Whittingham's velo didn't turn into a motorcycle just because he pedaled in up to 82mph, if someone took an identical velo and installed a small electric motor to propel it to the same speed it would also stay just a bicycle.

I'm secure enough that I really don't care what anyone calls my ebikes. I'll cross the bridge of legality once there is one, and hopefully I can direct input toward open minds during it's construction so ebike growth here isn't stifled by rules. What's upsetting though is ESers who get hung up on rules, not about how they affect themselves which is understandable, but in how the rules need to be enforced on others, and even worse to be in favor of new rules that specifically further restrict or attempt to exclude fellow ebikers...some even based soley on what they look like. How can any member disagree with the simple concept of "the more ebikes the better"? It's an easy concept to embrace. Just imagine how much better the world would be if tomorrow everyone who has a distance to travel that is practical for an ebike, rode one.

To me there shouldn't be any hesitation about embracing that concept. It comes with compromises, so it won't be everyone holding hands and singing Kumbaya. It's going to take time to grow more infrastructure, and that means what exists is going to be more crowded, and with clueless noob riders on ebikes some of us wouldn't be caught dead riding. Let go of all your preconceived notions and share the way and be friendly and helpful by welcoming them to the future, and by letting them know the proper etiquette if they appear ignorant about how things work. If they look like an accident just waiting to happen give them some riding or safety tips. Accept the fact that if their ebikes have performance limited to that of pedal bikes, then they belong right there too.

There's another important facet to being a real ebike ambassador. It's a simple fact that many, if not most, will want more power than what is legally permitted. These high power ebikes will be available as "off road" versions, and people will build a lot more of them too. Not only will people ride them on the road, but they'll ride them on the paths. As long as they aren't being a menace by riding in a manner that shouldn't be accepted for pedalists either, then why should you care whether they have a license plate? Just let them ride in peace and stop calling their ebikes electric motorcycles. All you're supposed to care about is being happy that they're on an ebike and not in a car. Also, keep in mind that in many jurisdictions it's impossible or at a minimum extremely difficult to get these kinds of ebikes registered, but that doesn't mean they shouldn't exist or that they shouldn't be used as basic transportation, as long as they aren't causing any harm to anyone else. Whatever legal risk they have is their business, not yours.

IOW do anything you can to promote the use of ebikes, and that includes not discouraging anyone who rides one as long as they ride in a responsible and respectful manner.

John

[remf]

Interesting discussion. Sure pure cycling is very efficient for 5 mile rides or so. Beyond that, the extra calorific intake required makes that statement somewhat dubious. Take into account the intensive agriculture, processing, packaging, food miles and local transport and you begin to get a more realistic perspective...unless you're a subsistence farmer. And that's for every day you ride those 30 mile rides on your unpowered road bike. The 'hidden' costs of electric bike manufacture referred to by Challo are one off, at least for the lifetime of the battery, motor & other components.

Here's a great paper on the subject by Jeff Radke...the conclusion is clear - "The electric bicycle is the most cost effective means available to address global warming through CO2 emission reduction."

http://neodymics.wordpress.com/article/ ... kub8bcr-6/

[The Mighty Volt]

Great discussion. I did used to think a lot about how many calories I needed to take in to keep my road-cycling going at an efficient rate. I "solved" the problem by eating less-processed foods, such as potatoes, and by cycling hard up-hill and doing nothing down-hill, and barely turning-over on the flats.

[Punx0r]

Just for comparison, 100g of milk chocolate contains about 500 food calories. So 860 calories would be about 170g of chocolate.

Lipo at 150Wh/keg would weigh ~6.7kg to store the same amount of energy.

[John in CR]

Just for comparison, 100g of milk chocolate contains about 500 food calories. So 860 calories would be about 170g of chocolate.

Lipo at 150Wh/keg would weigh ~6.7kg to store the same amount of energy.

Please, by that logic even assuming the batteries only lasted a year that would be 62kg of chocolate. Plus you forgot about efficiency, so multiply it by 3-4, and 200kg is a decent estimate.

[Punx0r]

I wasn't trying to make a point, just thinking out loud about energy density.

In terms of fuel weight for a single journey, even if a human is an inefficient engine (quick google search suggests around 25%?) that's still only ~700gm of fuel per Kwh of work.

Our 6.7kg of lipo needs derating by 20% for it's own longevity and then by probably another 20% to account for battery/controller/motor inefficiency.