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Forum Index : Windmills : Small windmill to keep 12V battery topped

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Woodie
Newbie

Joined: 22/10/2008
Location: United States
Posts: 2

Posted: 09:06pm 21 Oct 2008

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Hi, new member here but have been lurking for a while reading much and understanding a little ;-)

I am looking for recommendations for a small windmill (blade or vawt) to build. Intended use is to keep a 12V battery topped off in my trailer when it is not in use. When I park the trailer, the battery is usually fully charged since it charges while I am driving, but it may sit for months without use and I would like to keep the battery topped off during that time.

Wind powered charging is attractive since I have no power in the shed the trailer is stored in. My wind conditions could be described as normally having a 5-8 mph breeze with windy days in the 15-25 mph range. We have winter storms that approach 50-60 mph gusts. I also felt this would be a good first project to establish an understanding for future, larger projects.

So, I am looking for recommendations for this idea. I am pretty handy, have normal tools available as well as a 6x14 lathe. I can scrounge pretty well too, my wife thinks I am too good at that tho!!!

Thanks in advance for ideaa, recommendations or directions to articles about other peoples solutions.

Don Edited by Woodie 2008-10-23

Robb
Senior Member

Joined: 01/08/2007
Location: Australia
Posts: 221

Posted: 03:17am 22 Oct 2008

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How about something like this

I wish he had more details on the dc to dc converter but its a start.

Solar is good from a no moving parts point of view.

Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 01:53pm 22 Oct 2008

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Don, in your case a small solar panel on the shed roof would be far more practical.
Why? solar panels can be regulated so they never overcharge your battery, the regulator simply shuts off the current flowing to the battery and the solar panel does not mind.

With a wind generator you HAVE to use some kind of a dump load when the battery is full or some kind of secure mechanical brake that stops the thing turning. You can't just disconnect the battery as then the wind generator has no load and might run amok.

But, by all means go about tinkering with wind generators, its great fun even if there is no immediate practical use for one.
That's the case at my place at the moment, my VAWT is almost complete but the only eventual use for it will be powering a modified chest fridge (for drinks) once I get hold of a suitable inverter/ charger for the battery bank and provide alternative mains power for the fridge.

Klaus

Woodie
Newbie

Joined: 22/10/2008
Location: United States
Posts: 2

Posted: 02:12pm 22 Oct 2008

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Robb and Klaus, thank you for the input. I cannot use a solar panel in the current storage location due to significant shading. I tried that and it was not successful due to lack of available direct sunshine.

I like the system Robb showed above and I am certainly capable of building it tho I was unaware of the load shedding requirement you mention Klaus. Guess I need to check that the load shedding now......

Don

Dinges
Senior Member

Joined: 04/01/2008
Location: Albania
Posts: 510

Posted: 01:57pm 24 Oct 2008

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It's not the kind of answer you expect (or want to hear) on a windenergy forum, but I too would opt for the PV panel option, even with the shading issue you have. It's likely much easier to solve the shading problem (best case: start the chainsaw and do some pruning. Worst case, you may have to install the PV panels on a mast) than it is to design, build, install and maintain a windgenerating system. A windgenerating system consists of

1) a generator (the easy and fun part to build)
2) a turbine (blades) (only fun to build if you're Oztules and you have a chainsaw)
3) installing a tower (won't you have a 'windshading' issue in your current location as well ?)
4) building/installing a diversion controller and dumpload
5) installing and adjusting all of the above so it works reliably
6) maintaining all of the above so it keeps working (which takes likely more effort and time than hopping out to the place and simply recharging the RV battery with your car every 2-3 months)

Off-topic, but the longer I'm messing/reading with/about windpower, the more I realize it is not the solution for me. With judicious use of solar for space and water heating I can probably push back my own (external) power use to about 1-2 kWh/day (from a previous 11 kWh/day, currently at 6 kWh/day, of which 3 kWh/day for water heating).

So I'd still strongly recommend a small PV panel, perhaps on a mast to overcome the shading problem. Quick, simple, easy and (yes!) cheap, compared to building and maintaining a wind generating system. If you're having a solar shading issue I strongly suspect you will also have a wind shading issue. Windturbines need to be installed on high masts to work properly. Why not skip the hard part of building a windgenerating system and build/install a (small) mast and install the PV panel on that ?

Also, the practical implementation of 'trickle' charging depends on the size of the battery; you don't state the capacity (Ah) of your battery, but it makes a difference whether you're trying to trickle-charge a 12V/7Ah gell-cell or a batterybank of the size as used in diesel-electric submarines. Both can be tricklecharged, but one needs a much larger windturbine/PV panel than the other.

Edit: on a different note, how about simply removing the battery and taking it home with you ? That's what we normally did with the batteries in the boat, as they're not used (and thus, not needed) in winter. And that way they can be properly stored and taken care of at home. Also makes theft (or illegal occupation) of the trailer a little less convenient and easy.Edited by Dinges 2008-10-26

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