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A question/query for those of you with more knowledge about batteries, charging etc.
While thinking about bikepacking in a bivvy type environment, there is obviously a long standing, though unanswered question about what happens if you begin to run out of power long before you reach your destination.
Is there an option to put back some of the charge by other means, given in the middle of nowhere you cant recharge, so was wondering about a hand crank generator and would such a thing be capable of putting back some or enough power, to get you back to the hotel/b&b/trainstation, but i know nothing about electrics as ive never researched the subject, so though to ask here with its deep collective knowledge.
Someone on another thread suggested having a dynamo on an ebike, to put or return some of the power that you use, like on a car, which is a very good idea especially as theres no charging points 50 miles in the middle of the Highlands. I wasn't sure a simple dynamo would supply enough charge, but again ive not researched the subject, but acknowledge its a good idea and maybe one that should be explored.
There are many options of hand powered generators and they have i believe been used by the military for decades(remember seeing one in an old B&W ww2 movie, but would have though such a good idea would hang around and likely someones improved on it, or such.
So any sparky's out there want to take such a question on ?.
I have used one in a two way radio system ( army surplus). Ok a good few years ago when electric tech was not so good but it was an hour cranking to get 5 mins of radio
As for the dynamo on an ebike - its orders of magnitude too low powered to put anything back into the ebike battery.
Eidt - i am struggling with the calculation but 1000 hours of bicycle dynamo flat out to recharge the ebike battery? Half a watt output into a 500 w hr battery?
If you do some back of the envelope calculations, you're not going to get far with a hand cranked generator.
From this link, USB power banks for recharging phones and laptops are typically 20 to 50 mAh.
https://www.techradar.com/news/top-portable-chargers
20 mAh at 5v is 100Wh. A moderately fit cyclist can sustain 200 W for an extended period, but getting over 300 W requires being fairly fit. The generator and charging won't be 100% efficient, so you would be looking at a moderately fit cyclist pedaling for an hour or so to charge a powerbank that can charge several smartphones.
Your legs are much stronger than your arms, so you would be spending hours cranking away on a hand cranked generator to charge up even a small powerbank.
It would be much better IMO to make a generator to replace the back wheel, with a folding stand to support the bike. Then, at the end of your hours of cycling, you get to ride an exercise bike for a couple of hours so you can watch Netflix. It might be worth it if you were cycling across Africa or Siberia, but it just wouldn't be worth it for most bikepackers. Much easier to just buy an extra powerbank and not use electrics so much.
Great answers so far, indeed its a difficult situation technology wise. But I do think there needs to be a solution, at lease for ebikes in order to modify what you have to recharge the system, even if it only gives you 50% charge.
Maybe some way of using the bike itself, propped up on a stand and in the evening you pedal away to recharge some of what youve lost.
Maybe its still decades down the line 😕
Great answers so far, indeed its a difficult situation technology wise. But I do think there needs to be a solution, at lease for ebikes in order to modify what you have to recharge the system, even if it only gives you 50% charge.
Maybe some way of using the bike itself, propped up on a stand and in the evening you pedal away to recharge some of what youve lost.
Surely at this point you just ride *not* an ebike.....
Physics dictates that you will be expending the energy one way or another.
Maybe some way of using the bike itself, propped up on a stand and in the evening you pedal away to recharge some of what youve lost.
would take hours and need a complete redesign with great complexity to the drive train - you have 3 freewheels in a bb mount motor system - all would need to be capable of reversing to make this work so would need to be either manual or magnetic clutches rather than freewheels and yo still run up against physics in that several hours of flat out riding would be needed to put charge into the battery.
Someone on another thread suggested having a dynamo on an ebike, to put or return some of the power that you use, like on a car, which is a very good idea
And I think it was pointed out that this person had solved all the worlds energy problems by inventing perpetual motion.
If you've got sufficient physical capacity to charge a large battery with your arms, leave the stupid e-bike at home and pedal your meat bike properly.
And I think it was pointed out that this person had solved all the worlds energy problems by inventing perpetual motion.
Good point. It's Dyna ti's monthly troll on the matter. It was windturbines last month
<perchypanther> I think the OP is ‘winding us up’ with these illogical questions! </perchypanther>
I've this thing called a paper Map. It never needs charging.
Other electronics are then just superfluous, no?
Otherwise op you're suggesting technology to look after technology, to look after technology, so that we can use technology later.
But I do think there needs to be a solution, at lease for ebikes in order to modify what you have to recharge the system, even if it only gives you 50% charge.
If you're doing multi-day rides without any charging along the way, just ride a normal bike. Or, turn the assistance right down and use it only for the worst climbs, for example, limit it to 5 km/h, if that's possible. Then carry enough spare batteries to get you between charging points. Trying to charge an e-bike with a human powered generator will never be viable because of the basic physics involved.
[matrix] "who's really in control"
"Humans we can turn off the machines any time we want"
" Yes but then we have no air and no water"
"So we need the machines to stay alive and the machines need us to stay alive"
[/Matrix]
20 mAh at 5v is 100Wh. A moderately fit cyclist can sustain 200 W for an extended period, but getting over 300 W requires being fairly fit. The generator and charging won’t be 100% efficient, so you would be looking at a moderately fit cyclist pedaling for an hour or so to charge a powerbank that can charge several smartphones.
Fixed your maffs for you:
A a modern phone battery is 4Ah at 3.8V.
4 * 3.8V * 3,600 is ~55,000J. So if you could extract all the energy from the cranks riding at 200W you could charge your powerbank in 275 seconds. Assuming you're willing to sacrifice 10% of your energy to a dynamo, and that dynamo is 50% efficient, this lets you charge your phone at 10W.
Your phone will be recharged in 90 minutes.
I'd look at one of the folding solar panels. Alternatively many of the newer Chinese phones have huge batteries and ultra-fast charging so if you can convince a cafe owner to let you plug it in then it will refill over a coffee. You can also get gas stoves that have a tiny peltier inside to generate electricity.
Fixed your maffs for you:
No, you replaced it with something different. Those powerbanks are nominally 5 V. 4 Ah at 3.8 V is 15.2 Watts for one hour. Charging will not be 100% efficient, so a cyclist who can sustain 200 W will probably only be able to produce 100 W of continuous power (these are ballpark figures). Your phone battery is roughly one sixth the capacity of a small powerbank, so it will only take one sixth the time to charge.
You can also get gas stoves that have a tiny peltier inside to generate electricity.
What will recharge the gas though.
You lot have all got the wrong end of the stick, he's talking about recharging an e-bike battery, not a phone!
Easy to see how from the original question, granted. Clarity of the post is about the same standard as his grasp of basic physics.
What will recharge the gas though.
Jerusalem Artichokes
ive patented a new gas-battery for exactly this scenario - it looks a lot like a hydration bladder mounted upside down so the valve comes out of the pack at the bottom (and also at the bottom)
You lot have all got the wrong end of the stick, he’s talking about recharging an e-bike battery, not a phone!
That was obvious from his later post, but the general point is that even a fairly small powerbank will take hours of hand cranking to charge. Charging an e-bike battery from human power makes no sense at all - you'll always spend more time charging it than you will save from riding faster.
@ Rat and fish.
Just having people think about whats possible. Drives human invention don't you know. Not everyone is living in the dark ages, but if posting such is a troll then I'll refer to you in future before doing so. Thanks for the time, sorry to have troubled you guv... but if it's any consolation, I didn't understand those electrical formulas either.
(Was it not solar panels before wind turbines, or am I mixing it up 😕 )
stupid e-bike at home and pedal your meat bike properly.
Sounds like you have electrical issues yourself 😉
I love cycling my 'meat' bike, properly and otherwise, but I fear my concerns that bike packing might for me be a thing of the past if the worry of running out of power into the trip prevents me from even attempting such radical behaviours in the first place.
Telephones without wires ?, Humbug 😕
What's the point in riding an ebike in max assist for 5 hours to get to your campsite, only to then spend another 5 hours on a static bike in 'regen mode' pedaling away like a lunatic to recharge the bike battery? Just turn the assistance right down so that you use less charge. You'll expend less energy overall because you won't have the losses from recharging.
Clarity of the post is about the same standard as his grasp of basic physics.
I was terrible at physics, chemistry was more my line.
Especially in the 1990's
Those with electric cars tell me range anxiety goes away with use.
Maybe you could try hydro power in a stream
Towing a small petrol generator to your area of beauty and tranquility
A second battery (the only serious realistic answer I've written here that won't require the laws of physics to be rewritten to allow you to bike pack.)
chemistry was more my line.
Especially in the 1990’s
Indeed alot of abuse of 90s chemicals leads to grey matter shortage in old age.
How do you recover the energy expended trolling though?
On a serious note, surely regenerative braking would be great on an e-mtb. It could bimble you to the top, then reclaim most of that energy as they mince down the trail dragging the brakes?
You probably could get enough energy from a small hydro machine that was light enough to carry.
Just having people think about whats possible. Drives human invention don’t you know.
It's not possible to change energy from one form to another without losing some. That's a basic principle of physics.
If you use human power to charge a battery, then use that battery to power an electric motor to drive the back wheel, you will end up with less energy at the back wheel than if you just used the human to drive the back wheel directly. Therefore, setting the bike up like an exercise bike in the evenings to charge the battery will leave you more tired than if you just rode a normal bike. If you want to go bikepacking with an e-bike, you will always be limited to routes where recharging is available.
In principle, it would be possible to use regenerative braking, where the motor is switched to being a generator when you apply the brakes. However, that would require the entire drivetrain to be redesigned in quite a fundamental way compared to the standard e-bike system, which uses a freewheel at the back wheel and the motor mounted in the frame.
On top of that, you would only be able to recover a small fraction of the original battery power because it would only recharge when you are dragging the rear brake. Any braking done on the front brake would be wasting energy, so you would need to train riders to maximize the energy recovery by riding fairly slowly on descents and just dragging the rear brake the whole way. That's going to be fairly dull for most people. As soon as you go fast enough to have fun, you will either lose energy through aero drag and/or need to use your front brake to set up for corners. This just will not be worth the cost and complexity on an e-bike. Cars are a different thing, they are vastly more powerful so regenerative braking is worth implementing for them.
I used to work on these
Energy hand bike
To sustain 100W (Max for this design) for several minutes was hard work. the newer design with contactless generator was better. A smaller crank radius that I would envisage a portable device would have would make it even harder.
How do you recover the energy expended trolling though?
Sorry, is that directed at me, who merely posted a question, or trailrat or tjagain, who seem very keen with their multiple derogatory answers.
These old brain cells you know, in fact another year older today, they just cant keep up.
so you would need to train riders to maximize the energy recovery by riding fairly slowly on descents and just dragging the rear brake the whole way. That’s going to be fairly dull for most people.
I refer the honourable gentleman to the "Sauron at Swinley" thread.
In essence though, it doesn't need to be all that efficient. Seeing as you have your legs to top it up.
After all e-bikers are always telling us they pedal just as hard as the rest of us ( 😁😂🤣 ), so if they're climbing at ~250W for 20 minutes on a middling boost setting (~75W) you only then need a battery that can hold that 75W for one climb. About 50Wh rather than 500Wh. so you only need to recover about a fifth of the energy.
The real issue is as you mentioned, how do you build a 1kw+ dynamo front hub to make the most of the regenerating, and make it lighter than the big battery.
Christini is still going, and they're now making e-bikes as well..... where there's madness, there's a method!
