Generator to Battery question

Solar Expert Posts: 402 ✭✭
Ok, I'm back into my mad scientist super kludger mode now that the weather has turned cold and was thinking about building a 12vdc windmill generator ala mad max style (ie, all mechanical, no electronics) and I had few questions. Mostly I'm trying to understand how the wiring should work on this to make it function as intended. Or at least how I want it to.

The system I'm doing is pretty basic using a hand built old school mechanical voltage regulator to regulate how the battery is charged, and a 12v automotive blower motor scavenged from another project which will be used as the generator. Now what I'm trying to figure out is this. When you connect the motor to the battery, it's + to + and - to -. That of course will turn the motor (it'd do that anyways, even if it was a generator, afaik), which in turn burns battery power.

Now, my thinking is, based on how I understand this, that if I have the voltage regular as part of the circuit, that transfer of power would be arrested until such time as the generator was producing enough power to trip the first of the two mechanical circuits on the regulator. So once circuit one is live, two would be as well, and would then produce the battery drain situation I mentioned. Or at least I *think* it would. Or would that regulator prevent backflow? Or better yet, would the spinning motor absorb the difference and still charge the battery? Also, is there a specific way I'd need to wire all of this to get the best performance?

The point here is that I want this to work just like the more modern windmill generator systems do, but with an entirely mechanical method. Sure, ok, it really has no practical purpose per say, except as a fun experiment, and something to occupy my time now that the crops are in. It's one of those "just for the heck of it" projects. So, any thoughts?

PS, I'm thinking that the wiring would look something like this. I'm only guessing at this because for some reason this all confuses me (which it shouldn't, but it does. Go figure).

Loop 1: Generator+ -> 1st coil (regulator on/off coil) -> Generator-
Loop 2: Generator+ -> 2nd coil (regulator, voltage) -> battery+ -> battery- -> Generator-

• Banned Posts: 17,615 ✭✭
Re: Generator to Battery question

Look at an ordinary automotive generator & mechanical regulator circuit. The ignition switch supplies power to the field windings. When this is off, no current flows to the windings so the battery does not discharge. The armature supplies current to the battery through the regulator on a basis of Voltage differential. With the system off the armature has no Voltage so no differential and no current flow.

But you are trying to use a motor as a PMA. You can't shut off magnets. You have no commutator to convert the AC power produced to DC. Without semi-conductors these two things become problems.

Have you considered playing solitaire instead? :roll:
• Solar Expert Posts: 402 ✭✭
Re: Generator to Battery question

Interesting information. One question, wouldn't a DC motor produce DC current? I can see an AC motor producing AC current, but not a DC producing AC.
Re: Generator to Battery question

A brushed motor (Universal) looks just like an old car generator--Except that the current path for the armature and field windings are connected differently (there are series/shunt/etc. connected brushed motors, and the field is separate from the armature in a genset).

http://en.wikipedia.org/wiki/Electric_motor

Then you get to AC motors--Which are a whole science in itself (I learned of a new type here just a few months ago)...

And there are servo motors, 3 phase AC motors with electronic commutation (DC computer fan motors, etc.). Some need exciting (external power for the rotating field, others have permanent magnets, and then the standard induction motor which the rotating field produced by the stationary windings induces currents in the rotor (induction)--Which then provides the N/S magnetic poles for the stator windings to "pull" the rotor around (note, you can generate AC power from one of these motors--Get then started on AC grid power, then apply torque the the motor shaft and try to turn it faster than 1,800 RPM (if 1,725 RPM motor)--It will start driving electricity out to the grid.

http://otherpower.com/otherpower_wind_alternators.html

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Banned Posts: 17,615 ✭✭
Re: Generator to Battery question

As Bill said, not all motors are alike.

You should start by driving the motor with another motor and see what you get out of it: AC or DC and what sort of Voltage & current it is capable of. It may not be suitable for your experiment, and it's best to find that out before you start trying to regulate its output. Otherwise you could wire up a whole system you think should work, then go mad trying to figure out why it doesn't.
• Banned Posts: 1,807 ✭✭
Re: Generator to Battery question
Interesting information. One question, wouldn't a DC motor produce DC current?

Usually they do, yes. All motors (or generators) produce AC power in their windings whether it be permanent magnet or wound field. DC motors typically have an ingenious mechanical rectifier in the form of brushes and commutator.
--
Chris
• Solar Expert Posts: 402 ✭✭
Re: Generator to Battery question

Thanks for the info guys, and sorry for the delay in replying. It seems that everyone around here thinks that, since we've got our work done, we're fair game as "volunteer" labor for everyone else. Ah well, it happens. But I'm glad you guys are pointing this out. Now to answer the question of why I'm even bothering to do this, it's more a question of, why not? lol. I've learned some pretty incredible things about stuff I didn't know simply by doing experiments like this. Even though they have no practical purpose, they do provide a learning environment, and that's what counts.
• Solar Expert Posts: 114 ✭✭✭✭
Re: Generator to Battery question

Steve,
We are about an hour south of you in Indiana and just finished our harvest today.
Anyway, in between us is a big Amish community which like to use PM commuted generator windmills to charge their buggy batteries.
Drive through there on a windless day and you quite often see windmills just a buzzing away.
They don't get them disconnected when the wind dies and they motor on the battery.
• Solar Expert Posts: 402 ✭✭
Re: Generator to Battery question

Yeah, ours came in pretty quick this year. We have several farms in the family and when harvest time comes, it's all hands on deck. Of course, this year we got lucky. A) we had a lot of outstanding favors we called in, so we were able to call them in and get 3x's the normal amount of equipment on hand to bring everything in, and our stuff was ready ahead of everyone elses. Total crop wise it's less than last year but still above average.

As for the project, well, it's still one of my "rainy day" projects for something to do. But between a neighbor (formerly known as dumb***) burning his horse barn to the ground (no casualties, save for a 90yo antique barn) and a huge project at work (big rush dev job worth lots of \$\$\$) I've been pretty much slammed. But I'll get back to this when I get the time. On a side note, one of the local geniuses pulled off something that I think is rather neat. It's another one of those famous "for the heck of it" projects. Anyhow, he tied together a bunch of yard lights and created his own little solar farm. The most interesting part of his design was that he figured out a way to step the 6v the lights made up to 12v and successfully charge a car battery. ^_^ Again, it's a pointless project short of being something to kill time and be somewhat of a learning experience, which is basically what I'm after with my project.