How would I build a battery generator/charger?

Not sure if this is the right place, but basically, I'm looking to charge up some portable battery banks by using an indoor exercise bike.
If anyone here has done something similar, please show some examples. I'd like to do something myself if it's easy enough for beginners. Or are there affordable kits out there already just for this purpose? Thank you.

Try search "Bicycle Chain Charger USB" on Amazon.
I like the "28W Solar Powered Charger" better,

glockboy said:

Try search "Bicycle Chain Charger USB" on Amazon.
I like the "28W Solar Powered Charger" better,

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Thank you. When searching for it on amazon, I only get 1 type of $60 range charger. I don't know how reliable they are based on limited reviews.
Do you have any experience with these bike chain usb chargers?

I am also looking into lightweight solar chargers for hiking. I just figured why let all this energy go wasted while exercising on the bike? I should be able to charge a phone while trying to stay healthy. Seems like a win/win scenario to me.

I haven't used those bike chain dynamos. I have 2 reasons. First, the energy isn't free. It takes power from my chain, which I often desperately need to keep up with my wife, getting my destination, get home from work, whatever. To quantity it, I usually average somewhere between 200 and 300 W. To match a small sized solar panel, the Dynamo would need to steal 10 - 15W. I have spent huge dollars to increase efficiency by 6 percent!

Second, mechanical devices need maintenance, and they break. So do solid state electronics like solar and batteries, but there are fewer failure modes. I usually opt for simplicity, if I have a chance.

Look for some of the off-grid magazines and YouTube clips. Over the years I have seen several articles on converting things like car alternators to be driven by wind, water, and legs. The big problem is that anything that needs to rotate to generate electricity is very sensitive to rpms. In your case, it would take a good charge controller to keep the output at a steady usable level. Whether that is USB or 12/24/48v for a storage battery bank is your choice. Using an exercise bike will be a little easier to adapt than if doing it while biking around.

Another thing you might look into is there are still a few of the old-style tire powered bike lights for sale. I don't know what the voltage output was, but with today's electronics converting voltages is a lot easier than it used to be.

Good luck, and let us know how it turns out.

I happened to be on this site and remembered that they had several projects somewhat like yours. I just did a search for bicycle generator and found several entries. This is one of them.

http://www.instructables.com/id/Ultimate-10-Watt-USB-Bicycle-Generator/

I'm definitively no expert here, but a couple of quick thoughts...

It's true what Tomothybil mentioned, it's easy to be RPM-sensitive. If you can take a loss in efficiency, then you could more or less simply rectify the current, and dump it into an SLA-slab or even marine deep cycle battery. That would pretty much remove that dependency, and provide a steady working voltage for whatever you put downstream. It'd also decouple generation and usage of the power.

If you do want to go direct, rowing-machines could be interesting to look at. In order to simulate the speed of a boat, some of them use rotating ballast (not entirely sure what the term is), which could be an interesting place to tap in for power, at a more stable RPM, potentially.

Every exercise bike I have seen has had a speedometer, and it is relatively easy to add one to a regular bike. Some simple testing can determine an appropriate speed to produce the output voltage desired. Then it just becomes a matter of maintaining that speed.

Keitho said:

I haven't used those bike chain dynamos. I have 2 reasons. First, the energy isn't free. It takes power from my chain, which I often desperately need to keep up with my wife, getting my destination, get home from work, whatever. To quantity it, I usually average somewhere between 200 and 300 W. To match a small sized solar panel, the Dynamo would need to steal 10 - 15W. I have spent huge dollars to increase efficiency by 6 percent!

Second, mechanical devices need maintenance, and they break. So do solid state electronics like solar and batteries, but there are fewer failure modes. I usually opt for simplicity, if I have a chance.

Click to expand...

I didn't think about adding that might add resistance.
Yeah, in your case, it totally makes sense to use solar panels. If that amazon bike usb charger is my only option, then I might have to forgo this whole thing. It would probably take a decade to break even charging my phone and it definitely looks like it'll break in under a year.

Looking at the other posts, it looks like this might not be a simple/cheap project as I originally thought.
I didn't know it would require a certain RPM. I thought as long as you made a full rotation, it can still charge slowly or quickly, depending on your speed. I'm guessing this is also true for those hand crank emergency radios which I also need to look into for a purchase.
Thank you everyone for pointing me in the right direction. The DIY method might require a lot more research for this person with almost no experience on the subject. Appreciate the help.

You absolutely do not need a constant RPM if you buffer with a lead acid battery, you pretty much just need to generate any kind of current, and things would work out.

That said, it still holds true that DIY would be quite some work.