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Forum Index : Windmills : cheap chinese mill 12v to 24v??

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rgormley
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Joined: 22/02/2006
Location: Australia
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Posted: 10:03am 03 Mar 2009

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i have one of those 12v 250watt cheap chinese mills

http://cgi.ebay.com.au/EnviroWind-Wind-Turbine-Generator-200 w-watts-200-w_W0QQitemZ350169537497QQcmdZViewItemQQptZAU_Bus iness_Industrial_Farming_Agriculture_Farming_Agriculture_Equ ipment?hash=item350169537497&_trksid=p3286.c0.m14&_trkparms= 66%3A2|65%3A1|39%3A1|240%3A1318

with a smaller blade set on it. has been running 24/7 for 3 years or so....

is it possible to simpley mod the internals to change it from a 12v to a 24v

or would i have to rewire the coils??

anybody had some experiance with these mills?

GWatPE

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Joined: 01/09/2006
Location: Australia
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Posted: 11:38am 03 Mar 2009

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The 12V mill will probably be good for 24V with just a capacitor voltage doubler added in parallel to normal rectifiers, for low end cutin boosting. The mill will probably produce more power as well. I would use the electrolytic non polarised audio caps. You will require 6 caps of around 100-200uF, 100V and 4 x 10A bridge rectifiers, wired in the manner as has been described elsewhere in the cap thread. I have 6 x 2x33uF, 100V, NP electro audio caps as a voltage doubler on my mill. There is more heat in the diode bridges than the caps. I have measured a couple of degrees above ambient at full power.

I know these mills can produce over 700W with the right loading. You may need to look at the controller upgrade as well.

The frequency of the chinese mill is approx 1/4 of the F&P, so the caps need to be that ratio bigger than the ones I used. The caps are not expensive, $2-3ea.

If you go this way, post some feedback.

Gordon.

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rgormley
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Posted: 12:36am 04 Mar 2009

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hhmmm!!! very interesting.... lots of reading to do...

thanks, will post some feed back if i proceed....

rgormley
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Joined: 22/02/2006
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Posted: 12:40am 04 Mar 2009

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could you please give me the link to the thread on this cap/rec mod

i had a quick look but could not find any specific information.

Thanks,
Richard

Steve9R

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Joined: 24/01/2006
Location: Australia
Posts: 72

Posted: 02:14am 04 Mar 2009

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Yes i have one of these mills..

you dont need to get caps for it.. the mill itself is a simple 3phase motor and you have 3 x wires (one for each phase at the bottom).. simply wire them into 3 standard bridge rectifiers (or two if you're really tight!). and straight into your battery.. just make sure you have dump circuits off your regulator for excess power drain..

mine puts in up to 8amp @ 24v no problems..

the bridge rectifiers you can buy from DickSmith for about $6 each..

they are 600V 35A rectifiers and look like : http://www.westfloridacomponents.com/DI022/35A+35+Amp+600V+B ridge+Rectifier+GBPC3506+Single+Phase.html

Steve

GWatPE

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Posted: 03:19am 04 Mar 2009

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Hi Richard,

Yes you can directly feed the windmill straight to a 24V battery instead of the 12V one, with the same rectifiers, as mentioned by Steve.

If you go the little bit further, with the capacitor voltage doubler that is shown here on this page, around 2/12/08, you will end up with a machine the produces power in low winds and high winds, instead of just in the higher winds.

Gordon.Edited by GWatPE 2009-03-05

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rgormley
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Joined: 22/02/2006
Location: Australia
Posts: 245

Posted: 10:24pm 04 Mar 2009

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so based on having a 12v mill and feeding into a 24 volts bank.....

i connected the mill last night to my 24v bat tbank when the wind got up i saw around 5 amps (so around 120 watts)

NOW if i add a cap/rec doubler what UF value should i be using and what the safest lowest voltage rating on the caps

i can get 12 x 100uf 300volt from our work store

but can i say use the 220uf/470UF 63v caps from jaycar/disksmith?

GWatPE

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Posted: 10:40pm 04 Mar 2009

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GWatPE said I would use the electrolytic non polarised audio caps. You will require 6 caps of around 100-200uF, 100V and 4 x 10A bridge rectifiers, wired in the manner as has been described elsewhere in the cap thread.

rgormley said i can get 12 x 100uf 300volt from our work store

These will be OK. Are these polarised, DC caps, or AC rated, non polarised.

start with 100uF, and check the mill response. If it seems to respond quickly to to the changing winds at the low levels, then double the cap size, and compare.

Gordon.

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rgormley
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Posted: 11:31pm 04 Mar 2009

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the 100uf / 350v caps are normal elecrolytic polarised DC caps

GWatPE

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Posted: 01:30am 05 Mar 2009

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If you use DC rated caps, then these need to be connected in the back to back arrangement, and this halves the effective capacitance. 470uF caps are suitable, and you will need 12 of them in this arrangement. *

The voltage doubler is sized, to deliver approx a maximum of 10% of the max rated power of the windmill.

Gordon.Edited by GWatPE 2009-03-06

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rgormley
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Posted: 06:15am 07 Mar 2009

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i wired the doubler up
2 x 100uf 350v DC electrolytic caps back to back (as per the diagram
http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?T ID=1138&PN=1&TPN=15

in low winds (all we have had lateley) i got NO amps
i did apear to boost the volts as i measured upto 51 Vdc (no load) from the cct. Got a "crack" on the batt leads when connected to the batts.... but alsas NO charging current....
i think the "crack" i got was simply the caps discharging
the 2 x 100uf back to back will give me 50uf yes??
maybe i need to start with 2 x 470uf ???

i will try when the winds gets up (need a liitle faster "spin" in think!!

Edited by rgormley 2009-03-08

GWatPE

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Posted: 09:03am 07 Mar 2009

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Hi Richard,

here are the caps and rectifiers I put together for the voltage doubler on my F&P mill. These were 66uF[2x33uF,100VAC, from Jaycar] F&P frequency dictates smaller caps, approx 1/4 the size of those required for a 500W chinese mill.

the caps I recommended to use were 470uF, so yes the 100uF are 1/5 of the necessary size.

More importantly with the setup, did the windmill change how it responded to the wind when the doubler was connected. ie, did it slow down when connected.

What is the minimum current you can measure with your meter?

The caps do dissipate power, so it is important to not glue them together tightly. I use hot melt glue on the larger can type caps, where the gaps are quite large, and only to tack the caps together at the ends.

On my mill, I have measured current from 10mA up, once cutin is reached. for example, today I checked mill cutin at 40Hz [approx 90rpm], and by 50Hz [110rpm], the current was 0.2A [6W]. by 60Hz [130rpm], the current had increased to 0.4A [12W]. This is all power that would not normally be captured as cutin would be at approx 170rpm.

more wind and bigger caps will provide a better result.

Gordon.

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