Building a Bike powered Battery Bank?

[320touring]

Based on a thought formed in this thread (http://ecomodder.com/forum/showthrea...ork-31589.html) I'm considering setting up a stand to allow me to charge a battery whilst cycling on stand..

Looking for some advice and observations on my thoughts so far-

Intention would be to set up the stand with the rear wheel of the bike driving the input shaft of an alternator, with a feed to the battery. Reso for wheel drivennis to allow removal of the bike for riding when the weather is ok!

To get a decent charging voltage out the alternator, i reckon it needs to be spinning 2000rpm minimum.

A 26" wheel does 130rpm at 10mph

It works out that a 26"wheel and tyre is about 28" all in, giving a circumference of 88inches.

16:1 ratio means that the alternator needs to have a circumference of 5.5".

So if the alternator has a wheel of approx 1.5-1.75" diameter we should be good.

Practical considerations i could do with your assistance on:

1. Should I build in a diode or battery charger to smooth the output, or will the alternator / battery be ok with just the voltage regulator on the alternator?

2. What sort of battery would work best? My initial thoughts are deep cycle-but they are damn expensive..

3. What would be the best method for getting the power in a usuable form to the house? The bike is in my shed, and the output needs to be 240v AC. Intial thinking is a dc to ac transformer fed off the battery, linked to a dedicated socket in the house.

I'd appreciate all your thoughts on this

Cheers

[SwamiSalami]

niiiiice! I've been wanting to do something similar, but have an inverter that plugs directly into the wall rather than use a battery system. I actually picked up a stationary bike for free off of craigslist a few months ago. I'm not sure what exactly this entails as of now, bc of time restrictions, but I do know that I'm starting off in a good place---the display panel is powered solely by the pedals!

Anyway, can't wait to see what you come up with. best of luck!

[ksa8907]

I have looked at something similar, i wqs turned off from the idea when i ran the numbers.

Humans can produce about 1/4 HP. 746w × .25 × .6 (efficiency) = 112w

At 15 cents/kw you would have to log 10 hours of ride time to save a dollar.

[Xist]

Originally Posted by ksa8907

At 15 cents/kw you would have to log 10 hours of ride time to save a dollar.

Well, how much would you save on medical expenses?

[California98Civic]

You definitely must use deep cycle batteries. I am told they can be had cheaper at Walmart, but the quality would be inferior, likely, to an Odyssey or something similar.

[ksa8907]

Originally Posted by Xist

Well, how much would you save on medical expenses?

Due to riding a bike or generating electricity?

[California98Civic]

Originally Posted by ksa8907

Due to riding a bike or generating electricity?

Due to generating by riding the bike.

[changzuki]

The idea of a bicycle generator is a topic that often gets some attention here at 9 Main during a home tour. I've had several units (alternator based, permanent magnet motors, etc) and to generate power into a battery bank is not easy - this comes from someone who could at the time, generate 300 watts continuous for 2 hours. Most folks who are not dedicated cyclists will likely never see that type of output.
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A second unit exists but you'd never know it to look at it. This unit has the ability for the operator to recharge its on-board 48 volt lithium batteries by going down a hill and engaging the regen switch, or by jacking up the rear tire off the floor and pedaling:
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Like the in-house unit, this is not at all easy to do, but if you're in really good shape it can be done.
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A cycle generator is a fun project and it can get you in shape while making some small amount of electricity to charge batteries or run small appliances. Beyond that, don't expect too much.
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~CrazyJerry

[ksa8907]

Originally Posted by ksa8907

I have looked at something similar, i wqs turned off from the idea when i ran the numbers.

Humans can produce about 1/4 HP. 746w × .25 × .6 (efficiency) = 112w

At 15 cents/kw you would have to log 10 hours of ride time to save a dollar.

Sorry, my math is wrong. 10 hours would get you 15 cents and 70 hours would get you a dollar.

[Occasionally6]

My thoughts on this:

Use an alternator - that gives built in voltage regulation.

"Right size" the alternator. They have efficiency curves in the same way ICEs do. Something like 12V (14V) at 30A would be about right for most people. Look at lawn tractors and forklifts trucks for that size.

A simple test of human power capability without expensive test gear or energy conversion losses is to measure the rate of climbing stairs in a high rise building. Knowing the height climbed (measure the height of a single flight and multiply), your body mass, gravitational acceleration and the time taken you can calculate the power required:

P(W) = [BM(kg) * 9.8(m/s^2) *h(m)]/ time(s)

The alternator efficiency - power in to power out - is likely somewhere around 60-65%.

Charging a battery results in energy conversion losses. They're probably around 70% efficiency, in and out, so ~50% round trip. Better to use the power produced directly if possible.

Rather than convert the output to mains AC, I have at least one TV that runs off a nominal 12V with a transformer in the power supply to the mains. That draws ~30W. PCs usually have an internal 12V power supply. There are adaptors for charging devices off automotive accessory sockets etc.

I'd still use a battery to act as a buffer because the human power will vary and likely be intermittent. The size of the battery will be determined by how fast it can accept a charge. An SLA might do it.