Bicycle power (bike generator)

[gwillen]

Does anybody have experience with building or buying a system for generating (and storing) power with a bike?

I see a couple of pre-made ones for sale:

http://pedalpowergenerator.com/
http://www.econvergence.net/electro.htm

I don't think I can beat the second one for the price of the bike stand plus dynamo. But it seems like they are way overcharging for the "12 vdc regulator", at $235 -- shouldn't something like this suffice? http://www.solar-electric.com/ss-20l.html (A charge controller intended for charging deep cycle batteries from solar cells.) It's admittedly only rated for 20 amps, which is below spec for 400W of bike power at 12V, but research suggests I'm likely not capable of making 400W with my legs.

For storing energy, this very forum suggests my best bet is two 6 volt golf cart batteries, hooked up in series.

For feeding energy back out, probably an el-cheapo cigarette-lighter inverter (I understand these are 'modified sine wave' inverters?) like this guy: http://www.google.com/products/catalog? ... 7632061747 (It may end up that we're better off just getting all our lighting/sound/etc. in 12VDC, and getting a 12VDC regulator.)

I'd love to hear from someone with appropriate experience for a system like this:

• Can I combine these components safely in the way I desire?
• Can I use that charge controller to safely charge 2x costco 6V golf cart batteries in series? Will cell balance be an issue?
• If my frantic pedaling somehow miraculously produces more than 20 amps worth of juice, will the charge controller explode? Can I design the system to sink the excess power safely, without doubling the cost to get a 35 amp charge controller?
• Does the charge controller obviate the need for a blocking diode (sounds like it should?)
• How does one connect the actual load (the inverter or 12VDC regulator) in a system like this? Straight across the battery?

Thanks, electrical engineers of Burning Man!

[BBadger]

No, don't use a solar voltage regulator for your charger. The most basic of solar "regulators" are just large diodes that prevent current from discharging into the solar panels like a one-way valve. More advanced ones simply make sure the batteries charge at a proper rate. Solar regulators don't need to care much about voltage because the solar panels don't have high voltage, and provide energy mostly with a fixed voltage and a supply of current.

The dynamo regulator used for your bike is more concerned with the voltage aspect of your generator. The dynamo creates a higher voltage (like 60V) that must be "stepped down" to a lower voltage appropriate for your batteries (12V). To do this it usually uses a more expensive step-down DC-DC converter to efficiently generate usable power for charging. You could also use a cheap-ass linear regulator circuit to step down your voltage, but that would waste a ton of power, which would in turn just waste your leg energy.

You just have to bite the bullet and buy a real charging regulator. Think of it this way: the reason you're dragging that bike to the playa is to generate electricity; using a cheap-ass regulator will dramatically reduce how much energy you can generate. So if you don't want to buy a decent charger, you might as well just drag more batteries to the playa instead.

For your questions about exploding charge controllers: just make sure you buy a good one. They're usually rated for high wattage anyway. Those lead-acid batteries will work fine so long as your charger is "smart" which it should be. Any extra power will either be converted to heat or simply make pedaling easier (it gets harder to pedal the more energy you're producing).

You can probably just buy an inexpensive blocking diode that they show in the diagram for cheap. I don't know why they're charging $90 (or $120 on amazon) for that thing. You can get your own, wire it up, and mount it to a heavy heatsink and you'll be fine.

[gwillen]

... Iiiiinteresting. I don't know why it didn't even occur to me that the bike dynamo would be putting out much more than the desired voltage.

Looking back, I see that the dynamo I inspected on Amazon ( is described as "12-24V", but then the specs say it outputs up to 40V. So, good call.

(Of course, in the meantime I've discovered the reason nobody ever does this: Gas-powered generators are about an order of magnitude smaller and cheaper than I thought they were. But this would still be a cool project, even if I now understand how impractical it is.)

[BBadger]

... Iiiiinteresting. I don't know why it didn't even occur to me that the bike dynamo would be putting out much more than the desired voltage.

Looking back, I see that the dynamo I inspected on Amazon ( is described as "12-24V", but then the specs say it outputs up to 40V. So, good call.

(Of course, in the meantime I've discovered the reason nobody ever does this: Gas-powered generators are about an order of magnitude smaller and cheaper than I thought they were. But this would still be a cool project, even if I now understand how impractical it is.)

Well, most power-generation projects at Burning Man in general are impractical--if only because you only recoup your investment if you're continuously generating power with whatever you bought. Solar power, in particular, is usually a poor investment on the playa, as a week of solar power a year hardly justifies the initial investment. Your bike charger is probably a better bet if only because it generates a lot more power quickly making it somewhat suitable for actually charging stuff.

Weigh the costs against just buying more deep cycle batteries though. For the cost of a "400W" bike generator ($340) alone, you could have 3-4 6V 200AH deep-cycle batteries. If you only discharge them to 50%, you'll get:

0.5 discharge x 3 batteries x 6V x 200AH = 6,480,000 Joules

If you were to pedal-power that:

6,480,000 Joules / 400W = 4.5 Hours

So will you be able to dedicate 4.5 hours (assuming it's at full pedaling power all the time) for charging your stuff? Do you need that much energy?

Gasoline generators are probably the best investment for power needs on the playa. You're only burning what you're using, and if your generator sits unused the rest of the year at least it's not losing value or degrading in quality. Make sure you get a decent one, usually a Honda EU variety. There are really cheap ones at Costco and such, but those Hondas are well built and there are parts everywhere for them.

[Elliot]

All right, I'm out of my depth here, but I do know this: You can get an inexpensive General Motors automobile alternator that puts out around 14,5 Volts for charging a 12 Volt battery and requires only one wire to be connected (plus a jumper on the alternator itself). I used one on my hot rod car -- works great.

Hot rodders love these because they can be used on any car, no wiring complications. They call this a "one wire alternator" and you can buy a shiny new one, but it is simply the old standard GM alternator WITH A MARINE REGULATOR. The marine (boat) regulator is formally called a Self Exiting (or some such) regulator. I seem to remember it said "SE" right on it. The regulator is an internal part of the alternator, but not difficult to replace for a fair auto mechanic.

Any decent auto electric shop should be able to sell you the marine regulator (or a boat shop!), and you can get the alternator itself at an auto junk yard. Or maybe get the complete alternator from a boat shop or boat junk yard. Hmmm... maybe try eBay for "one wire alternator".

Just my 2 cents, of course.

EDIT: I see now that eBay is full of this stuff these days. (In my day, this was black magic. ) The one wire regulator costs around $15,-. Example:
http://www.ebay.com/itm/DELCO-10SI-12SI ... es&vxp=mtr

[Foxfur]

Bear in mind that the top physical energy output from a human (in good shape) is around 700 Watts, just shy of 1 horsepower.
I'd suggest upping your H2O intake and doing it in the shade.
Actually, I'd suggest using wandering burners to do it for you.
Offer them enticing incentives such as booze, food, or a happy ending.
You could then say that you convert bacon into electricity to power your luxuries.

[BBadger]

That's a good idea, make others want to pedal power recharge your shit. Maybe put in a meter that shows how many watts you generated and give prizes for the amount of joules produced.

[Simon of the Playa]

http://www.k-tor.com/

[gwillen]

That's cool, but the pedal-powered one doesn't exist yet, and the hand-powered one only produces 10 watts. Can't run much on that.

[FIGJAM]

[youtube][/youtube]

[gyre]

missing the important part -
What are you trying to do?

[gwillen]

I am trying to gain 1) personal amusement, and 2) something like 200-400 Wh of juice per day, to run basic lighting in the evening and maybe some low-key sound. But if I don't get it, we'll Burn in the dark; we've done it before.

[theCryptofishist]

Fair enough.

[gyre]

That's a lot of power.

The most common systems for this type of power run small tvs and basic lighting, 9-13" tvs.

As you probably know, the most important thing is maximizing efficiency.
There is generation loss and conversion loss going back to ac power.

Keeping everything DC would help.

Fluorescents are your most efficient source, though i don't have stats to compare elwire.
Types vary in efficacy.

There may be diy approaches for a generator that are worth your time, especially if space is not a premium.

[gwillen]

It doesn't seem like that much power? Note that I'm quoting Wh, not Ah; at 12V, it's about 15-30 Ah per day.

Definitely the goal would be to run DC lighting if possible. Sound would probably be AC, but small cheapo speakers draw 5-10 watts, so not a major drain.

The video FIGJAM posted looks really interesting. It doesn't account for the battery cost, but it convinces me that I could build the stand out of wood instead of buying one, which will save something. The dynamo is harder; using a motor for it, in the video he's getting like 20W. The good bike dynamos you can buy claim hundreds of watts. (Probably you can't actually _get_ hundreds of watts from pedalling, but they're surely more efficient.)

[gyre]

That's a lot of power from pedaling.

Why wouldn't the sound be DC?

[gwillen]

You're right, it would be. Don't mind me.

One of the bike systems I was looking at claims 3-400 watts; at that rate, it wouldn't be too bad. In this thread someone claims 50 watts, which would be less good.

[gyre]

You might get some useful figures from electric bike forums.

Most range from 250 watts at the hyper efficient end to 500 watts consumption.

[nixiebunny]

Curious project. Lots of downsides and no upsides that I can see.

You won't be able to make 400W for very long, unless you're a Tour de France type of rider. You'd be lucky to make 100W for 4 hours.And you'll be doing a very boring activity, chained to that bike.

For the cost of the bike generator, you can buy a 75W solar panel and charge controller. U?se your car battery, sicne you can't get enough energy in a day to require golf cart batteries.

Then, use that bike energy to pedal yourself around the playa, checmking out all the great art and fine naked people, while the solar panel back at camp does all the work.

[gwillen]

As an update, this is now off the table, because we gained a campmate who has a friend he can borrow a solar-panel system from. Free solar is a clearly an improvement on what I had in mind.