Low Amps

[oak leaf]

I hav built a 10' homebrew 24 volt gen. I am getting 24 - 27 volts but low amps (1 to 3 amps). I have run 100' of #10 wire to the gen. Can you please tell me what I have done wrong. Do I need to give you more info.

Harlon

[Flux]

"Do I need to give you more info."

Yes as always.

That 24 -27v is that battery volts or open circuit volts. If it is open circuit volts then you have no wind and that is the simplest explanation for low current.

If it is battery volts then it means very little.

The fact that you get something is usually an indication that the thing is working. If you don't have significant wind the you will get very little current.

I don't often encourage people to do this, but carefully open circuit the battery and measure the alternator volts ( dc after rectifier). If it shoots up to lots of volts quickly then you have wind and we might need to consider other factors. If the volts doesn't hit 40v pretty instantly and the prop speed doesn't shoot up then you have no wind.

If the volts and speed shoots up but the speed stays low on load with low current we may be looking at stall. At 3A your line resistance is not going to be much of an issue but it is likely to have to be taken into consideration if the trouble is not lack of wind.

I have a feeling that you are looking at about 8 mph wind and if you are not familiar with things you may think it is quite windy especially if turbulent around obstructions.

Flux

[Flux]

I think there is more information that would have been useful.

I have looked back at your previous posts and see that you were messing about with pvc blades. If you still have them then I think you will need a lot of wind to get anything useful and my estimate of 8mph may need changing upwards to 15mph or more.

Flux

[wooferhound]

I would wonder what size wire is wound in the stator ?

[oak leaf]

Flux,

Thank you for your reply.

The wind that I saw on my weather station was 8 to 10 mph. I have changed the pvc blades to fiberglass blades. I have seen a great improvement in speed of the blades. They do not start as well but when they do it looks good.

The stator was built with #14 guage wire, 70 turns. The voltage and amp readings I took were both before the and after the Rectifier. (So I checked both the ac volts and amps as well as the dc volts and amps).

I have put a diode in between my rectifiers and the batteries so I can read the output of the generator. The voltage on the batteries was 25.5 volts at the time of the readings I had given you.

I have a 500 ah string Batteries and a 3500 watt inverter on my system. I do not have near that much load on the inverter.  I did not get a chance to do what you suggested on the voltage test, I was called back to work last night, I will try to do that tonight.

We are expecting 30 to 50 mph winds this weekend as Ike will be coming to our town, we are in the Dallas area so we will not get super high winds but I hope to get enough to do some testing.

I will have my meters set up. I hope to get some good readings, see it furl, and hope to be able to shut it down before damage?

I hope I have now given you enough info to help me. My system may be doing what it is intended to do I just need wind? I have spent a lot of time and a good bit of money so far, I just want to make sure I am heading in the right direction!!

Thanks,

Harlon  

 

[oak leaf]

Wooferhound,

I used #14 wire, 70 turns.

Harlon

[Flux]

"I have put a diode in between my rectifiers and the batteries so I can read the output of the generator. The voltage on the batteries was 25.5 volts at the time of the readings I had given you. "

No that doesn't work the diode is pointless as you have the equivalent of it in the bridge rectifiers. The volts you measure when connected to the battery are clamped by the battery and will depend entirely on the dc battery volts. They are meaningless beyond cut in speed.

At 8mph you are probably just about there at 75W for 10ft. Just wait for the wind and see what happens before making any decisions.

If you are in a low wind area then you are not going to see a lot for your investment, If you get reasonable winds in the 12 to 15 mph region you will see much improvement.

Few people have any serious idea of the wind potential of their site so disappointments are probably common.

Just keep watching for a while and see what happens in real wind. We may be able to find ways later for you to make the best of what you have.

Flux

[Flux]

If this helps it should be a graph of power out for a 10ft machine with Cp = .2.

In low winds you may beat this, you will probably equal it at 15 mph but you won't get close in the high winds.