A few stupid questions

[peter nap]

I've just become interested in wind generation and boy is there a lot to learn. I built my first unit last week from an elevator servo motor {115 V DC Var speed 2.2 Amp at 1100 RPM}.

I am a hobby blacksmith and had no problems with the mounts but as usual, I overbuilt the tail. After making two more I have a unit that tracks well. I have also made 6 different PVC Pipe sets of blades ranging from 8" pipe to 4" pipe and in lengths from 2' to 4'.

Surprisingly enough, it tracks, spins and makes electricity.

I haven't mounted it in it's final resting place yet where there is a steady 25 to 35 MPH wind. I have been testing it at home where we have had gusty breezes and I have measured up to 20 Volts DC.

At this point, I have a few questions.

I have no idea the amperage that it produces at 20 volts. If I remember correctly, for every voltage drop, there is a corresponding increase in amperage to supply the wattage demand. How does that pertain to battery charging through a charge controller?

Also....should I place my ammeter in line with the battery as a load or use a dummy load {No pun intended} of some sort.

I have read that the Harbor Freight charge controllers are persona non Grata but can't find any reference to the Controllers sold by Northern Tool. Any opinions or is there another Controller that I should use?

Thanks in advance!

[s4w2099]

If you dont know your motor's internal resistance then there is no use in doing math. What is the battery voltage???

I would suggest getting an ampmeter if you dont know any of these questions. If you are trying to charge a 24V bank then the current will be 0.

If the bank is 12V then:

I = (Mv-12)/Mr

Mv = open circuit voltage from the mill
Mr = mill's resistance

Remember to deduct the rectifier's and line's losses.

[peter nap]

Sorry..........I am charging a 12 volt bank.

I have ammeters. The question was if I should measure the amperage using a dummy load or the battery bank.

[Norm]

Use the battery bank....

         ( :>) Norm.

[peter nap]

Thanks Norm !

Any opinion on a charge controller. This will be left unattended for a week at a time at our weekend place,

[Norm]

In my opinion I would have a solar charging

system just large enough to keep the battery

bank topped off ....furl the windmill while

you're gone....you'll only need it while you're

there plenty of guys to help handle the charge

controller when you get to that part.

I'm more of a newbie than you are in this respect.

Just giving my opinion....not an expert.

              ( :>) Norm

[Seaspray0]

Without a dump circuit, it wuold be wise to take the generator offline if you plan on being gone for extended periods.  The generator has the potential to overcharge the batteries unless the excess is sent to a dump load.  This can happen while you are gone and the batteries are not being taxed.  Even a solar charger has the ability to overcharge but not to the extent a wind generator has... also, a solar cell will not suffer with a regulator between it and the batteries.  A generator needs a load to keep the blades from free spinning into high rpm's.  Solar cells are expensive and the most cost effective solution is to include a dump circuit                  

[peter nap]

Thanks Guys. I decided to take everyones advice and bought The Harbor Freight 45 watt Solar kit. With the panels I have up now, I should be able to charge my bank in a week.

I looked at a simple schematic for a dump circuit that I will build at http://www.s4wsbox.com/.

Any other circuits that I should look at before building one?

[commanda]

Just looked at the circuit by s4w; it has a major flaw.

The LM339 are open-collector output devices. This means you need a pull-up resistor from the output to the positive supply. As drawn, there is no path for gate current to flow to the fet, therefore the fet will never turn on, except by stray leakage (that is, if it does turn on, it is by accident rather than design).

Also not shown on that circuit; the LM339 is a quad device; the unused inputs all need to be connected to ground.