E-bike battery charging while riding

[LI-ghtcycle]

Hello, I have searched the board and found several similar posts, but none that matched my question.

How easy would it be to have a special controller that would turn your powered E-Bike's motor into a generator for the batteries? I ask because I often ride around un-powered with my E-Bike, and if I wanted to extend my range, it wouldn't be that much, but even if I could get 10% that would be great. I know there are regenerative breaking equipped controllers, but I haven't heard of anything that would turn the motor into full generator mode.

I realize that this would cause a good deal of friction and would require me to sweat, but that's ok with me, if I could simply gear down to deal with the extra load, in order to extend my range, that might be worth it to me on a long trip.

Thoughts?

Thanks!

 

[monster]

why don't you just ride a push-bike then?

 

[LI-ghtcycle]

Because I like the power going up hills, and because I have Fibromyalgia, I can't always ride a push bike un-assisted.

 

[dogman dan]

The infineon controllers at Ebikes-ca may be your easiest solution, the web page says they can program them for regen. But the battery has to be of a type that can take the return current. Many of the lifepo4 kind can't take reverse current to the bms. I'd talk to the folks at ebikes-ca about it and tell them what you have, motor, battery etc and see what they say.

 

[GreenLantern]

An electric motor can become an electric generator. Has anyone in the forum any insights into converting a hub motor to a generator. I am thinking of a powered rear hub with a regenerating front hub. I don't imagine that much power would be generated but could a constant trickle charge be helpful?
Your thoughts and comments are welcome.

 

[amberwolf]

Here's a nice long thread offering many similar ideas, with discussion in various tones and levels:
http://www.diyelectriccar.com/forums/showthread.php/alternators-free-energy-perpetual-motion-over-13449.html
It's an idea that occurs to many people that don't yet fully understand electricity, motors, and energy usage/losses.


It comes down to: yes, you will get energy out of the generator, but it's not free, since you are taking it out of the motor via the road surface, you're just slowing yourself down and using up your battery *faster* than if you did not do so. Basically all you are doing is running a belt (road surface) between the drive wheel and the gen wheel, trying to couple power from one to the other, *plus* drive the vehicle forward. Takes more energy to do that than it does to just drive the vehicle forward.

If you are only using the generator for regenerative braking, well, it's pointless, since you could do that with the original motor, without the weight and cost of the second motor and controller.

 

[GreenLantern]

Thanks for your informative reply amberwolf.

 

[xsi6]

Ya know I don't think this exact idea has ever been discussed on ES.While it's true your always gonna lose If you try regen while motoring along on flat ground (every friend I tell about my EV interests says "Charge as you go " ? ) but if you hang around here (ES) you will find out quickly it can't be done. but in Pa where i'm from there are a lot of hills and thats where this idea could work. I started thinking about this when i was reading about the Rabbit tool/Sanyo motor controller combo (I'd post a link but i forget where, it was one of bigger ebike stores they sold a lot of C-lites and stuff )anyway they said their hub motor worked better as a generator than a motor, with the controller set up for maximum regen. I'm no engineer but from what I've read here a dedicated hub motor/controller combo could feasably capture a good deal of the energy lost from climbing hills as well as enhanced breaking capabilities.

 

[amberwolf]

Except that with any controller that supports regen properly, there's no need for a second hub motor just for regen braking; it's just extra mass to accelerate, and extra resistance to keep overcoming while moving.

If you already have one hubmotor on the bike, and it does not have a freewheel in it, and it's controller supports regen, you have all you need to do this right now.

If something in the system doesn't support regen, it would be typically easier (or at least more efficient) to remedy just that part than to add a complete secondary system solely for regen braking.


The one case I can imagine adding a second hub to make some difference in braking would be if your motor hub is a rear motor, and you wanted better sudden hard regen braking from high speeds--a front hub motor would brake better than a rear solely because of the weight transfer during braking. But if this really is an issue, then it would still be more efficient to replace the rear motor with a front one, unless you simply want to have two complete motor systems on the bike.

The extra motor power might be useful if you have heavy loads to haul or big hills to climb, regardless of which motor does the regen braking (or if both do).

 

[pgt400]

I did this with a 48v 1000 w golden motor and the result was excellent. Only requires rectification of course. My motor is about 8 rpm/volt so even at low RPM you get good output. There are some youtube posting showing hub motors as generators.

 

[LI-ghtcycle]

I am thinking out-loud here, I know that it would be good to have regen in my main motor to help with braking (this will mean no freewheel at the motor, as I will be using it as a "mid drive" powering the rear wheel directly) and I have also had a dilemma about how best to have a front wheel with a non-skewer QR axle (I hate QR, the springs fall off to easy, I'd much prefer bolt on axle), and I have seen where many are using generator hubs these days.

I can get a built generator hub that is 6V 3W with double wall rim for $100 (of course it has QR though .. ugh!) so I am thinking, maybe I could have a really simple solution to regen for my little SLA that will power the motorcycle alarm and just be a general "crowd pleaser" to show and tell.

I'm not looking at this as a way to replace regen for my main motor, just something to compliment what I have already, and do it very simply.

OTOH, I am going to get one of the "mini max" type front hub motors (same as Falcon EV sells) to play with, and I wonder if I should try using that and wiring it to a regulator? I have no idea how this would work exactly, but I know that it could work in some form or fashion, but it might not be practical?

Thoughts?

Thanks!

 

[John in CR]

Any electricity you generate other than recovering energy during braking is a drag on the system and a reduction to overall efficiency. If you want some ooo's and aahhh's for something that isn't a negative, put some solar panels on your bike, even if they're only enough to charge your alarm battery. Please don't impress the gullible with something that can only lead them to believe in above unity scams.

 

[LI-ghtcycle]

Don't worry, I won't be selling flying cars or "H20" fuel cells anytime soon, but when it's cloudy or otherwise not the best day for the solar panels, I would think it might be a nice thing to have to pump up the alarm battery.

I just thought that might be a simpler easier method than trying to get a controller set for regen to try and accept input from the front hub, and maybe it's a fools errand, that is why I ask you all here. 8)

 

[neptronix]

Yeah, the hub motor is going to drag on the bike while it's in regen.. any motor generating electricity is going to create drag. And regen is less than 50% efficient, so you'd be wasting energy.

Cmon man, you should know this

 

[LI-ghtcycle]

Ok, how about this? Any easy way that I could rig up the front hub to only regen as a brake? Maybe that would be too complicated? I would think it might be possible to have it set up to go into regen mode with the main motor, but IDK these things. :wink:

 

[neptronix]

You could do that, but the motor would still drag you down constantly. if a controller is connected to a DD motor, it is doing a bit of regen at all times, it's also heavy rotating mass that you don't need if you're going for efficiency if it's only going to be used as regen.

It would seem as if there was a net energy gain to be had, it would be very small.

You already have a nice DD motor, why don't you just use that at high voltage and/or amps to get the speed you want, rather than a mid drive hub + a DD hub on one of the wheels?

 

[MadRhino]

To make it any worthwhile, you'd have to be able to freewheel the small front hub, and engage it only in braking. Then, even if you can get rid of its rolling resistance, only carrying the weight of it would still imply some power loss.

I have to agree, that your best regen route is to use the motor that you already have as mid drive.

 

[vintagerider]

has anyone considered using a gear-less, brush less front hub motor to generate power sort of like re-gen but all the time? how much of a drag does one of these motors generate when rolling, i seen a video on u-tube of a guy powering up some lights by spinning the wheel by hand, i think he was using some sort of three phase rectifier or maybe just generate when going downhill possibly activated by front brake switch would this extend the range or would the added weight, nullify its usefulness, i had this idea when i first came to this forum, thinking i would see this idea debunked or tried, hey i am new to e-bikes so take it easy if i don't fully understand the demographics. i know one of you brainiacks knows the answer. forgive me if this has been talked about before

here is the link to video http://www.youtube.com/watch?v=OD1gSx92DuM

 

[dogman dan]

Yes, it's been considered. But not after doing the math. It's close to the category of perpetual motion. Because of electrical losses to heat, it's far more efficient to pedal a bike with no motor, than to pedal up power to run a motor. But you can do it, a dd motor is a generator too. Some have made wind generators from bike motors.

Internal gearmotors that freewheel are the answer for people who want to pedal some, motor some. They can pedal the freewheeling motor easily for as far as they choose, then use the motor just to get up a steep hill.

Building a bike with regen is a fine idea though, it's just not worth it to pedal up that regen. But if you ride up hills enough, regen to capture some of the power on the way back down is fine. Regen just to add to your braking power is a great idea.

It could be cool to use a bike that had regen you could switch on and off. I don't know of one, but I'm thinking of an internal gearmotor. It would freewheel normaly, but have a switch that could electronicly engage a clutch lock. With the locked clutch the motor could then make power down a hill, then the clutch would be unlocked for normal pedaling. The use would not be to run a bike, but to provide power for other things. Like keeping electronic stuff topped up on a long bike tour, lights, music, phone, etc.

They used to make 6v bicycle light generators that friction drove on the tire. Perhaps one of those would be best for that small recharge purpose. Lighter than motor hubs. Pedaling with on of those on the bike was a real big resistance. Really amazing how much pedaling it took to keep that little bulb bright.

Likely better to charge small electronics with a small solar panel in the end, if you were touring in the boonies.

Like the little light generators, pedaling through regen on a dd motor varies with the speed. Very slow and low power is fairly easy. Try to ride faster than 15 mph pushing regen is a son of a bitch. Much harder, the faster you spin the generator.

 

[E-racer]

LOL at perpetual energy comment! Totally true! Remember, your main motor would have to output more horsepower than the regeneration wheel can recover. There's always efficiency losses when converting forms of energy.

 

[vintagerider]

yea thanks Dogman i seen the posts after i posted this was going to delete but you chimed in, interesting idea surprised nobody has tried this on there bikes, i like the geared motor idea as everyone seems to be ditching these for gearless could probably get on for cheap to try, may be just to power up lights and heated jacket or hand grips, on a separate battery, as these can soak up a lot of juice, would require lots of know how to do the switching and charging on-demand, and wouldnt it be cool if you could switch it to a drive wheel going up steep hills and hit the brake on the way down to regen and added brake effect, wow two wheel on demand would take advanced engineering for this

 

[Drunkskunk]

......wouldnt it be cool if you could switch it to a drive wheel going up steep hills and hit the brake on the way down to regen and added brake effect..

You can, many Direct drive motors have a regen function. for various reasons, they can only recover a small % of your power, but as a brake they are very effective.

 

[E-racer]

If you drive accessories off a generator you will use more power out of the main battery than if you just hooked the accessories to the main battery to begin with. Every time you convert electricity into torque you loose energy through various losses. If you take torque and convert it back to electricity you've doubled your losses.

 

[vintagerider]

this has given me a idea when i build my bike to use a small, light , geared motor on the front wheel and batteries and controller on the triple clamps, not a lot of batteries as i will only us when a steep gradient off road happens, the added weight may even stabilize front end a little. it will free-wheel when not in use and help on braking this beast down-hill, still up in the air about using hub-motor on rear or mid-drive for my build, the regen may not be worth it but for a billy-goat climber for brief periods may be the answer than overloading and overheating a single motor, may be better for longer range as the gearing would not be so low to handle hills because of the helper front motor, could use a ratio for longer distance and slightly higher speed

 

[E-racer]

Sounds good. Just remember for the money it costs to add a second motor and controller you could build a larger main battery or run a higher powered mid drive or rear hub setup.