Gas Motor -> Direct Drive Motor for Regen power back into Battery

[markz]

How much gasoline power, in terms of engine displacement (cc's) would it take to obtain regenerated power from mxus 3kw back into the battery?

Bikes hub motor wheel will be lifted off the ground then a chain attached from motor to freewheel.
Long distance trip with the custom trailer with its telescopic stand acting as a stabilizer/stand.

Choices are
Trimmer motors are roughly 30cc *get anywhere, classifieds/stores
Them gasoline bicycle motors are 2 stroke 65cc, and the 4 stroke are 40-50cc. *order online
Hazard Frought/P.A. has 80cc, 140cc, 170cc, 200cc+ *which has a sale on right now which is what I'm leaning towards.

 

[amberwolf]

You'd need to know the loading; how much current, at what voltage, are you trying to get out of it. So, how much power total, so you have some idea of the power (hp) the ICE needs to be able to output; that should lead you to the approximate size of ICE to start with. (you can always just use a bigger one than you need, so you're not running it as hard as otherwise)

Then you figure what speed the motor has to spin at to generate the voltage (under load) required to be higher than the battery voltage, so it will create current flow.

Then you figure the gearing needed to make the motor spin at that RPM from the ICE's RPM at the speed that lets the ICE output the power you want.

You can experimentally determine some of this if the ICE doesn't have documentation to help you figure it's powerband. I think you can use http://ebikes.ca/simulator to determine the motor end of things.

 

[dogman dan]

Id call it much easier to just carry the tiny generator, sold at harbor freight in the US. It will comfortably run a 300w charger for sure. Get one for about a hundred bucks, and fire it up at camp, or while you ride.

I do get the idea though, and it will work I think, with a similar 50cc motor, should be enough size to run your wheel as a 500w generator. This is a guess, but its based on the same little motor can put out 500w continuous on that tiny generator.

As AW said, it would just be a matter of putting that belt on the pulley to drive your motor, and then setting the throttle to a speed the motor can do easy enough, and then see what you get in watts from the motor. With a heavy regen going, it might be you have to turn the motor pretty slow for the little motor to handle it, so think in terms of gearing that thing down to a 10 mph rpm with the drive belt pulley. If that's not enough volts, then you might need a bigger motor than I think. Again, making that generator a simpler solution.


I keep saying belt drive, because I think that would be easiest to build, and use intermittently, than a chain drive. Simple tensioner tightened up when the motor is in use.


Mostly it comes down to how fun the idea is to build for you. If that's fun, do anything the harder way. I like that fun too, but only to a point. I often like a simple solution, like carry a 30 pound generator a bit more.

If you go to a 100 cc motor, uhh, what is the electric wheel for? There is also, a relatively light 2000w generator, about 50 pounds.

 

[markz]

My original idea was a generator, and I have found some neat little older Honda units, two are 300W so 2.5A on 120V so will work with ONE dell laptop charger I have, spits out 7.5A @ 20.50V, another is Honda 600EM max is 8.3A on 120V, I think it should do the trick. Its the sweet spot for size and weight otherwise 1000W+ genie is too much. 14.4 inches long and 9.84 inches wide, stands 12.8 inches tall and has a dry weight of 41.9 pounds.

If I can find a cheap small trimmer motor or cheap lawn mower then I will get a regen cont and go to it. It'd be interesting to see what them 30cc trimmers do, amazingly small and light!

Id call it much easier to just carry the tiny generator, sold at harbor freight in the US. It will comfortably run a 300w charger for sure. Get one for about a hundred bucks, and fire it up at camp, or while you ride.

I do get the idea though, and it will work I think, with a similar 50cc motor, should be enough size to run your wheel as a 500w generator. This is a guess, but its based on the same little motor can put out 500w continuous on that tiny generator.

 

[dogman dan]

Yeah, definitely do it for the fun. I had one of those 800w Hondas till it finally sucked a valve and died. 4 stroke was nicer, but it weighed a ton. The cheap 2 stroke generator I replaced it with is definitely lighter, and has worked good now for almost 2 years. So it was a good buy at 90 bucks on sale. Loud, stinky, just like a weed whacker would be.

But those homebrew gassers still fascinate me. A guy near me has one, must be at least 50cc, because he flies 30 mph on it all the time. Very simple, motor on the rear rack, v belt to the left side of the wheel, and a clutch on the motor I think. For sure it would drive a smaller DD motor generating, I'm just not sure about a big motor with lots of regen resistance. If you can dial the regen in to your liking, it would work fine, if the motor won't turn fast enough with a tiny motor.

I was about half way ready to buy a honda motor gas kit instead of more batteries, to run my long cruiser bike. But I veered back to electric and bought some more lipo.


I only mentioned the 2000w generators because you were talking about larger motors. I just bought one of those for my RV, Its quite light for its power, and very quiet. Very tempting to rig some kind of trailer, and run that thing through a big fat power supply to a motor. I have one of those 60v 1000w chargers around. That would move the cruiser along pretty good too.


But on the other hand, when I want to go long distances, this works pretty fine.