hydroelectric bike charger?
 

I'm planning a multi-day (maybe multi week) trail ride thru mountains. 36 volt lipo batteries. Checking out foldable and rollable solar chargers. Should work but slow, bulky, and heavy.

I have designed a small, lightwieght, hydro turbine that should work with a collapsable 2 inch plastic hose. If I find a stream with a six or eight foot drop, the gizmo should have sufficient power to continuously turn the bike's back wheel via a small auxiliary sprocket, once I set the bike on it's handlebars, or lift the back wheel off the ground with some sort of stand.

I understand that with the proper controller, the motor will work as a generator and recharge the battery. I believe this is the same as regenerative braking. If I camp beside a stream with a drop sufficient to turn the wheel all night, will that be sufficient to charge up the battery for the next day's riding? The wheel won't turn very fast, but it could run for 18 hours at a whack, assuming that I start each day at noon and ride until 6 pm or so. (I ride slow and walk beside the bike a lot on hills).

I would use this as my main charging method, but carry a small folding solar panel as a backup. Might take 2 days charging for 1 day riding. Does anyone have any other ideas for wilderness charging? I considered a small steam engine capable of running a 200 watt generator. That way, I could recharge anywhere with wood, water and an overnight campfire. A steam engine capable of running a 500 watt generator weighs about 50 pounds. This is way too much, even with a YAK BoB trailer. I see a lot of model steam engine kits; evidently hobbyists have been building them for a century or so. Anyone know of one that might fit this application? Can anyone give me more specifics on just how much power I would need to run a 200 watt generator? Can anyone tell me where to find such a small generator? Would an electric bike enthusiast in the SF Bay Area with more knowledge than I like to help a bit on this project? I could pay the right person for their help.

Thanx much.

Dave

How much water per second is going to be flowing through your turbine? That, plus the 6' assumed drop, would let us calculate the potential power available. Then we also need to know how much energy your battery pack will require for a recharge. You said it's 36V, but didn't give the A-hr capacity of the pack. The final input needed is the efficiency of the charging arrangement. That's partly a function of how freely the water flows (a long 2" hose will have lots of frictional loss if you're running a strong water current through it) and partly the characteristics of your motor when used as a generator.

But the water flow rate (say in lbs./sec.) and the A-hrs of the battery pack should at least give an idea of whether this is feasible at all.

I am skeptical that this will work. You have to put as much power into generation as you take out riding, and just visualizing it I don't see your hydro turbine producing that much power. You can put some numbers to it though by measuring the flow of water through the hose and turbine from the 6-8 foot drop. You can use the hydro equation Power = Height x flow x Gravity with the units watts, meters, liters per second, and meters per second per second respectively. Compare the watts you can produce against the watts you need for a charge.

hydroelectric charger
 

Thanks for the input. I'm not sure of any of the physical factors ncessary to figure the hydroelectric output; I'm just pretty sure that I can get enough power to turn the wheel continuously once the rig is set up. It's not a lot of resistance one feels when the bike is turned upside down and one turns the crank by hand. I'm sure that this amount of power could be had with a small fall and a simple turbine. I just wonder if turning the motor wheel under no load other than that put on it by the magnets in the motor would be sufficient to charge the battery. If so, would running it for 16 hours or so be enough to build up a full charge?

Dave

Since you don't seem to have enough information, I would suggest you find some forum (there must be one) on small water turbine generation. Then you could tell what kind of power you will be able to generate. I would guess there are people out there that have done these experiments and may have found better and worse ways of accomplishing generation of electricity.

Regarding solar, I would think you need a rather big array of panels. And full camp days between riding days for charging. The small foldable panels struggle just to charge a couple of AA rechargeable batteries (2-3Ah capacity each) over several hours of good sunlight.

--J