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Forum Index : Windmills : f&f Windmill high volts low amps problem
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| jtiner Newbie  Joined: 14/04/2014 Location: United StatesPosts: 3 |
I am new to this forum and the backshed site. I have just built a vawt windmill based on the savonious design. I am using an 36 pole F&P style motor, that I had originally rewired to 4x3 then back to factory specs,with an automotive alternator rectifier diode to convert the output.Testing it with the multimeter, after conversion back to factory specs I can get up to 40 volts hand turning the mill. However when connected to my charge controller (coleman air 440 amp) with someone manually turning the windmill I only show an output of 0.5 amps max. I thought I could get at least a 10 - thirty amp charge. What am I missing? The meter on my controller is digital. Does that make a difference? I am wondering if I have reconnected something incorrectly. Any advice is greatly appreciated. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi jtiner, welcome to the forum. 0.5 amps hand turing may be ok, need some more info. About what RPM was it turned at, and at what battery voltage? 30 amps from hand cranking isn't going to happen unless you've got Arnold Schwarzenegger to help. If its a 12volt battery, at 30 amps, then your cranking in about 360 watts. For the average person, 100 watts is about all we can make with our legs, much less with our arms. To get 30 amps from a F&P, at 12v, your also going to need some serious RPM, over 400 RPM at a guess. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| jtiner Newbie Joined: 14/04/2014 Location: United StatesPosts: 3 |
Rpm is probably between 30 and 60 hand turning. Battery voltage is 12. Please keep in mind that I am a newby but a quick study. I have noticed that the wind does not seem to turn it much faster. I'm sure I need to change the location if I intend to catch more wind. Based on your reply it seems that it may be working as should be expected. If I could get a few hundred watts in 15-20 mph winds I would be pleased. I'm just not sure what I should expect.I started on a caps mod but maybe I should work on getting the basics right before adding such a mod. With the way it seems right now, I have built a big 12 watt windmill. I am open to links to study. I have read through the f&p rewiring guide and the caps mod on the backshed site. My blade design is a combination of the 55 gallon plastic drum savonious design and pvc pipe vawt from indestructible. Gizmo, thank you for your reply. Any further references or advice is appreciated. |
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Don B Senior Member  Joined: 27/09/2008 Location: AustraliaPosts: 190 |
Hi jtiner, If I understand correctly, you ate only trying to test your device by hand turning. You will never get any significant output at this speed. Do not be deceived by the voltage that you measure when hand turning. With no load, the voltage will always be high, but then try it again with a load connected and it will drop considerably. As it is a savonius machine, it should be capable of turning at a useful speed when exposed to the wind. It is only at these sorts of speeds that you will begin to get a useful output. You note that you have re-connected the stator back to its original configuration. This will give you a higher voltage output but, as soon as you connect a low voltage load to it, the high winding impedance will seriously limit the current output. You need to use a connection arrangement that will give you more current (and hence more load on your turbine) when it is running at speed. Regards Don B |
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If you can connect a larger size electric drill to the shaft you will get a decent reading. Even better still is if you access to a lathe, mount the shaft in the chuck and spin it at the desired speed. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
http://www.thebackshed.com/windmill/FPRewire.asp Its all a big experiment!, although it says 1x12C would work for your type of mill, it doesnt say at what voltage. If spun by hand at 60rpm and you get 40V then this will be way too high for a 12V battery. to get 400rpm out of your savonius turbine probably unrealistic, hence rewire for 2x6C as thats easy as pie will double your current or more. likely you'll end up with this as it says, great all rounder 3x4C or 4X3C Also note that with no way to limit the output, it will eventually self destruct in the right wind, having your alternator better matched means you can load the turbine better and that self destruct windspeed will be higher. note that ontop of these combo's you have the 42pole stator in 3 different windings, my turbine was great with dual stators 100 stator 1x14 and 80S as 2X7C into 48V but that was a 3m diameter turbine for a swept area of 7m2 I havent found your turbine but for example if it were 2m tall and 2m in diameter it would have a swept area of 4m2 which is just more than half. (Its more complicated than this but you get the idea) to make meaningful power, you need BIG turbines unless you mount it on the top of a speed boat. EDIT: F&P without going to NEO magnets and all kinds of hard work is good for 250-300W, after this it gets tougher to get bigger power as iron losses and other factors are at play call it 250W and at 14V the best you'll do is ~18A, as someone else said this is you running flatout on an exercise machine. Makes you realise how much energy we use on a day to day basis when you're cranking the handle by hand good luck! Luck favours the well prepared |
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| jtiner Newbie Joined: 14/04/2014 Location: United StatesPosts: 3 |
Thank you very much for your feedback. I wasn't sure I was going to get a reply. I am very grateful for your advice, each one of you. Bob: So, I gather that rewiring the motor will give me a better power output. The more coils in parallel groups(2x6c, 3x4c, 4x3c etc), the higher the amps, providing start up rpm speed is attained. I guess the trick is to find a balance between the stator configuration and average wind speeds for my area. I want to be able to generate a significant charge in 15mph winds. But I don't want to have to wait for a thunderstorm with high winds. I think my diversion charge controller with diversion load will provide an electric brake from over voltage in high winds. Karlj: This is a link to the windmill I have built: http://www.instructables.com/id/55-Gallon-Drum-Turbine/ However I have added more wind catching surface area on the top barrel. I have also built what I call a 'hat' that fits on top. I built it out of an old water cooler squirrel cage fan blade with a 6 foot blade span 3 inch pvc 6 blade construct attached to the top of the squirrel cage fan. Not sure the squirrel cage fan contributes much but the pvc blades add leverage and slower start up speed. Madness: Thanks for the testing tips. Thanks again, now I have a direction to take this project. JCT |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
biggest problem with this is the lack of swept area and inherant drag at higher speeds. You're looking for a low speed stator config and max 200W in a howling gale realistic numbers in the order of 4-5A at 12V this assumes you have a decent site and is a thumb in the air based on others experience here. I'm a big fan of swept area= power! Luck favours the well prepared |
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