Building a pedal power bicycle 12 volt generator, ghetto style

[james]

too bad you are not nearby, I have many semi-operational batteries around here.

[Daox]

James, feel free to introduce yourself in the introductions forum. If you have any ongoing projects post em in the projects and improvements section. We'd love to hear about what you're working on weather it be the solar setup, ways to conserve or whatever.

[jwxr7]

Originally Posted by MetroMPG

It was funny though: when the bulb expired, the pedal effort immediately became easier. But powering the light certainly wasn't "hard". I wish I could have taken a current reading to know how many watts I was pushing before it blew up.

That's pretty cool. I'm pretty sure my 6 volt 1 million CP bulb says it's supposedly 55 watts on the base of the bulb. We could use Ohm's law to estimate the current if you know the voltage just before it blew (assuming the bulb really uses 55 watts at 6 volts). 55 watts at 6volts is 9.2 amps. That puts the bulb resistance around .65 ohms. So at 8 volts it was drawing around 12 amps. That puts power levels just under 100 watts.

[jwxr7]

I just remembered that I used my spotlight to load test my pv panels while they were still 6 volt output. I think the bulb ended up being a much lower load than the stated 55 watts, but don't remember how much lower. So the calculations may be a bit generous .

[MetroMPG]

I never thought of checking the bulb: so I just did, and it says 25w.

It blew out at 8v, which works out to 3.1 amps.

[MetroMPG]

Originally Posted by james

too bad you are not nearby, I have many semi-operational batteries around here.

Thanks! But... I just got one:



Man, I love this town. So friendly.

Second garage I went to had a pile of batteries in the corner. The owner was happy to let me pick one out (quick voltmeter auditions) after I told him what I was doing. He seemed interested.

Found one that read 12.3v, and figured that'd likely do. He said it probably just needs charging, and that people occasionally came in and insisted on a new battery, even though they didn't really need one. He even insisted on putting it on his load/capacity tester before I left. (It rated around the "50%" mark, but it's only 50% charged, so I don't know how that affects the test).

And it's less than 2 years old! Probably in better shape than my car's battery.

I paid him the scrap value ($10), which he said he'd give back if/when I return it.

[jwxr7]

Originally Posted by MetroMPG

I never thought of checking the bulb: so I just did, and it says 25w.

It blew out at 8v, which works out to 3.1 amps.

Don't sell yourself short .
The wattage of a fixed resistance like a bulb, isn't constant when voltage changes.

If it's 25w at 6 volts, that means It draws 4.2 amps (25w/6v) at 6v, so the resistance is around 1.4 ohms (6v/4.2A). Use this resistance to find the current at 8 volts. It comes out to 5.7 amps (8v/1.4ohms), so it ends up being around 45w at 8 volts (8v x 5.7).

[jwxr7]

I really like this project . It's made from stuff most people would have lying around. Wood is my favorite prototype medium , and it sounds like it is turning out some useful power.

[MetroMPG]

Jamie - thanks for schooling me on the basics. You'd think by now I'd know a bit more than I do, eh?

I agree the wood is a super quick way to get an idea off the ground.

Well, it works! (Again. This time @ 12v)

It puts out a little less juice than I was expecting/hoping, but here's what I'm seeing while pedaling, connected straight to the 12v battery (which had a starting voltage of about 12.33).

Total "system" voltage on the left, amps on the right..... fast, faster, fastest:

[james]

Thats awesome that it works. I am going to have to do this here. How much trouble is it to take the blower fan out of a metro? My friends have one sitting in the yard, but its 0 degrees outside, and I'd rather wait till it warms up, especially if it takes more than a few mins.