I'm looking for the cheapest most effective way to build a water wheel that will work good evn at a low rpm to charge a battery that will power a light bulb. And just in case best case scenario i am able to charge the battery faster then the light bulb can draw from the battery I need to know how to divert extra electricity to another battery. Thanks all

 

Hard to beat an automotive type alternator for hobby projects.

 

So I'm assuming I will convert the alternator to permanent magnetic motor (that being said, do you recommend any specific alternator for this?). And can I hook it up directly to a battery? If not what do you recommend? And once the battery is fully charged how do I divert the extra elec to another battery? Thanks!

 

Any modern car alternator already has rectifiers in it and a regulator to prevent overcharging. Water wheel, pulley, belt, pulley, alternator, battery, light bulb.

 

Don't alternators need to spin a certain speed in order to maintain the field?

 

Yes they do. The typical Delco 10SI and 12SI one wire units need around 2500 RPM to self excite but will stay up and running down to 1200 - 1500 RPM unless they have a low RPM stator put in them.

Then those numbers can usually can go down to about half that but the peak output current is considerably lower.

 

I want to get as much electricity as I can. But I do like the idea of connecting a modified one wire alternator to a battery. Now, what about a load diverted for when my battery gets fully charged. I don't want to lose any electricity. Do you recommend anything?

 

Use enough batteries to absorb all the energy.

You see, "divert" and, "not lose any electricity" are mutually exclusive like, "catch enough fish to eat" and, "not decrease the current population".

 

Use enough batteries to absorb all the energy.

You see, "divert" and, "not lose any electricity" are mutually exclusive like, "catch enough fish to eat" and, "not decrease the current population".

Run a pump to put the water back.

 

The best thing to use is low rpm motor. Like the one in treadmill. I think they are low rpm permanent magnet motors.

You can use alternator, but there is no way you can make it spin fast enough. Normally most cars idle at 900 rpm. You will be lucky if you can get a couple hundred rpm.

 

Using a low RPM water wheel, would work if you could get the RPMs faster using gearing.....however, you'll lose some power through friction in the gear train.
Just like when I was living/working, in the Industrial Revolution.

One main lineshaft to power several other machines.
Manually shift pulleys and jack shafts, to change speed.

For the low price of $26,000,000.00; I'll do your calculations for you.

 

If you get an alternator wound for 24V and swap in a regulator from a 12V alternator then you will be able to charge at lower rpm so long as 12V is still enough to saturate the rotor field which I suspect it would be.

 

Automotive alternators are poor matches to most wind or water projects because 1) they need power to energize the field windings and 2) they're designed for much higher rpm than is practical. This is why people rewind alternators for lower rpm and use permanent magnets to make the fields.

For a constantly-powered water wheel, you can maybe overcome #1. As long as the total power being generated exceeds the consumption in the field windings, you're good. But if the flow is unreliable, a big problem for windmills, you need some way to shut down the field windings during idle times.

IMHO, you won't find a practical solution to #2 because you would need to gear up from, say, 30 rpm up to maybe 6,000 rpm. That's a 200x gain and I don't think that's practical.

 

an alternator is more dfficient thhan a dc motor, the permanant magnet field makes the armature hard to turn even with no load on the generator. rpm prolems can be solved with pulley ratios, alternator turns faster than water wheel.

 

Ok so in using a treadmill motor as a generator. Do you recommend any specific battery that would be best for being charged by that motor?

 

So backwards thinking! You asked for, "the cheapest, most effective way". You don't accomplish that by building a random voltage generator out of a motor that wasn't designed to be used as a generator and then go find a battery to absorb the power. You decide how much voltage you need first, then design the generator to fit the battery.

It's not nice to waste our time designing, "the cheapest, most effective way", then change the requirements.

 

Interesting look: www.scotthydroelectric.com
Book: Producing Your Own Power. Rodale Press. but does not cover generatqrs.

 

I need 250volts at most.

 

And i will only need to power something for at most for 14 hours.

 

The first thing I would have asked after your initial post would have been how many volts, amps and power do you require?