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chickenhawk
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Joined: 14/03/2013
Location: Canada
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Posted: 05:17am 31 Mar 2013

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Ok just getting into wind turbines. I have a small wind turbine ( home plans ) It is rated at 30 vdc and 8.5 amps. I built a wind turbine charge controller ( plans from the web ) and now I need help to find out how big of a dump load resistor I need. Please don't give me a long electronic story, all the amps -ohms-watts thing makes my head spin. ( give me my milling machine anytime). What I need how many xxx ohm resistors I need to wire in and I'm good to go.
Thanks

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 11:03am 31 Mar 2013

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Sorry mate, but you need to use the amps-ohms-watts thing to give a useful answer.

First up, is it a dump load controller, where it drains power off the battery bank?

If so, whats the battery voltage.

And whats the max amps the windmill can feed in at that voltage?

If its a 30vdc battery bank, and you mill can feed 8.5 amps, then to balance the supply and load, you would need a 3.5 ohm resistor, rated at about 300 watts.

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Downwind

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Joined: 09/09/2009
Location: Australia
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Posted: 03:16pm 31 Mar 2013

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I just wonder how you can actually build a successful mill without using "all the amps -ohms-watts thing" it makes my head spin trying to work out how you can do that without them.

Sometimes it just works

Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 12:01pm 01 Apr 2013

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Gizmo said

If its a 30vdc battery bank, and you mill can feed 8.5 amps, then to balance the supply and load, you would need a 3.5 ohm resistor, rated at about 300 watts.

That is spot on.

However finding a single ideal 3.5 ohm 300 watt resistor will be difficult, unless you make it up yourself.

You sound like a pretty inventive type of guy, so what I would do is hunt around looking for things with very high power heating elements inside, electric stove top elements, electric irons, hot water heating elements for example. Whatever you can scrounge.

Connect each in turn across your 24 volt battery and measure the current each draws with an amp meter. You may need to connect up several things together to reach a total of eight amps, but see how you go.

The big advantage of doing it this way, apart from cost ! is that 110 volt heating elements running at only 28 volts will not get that hot, and will be extremely reliable.

Cheers, �Tony.

Bryan1

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Joined: 22/02/2006
Location: Australia
Posts: 1345

Posted: 11:16pm 01 Apr 2013

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I made up my own dump load resistor years ago and its still going strong today. In the 6 or so years I've had it going only twice during the summer months I found it went open circuit.

Ok to make it I just got an old 240 volt AC water heating element and stripped the spiral wound ni-chrome wire from it. Cut lengths to suit the board I had made which has several bakelite risers on it. Then put one after one in parallel until I got the ohms down to around 1-2 ohms.

I was aiming for around 20 amps to dump and my clamp meter read 19 amps so when the dump load comes on it easily takes the 10 amps off the solar and if the wind is blowing again theres 9 amps to spare for my 1.5kw motor conversion. At times when a gale was blowing and the batteries were fully charged the dumpload was glowing red and no harm was done.

For a $5 item at the dump shop this has proved to be a cheap dumpload that has stood the test of time.

Regards Bryan

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