Building a pedal power bicycle 12 volt generator, ghetto style - Page 3

MetroMPG · 01-15-09, 05:59 PM

So I couldn't resist. I figured I'd give it a try since I happened to have a one of those million candlepower rechargeable 6v flashlights sitting right beside me. Popped the bulb out, hooked it up and presto! A million candles courtesy of my legs.

Funny: I could see the light pulse on each down stroke of the pedal. I'll have to wear my bike shoes and clip in if I want to apply smooth power all the way around.

So then I hooked up the voltmeter to see how much the physical effort corresponded to the output. And then it immediately became a game of "what voltage corresponds to what amount of light output", which immediately became a game of "I guess 8v is too much voltage for a 6v bulb". Oops.

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.

Next steps:

Commence the junk car battery hunt tomorrow!

Daox · 01-15-09, 06:23 PM

Quote:

Originally Posted by MetroMPG

And then it immediately became a game of "what voltage corresponds to what amount of light output", which immediately became a game of "I guess 8v is too much voltage for a 6v bulb". Oops.

I laughed at that part. Haha, who woulda thunk?

I think its really cool you could feel the difference with even that small amount of load vs no load.

james · 01-16-09, 09:50 AM

Yeah I couldnt believe how much the light I had on my bike slowed the bike down. And thats just a flashlight bulb! Really makes you think about how much energy is being used to power the typical house. You would need a team of cyclists riding 24-7 to keep it running.
Where should I post the info on my off the grid system?

james · 01-16-09, 09:53 AM

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

MetroMPG · 01-16-09, 12:55 PM

Quote:

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 · 01-16-09, 11:01 AM

Quote:

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 · 01-16-09, 11:13 AM

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

.

Daox · 01-16-09, 09:56 AM

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.

MetroMPG · 01-16-09, 12:47 PM

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.

jwxr7 · 01-16-09, 02:04 PM

Quote:

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).

01-15-09, 05:59 PM	#1
MetroMPG Infrequent noob Join Date: Aug 2008 Location: 1000 Islands region, Ontario, Canada Posts: 402 Thanks: 37 Thanked 20 Times in 19 Posts	And... it works! And... I already busted something! So I couldn't resist. I figured I'd give it a try since I happened to have a one of those million candlepower rechargeable 6v flashlights sitting right beside me. Popped the bulb out, hooked it up and presto! A million candles courtesy of my legs. Funny: I could see the light pulse on each down stroke of the pedal. I'll have to wear my bike shoes and clip in if I want to apply smooth power all the way around. So then I hooked up the voltmeter to see how much the physical effort corresponded to the output. And then it immediately became a game of "what voltage corresponds to what amount of light output", which immediately became a game of "I guess 8v is too much voltage for a 6v bulb". Oops. 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. Next steps: Commence the junk car battery hunt tomorrow! __________________ . To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-16-09, 09:56 AM	#8
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	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. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-16-09, 12:47 PM	#9
MetroMPG Infrequent noob Join Date: Aug 2008 Location: 1000 Islands region, Ontario, Canada Posts: 402 Thanks: 37 Thanked 20 Times in 19 Posts	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. __________________ . To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

01-16-09, 09:50 AM	#3
james Lurking Renovator Join Date: Jan 2009 Posts: 19 Thanks: 0 Thanked 0 Times in 0 Posts	Yeah I couldnt believe how much the light I had on my bike slowed the bike down. And thats just a flashlight bulb! Really makes you think about how much energy is being used to power the typical house. You would need a team of cyclists riding 24-7 to keep it running. Where should I post the info on my off the grid system?

01-16-09, 09:53 AM	#4
james Lurking Renovator Join Date: Jan 2009 Posts: 19 Thanks: 0 Thanked 0 Times in 0 Posts	too bad you are not nearby, I have many semi-operational batteries around here.

01-16-09, 11:13 AM	#7
jwxr7 Apprentice EcoRenovator Join Date: Dec 2008 Location: mid michigan Posts: 191 Thanks: 0 Thanked 0 Times in 0 Posts	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 .