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Old 04-01-07, 09:58 PM   #1
WishYouWasMe
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E-Bikes Recharge

Why isnt there a technology like Toyota uses for its hybrids where the power you put into the system keeps the battery charged?
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Old 04-01-07, 10:05 PM   #2
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Some companies use regenerative braking (EV Tech for one), but mostly it's a dance around the second law of thermodynamics. You have to put more power into a system than you can get out of it, and adding systems to charge the battery on the fly add weight and complication for little return. For instance I have a generator hub on my Giant Lite (runs the lights); if I were to use it to charge the battery, I would have to pedal over 400 miles, without using the motor, to fully charge the battery, which is good for 30 miles.

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Old 04-01-07, 10:05 PM   #3
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Some kits do have regnerative braking - IE the Bionx. You don't see it on too many other kits since it doesn't help nearly as much on a far lighter vehicle as a bike.
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Old 04-01-07, 10:06 PM   #4
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You do get back energy if you utilize the regenerative recharging for when you would typically be braking... just not 100% of it.
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Old 04-01-07, 10:19 PM   #5
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Originally Posted by AllenG
Some companies use regenerative braking (EV Tech for one), but mostly it's a dance around the second law of thermodynamics. You have to put more power into a system than you can get out of it, and adding systems to charge the battery on the fly add weight and complication for little return. For instance I have a generator hub on my Giant Lite (runs the lights); if I were to use it to charge the battery, I would have to pedal over 400 miles, without using the motor, to fully charge the battery, which is good for 30 miles.
Well then maybe electric power isnt the best for a bike. Maybe hydraulics-assisted bikes would be better...or hydro-assisted bikes. For instance....change the shape of a chain on a bike and you can change the direction the force can come from to could be used to propel it. Maybe if you could create a hybrid chain system...you could use compressed air for assistance or maybe even water for extra power. Im just thinking...but compressed air would be extremely easy to power a bike since it can easily be replaced with a hand pump.
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Old 04-01-07, 10:31 PM   #6
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Energy per volume or weight (there is a term I'm looking for that I can't remember, the engineers will know). Compressed air takes up a lot of room, and to have any range the storage tank is going to be quite large, and therefore heavy. Water powered systems use pressure, same as compressed air, since fluids cannot be compressed they have to use gravity (your bike would be many stories tall) or contained in a closed loop. There the pressure would be added by compressed air, and you would have to have tanks again.
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Old 04-01-07, 10:42 PM   #7
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Originally Posted by AllenG
Energy per volume or weight (there is a term I'm looking for that I can't remember, the engineers will know). Compressed air takes up a lot of room, and to have any range the storage tank is going to be quite large, and therefore heavy. Water powered systems use pressure, same as compressed air, since fluids cannot be compressed they have to use gravity (your bike would be many stories tall) or contained in a closed loop. There the pressure would be added by compressed air, and you would have to have tanks again.
unless you could build a circulatory system for it. I dont know how any of this would be done im just brainstorming lol so I know most of it probably isnt feasible. In some fashion though...the compressed air might possible be created on spot by a mechanism that creates a vaccum similiar to a turbine. A small turbine powered bike should work in this fashion. My thing is that there has to be some way to multiply the wattage generated by these interactions.
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Old 04-01-07, 10:49 PM   #8
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What powers the turbine?
People have been trying to improve on the bicycle for quite some time and it's hard to beat the basic old bike. A human on a bike is one of the most efficient forms of movement to be found.
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Old 04-01-07, 11:16 PM   #9
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Originally Posted by WishYouWasMe
unless you could build a circulatory system for it. I dont know how any of this would be done im just brainstorming lol so I know most of it probably isnt feasible. In some fashion though...the compressed air might possible be created on spot by a mechanism that creates a vaccum similiar to a turbine. A small turbine powered bike should work in this fashion. My thing is that there has to be some way to multiply the wattage generated by these interactions.
First Law of Thermodynamics: You can not get more out of a system then you put in to it.

Gasoline has a very high "Energy density" making for a lot of mileage/speed for a relatively small volume. Sorry about that Chief. Compressed air is very inefficient. I have seen the video of a German who mounted a honest to God jet turbine on a bicycle. Funny once.
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Old 04-01-07, 11:30 PM   #10
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Originally Posted by ken cummings
First Law of Thermodynamics: You can not get more out of a system then you put in to it.

Gasoline has a very high "Energy density" making for a lot of mileage/speed for a relatively small volume. Sorry about that Chief. Compressed air is very inefficient. I have seen the video of a German who mounted a honest to God jet turbine on a bicycle. Funny once.
did it work?
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Old 04-02-07, 06:06 AM   #11
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The best energy storage and release system for bikes is called "a hill".
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Old 04-02-07, 09:00 AM   #12
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Turning an electric motor into a generator for regenerative braking is an excessively complicated thing to do. If using a commuter and brushes you need two sets of them and a relay to switch between them. They also end up very narrow as the separation is very close. If you attempt to use the same set of brushes for motor and generator operation they will burn out very quickly leading to services intervals and high service costs which most people will not put up for. It would be terrible telling the consumer he/she must bring in there bike every 6 months or so for new brushes in there motor. Brush-less hubs are another option but you need double the number of coils in the motor, one set to function as a motor and a second set for regenerative braking which also leads to complication, added weight, and brush-less systems are less efficient than brushed systems. Add to the fact that regenerative braking simply will not contribute enough returned energy to make a truly notable extension of range. As a matter of fact the additional weight penalty incurred for regenerative braking would cause more energy to be used from the battery than regenerative braking could replace so you could actually lose range with regenerative braking as compared to a simple and cheap brushed motor system.
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Old 04-02-07, 09:34 AM   #13
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Originally Posted by ken cummings
First Law of Thermodynamics: You can not get more out of a system then you put in to it.
First law, not the second, that's right, I haven't had to pay attention to them in years.
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Old 04-03-07, 09:14 PM   #14
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The best energy storage and release system for bikes is called "a hill".
Thank God for potential and kinetic energy *sigh* (at all this techno talk)
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Old 04-04-07, 02:17 AM   #15
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...

Last edited by Horse; 04-18-07 at 10:14 AM.
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Old 04-04-07, 03:32 AM   #16
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. . .These things are plug-in hybrids.
Yeah, but ebikes make financial sense not to mention they are an entire order of magnitude more energy efficient at getting a person from A to B.

<OPINION ALERT>

Regenerative braking is worthless for anything other than reducing brakepad wear. The weight/complexity would better be spent on a foldup PV charger that could be rolled out on the ground to top off the battery while the bike set idle.
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Old 04-04-07, 06:53 AM   #17
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Weight and complexity? A motor and generator are essentially one the same... as are headphones an microphones. With an additional circuit board and perhaps I believe some kind of converter/inverter, there is hardly any more weight. The Bionx PL-350 w/ regnerative braking is one of the lightest systems around!
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Old 04-04-07, 02:13 PM   #18
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Originally Posted by priu
Weight and complexity? A motor and generator are essentially one the same... as are headphones an microphones. With an additional circuit board and perhaps I believe some kind of converter/inverter, there is hardly any more weight. The Bionx PL-350 w/ regnerative braking is one of the lightest systems around!
Do you own a Bionx? Have you done any informal range testing?
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Old 04-04-07, 07:07 PM   #19
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My old Zap motor can be recharged by pedaling. But it's so hard to do you can't ride a 1/4 mile without getting too tired. The amount of current used to recharge a battery in any reasonable amount of time is too much to subtract from your pedaling effort.

Electric bikes are not as nice as a good pedal bike anyway. Unless you are not healthy, then they are useful if you stay very close to home.
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Old 04-04-07, 07:32 PM   #20
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. . .Electric bikes are not as nice as a good pedal bike anyway. Unless you are not healthy, then they are useful if you stay very close to home.
If I can assume you are basing the above assertion on your Zap kit then I can understand why you might think that.
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Old 04-04-07, 10:04 PM   #21
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While I don't have a bionx kit myself, I have a Ford Th!nk electric bike (non-regenerative braking)... and am putting together a radical kit for my Sun EZ-1 SX recumbent. That being said, I did TONS of research into kits for my recumbent - and Bionx was one of my main choices. Bionx - especially for the kind of hybrid pedelec performance w/ the 350W - is one of the best I've seen in terms of performance vs weight.

By radical - I mean that it's going to rip - theoretically it will hit 45 mph... no regenerative braking on mine - and it would be quite useful for me... but I'll take the power of the 37V ecospeed kit I'm building vs a hybrid setup meant to make you go faster and farther a la the Bionx.

But if you look up pictures of the Bionx parts - you'll see that the regen adds no weight... a slightly more complex circuit - but I wouldn't call that as adding complexity .

Last edited by priu; 04-04-07 at 10:26 PM.
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Old 04-04-07, 10:37 PM   #22
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While I don't have a bionx kit myself, I have a Ford Th!nk eletric bike (non-regenerative braking)... and am putting together a radical kit for my Sun EZ-1 SX recumbent. That being said, I did TONS of research into kits for my recumbent - and Bionx was one of my main choices. Bionx - especially for the kind of hybrid pedelec performance w/ the 350W - is one of the best I've seen in terms of performance vs weight.

By radical - I mean that it's going to rip - theoretically it will hit 45 mph... no regenerative braking on mine - and it would be quite useful for me... but I'll take the power of the 37V ecospeed kit I'm building vs a hybrid setup meant to make you go faster and farther a la the Bionx.

But if you look up pictures of the Bionx parts - you'll see that the regen adds no weight... a slightly more complex circuit - but I wouldn't call that as adding "complexity."
I don't want to write anything ill of Bionx, but it's kind of funny that my simple, gearless hubmotor equiped roadbike easily gets 2X-3X the range of the Bionx owners that I know while running on "inferior" lead acid batteries and no regenerative braking.

Sounds like you've got an interesting project on your hands; 45MPH is just a little too capable for my needs. For that kinda speed, I would seriously consider retrofiting that CLWB recumbent with disk brakes if you can even find a "16" steel fork with disk brake tabs. 20" disk brake forks are readily available maybe you could find a used Tour Easy for your project.
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Old 04-05-07, 04:24 AM   #23
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Originally Posted by AllenG
What powers the turbine?
People have been trying to improve on the bicycle for quite some time and it's hard to beat the basic old bike. A human on a bike is one of the most efficient forms of movement to be found.
That's right.

Can't get away from the math. Both sides of the equation input-weight=force
Change one you gotta change the other..add an electric motor..cool but that adds weight/battery's/resistance "not cool".

I was originally looking for a ebike for my commute but by the time i'd factored in the cost/charge time/weight it was starting to look like i would be better off with a ICE machine (i.e. motorcycle) which means 'no' health benefits for me...so until someone can figure out a fusion engine or fully solar cycle i gotta stick with my human powered bike...Actually even if I could get a nuclear powered bike i'd still be cheating myself out of the health benefits... Wish someone could figure out a way to make them fly.. That'd be cool...just a few feet off the ground would be fine by me...

Cheers..
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Old 04-05-07, 07:13 AM   #24
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Regen has its uses. It would add a bit of complexity and a teenie bit of weight if you or I were to tack on regenerative braking onto our bikes - I think we'd have to get an inverter and different controller or something - I'm not too familiar with the details. With the Bionx, it's integrated into the circuitry - meaning no additional weight or complexity for that setup.

Here's the thing about regen... you don't use your energy to charge the battery - that's not the most efficient use of energy (as has been said by yourself and others)- but one should use it whenever you would've been wasting energy by burning off the energy as heat. Bionx is pushing the percentage of electricity you can get out of it - there's hardly any potential/kinetic energy vs something like a hybrid car (I have a Toyota Prius).

I think one of the Bionx options includes the ability to use regen when you hit the brakes lightly - just like a hybrid car... and that makes for proper usage of the regen system.

If you live in flat areas - you're only going to see about a mild boost to total battery power... with a larger boost in hillier areas.......I'd venture to say 'moderate'.... now keep in mind I am speaking with a reference point of a non-electric bicycle.

---------

I appreciate the advice - the Tour Easy is out of my budget for now - but I will look into 20" forks w/ disc brake tabs. The previous owner (bought the recumbent used) put in 20" forks - but they use standard brakes. Thanks!

Which hub motor are you using? A crystalite? Weizmann (sp?)?
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Old 04-05-07, 10:44 AM   #25
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i have a bionx and the best part about it is that it helps you slow down without using your brakepads. It's really great for controlling your speed on a long descent or in the rain. And, of course, you can capture some of that energy when braking since it's integrated with your brake system.

However, I think the cogging effect (the electromagnetic drag) present in these kind of motors and needed to make regen possible is great enough that you're better off without regen in terms of total efficiency. The cogging effect slows down my descent even when regen is not enabled. On the same downhill, I can probably hit 35mph on a regular bike, but on the bionx bike, i hit about 28mph. But this effect is mainly felt when going over 20mph.

Overall, having an electric assist is the best thing you can add to your commuting bike. I could go on and on about the benefits of ebikes. But I'll just say one thing. Because you're going faster and accelerating faster, you'll have a tendency to use the roads more like a car (which you should be doing anyway), making your commute safer in the end.
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