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Forum Index : Electronics : Wind Charge Controller
| Author | Message | ||||
Percul8or Newbie  Joined: 09/08/2010 Location: AustraliaPosts: 13 |
I have put together a charge controller that works well. I thought I might share it here. http://percul8or.blog.com/2013/12/29/wind-turbine-charge-con troller/ |
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powerednut Senior Member  Joined: 09/12/2009 Location: AustraliaPosts: 221 |
Intersting design. Thanks for putting in all the reference links too - it really helps newbs like me understand the electrickery better. Could you explain how/why your using thermistors as a dump load? I thought they were normally just used to detect temperature changes. |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
Hi Powerednut, Thanks for your inquiry. I'll put up the thermistor setup shortly with an explanation. All this is external so by increasing thermistor "capacity" you can put this on any size turbine. Re your question, Nope, thermistors are just resistors that decrease (Negative Temperature Coefficient NTC ones)resistance as they heat up. They heat up as more current passes through them. So they are perfect here. Steps: Battery gets to full voltage relay switches current from turbine goes through thermistors they heat up so resistance drops and more current passes through them Load increases on turbine Turbine slows so less power generated thermmistors start to cool Balance found and turbine turns slowly as it can't overcome load of thermistors The key is to select the right value (ohms) thermistor and ones with sufficient capacity. |
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| powerednut Senior Member Joined: 09/12/2009 Location: AustraliaPosts: 221 |
Thanks for explaining. That makes sense to me and should provide a nice smooth balance. It had not even occurred to me to use them in that way - mostly because I've used them as sensors. Do they react quickly enough to deal with high wind + gusty conditions? |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
Hi, Thermistors are used widely on such things as soft motor start to prevent initial surge currents. Yes they react quickly. The magic is the higher the wind/gust the more they heat up and the quicker they stop the turbine but still gently. The circuit includes a 5-10 minute delay so once braked it stays that way. Very handy in gusty conditions. As an added bonus the delay capacitor takes some time to charge fully so initially when battery is close to fully charge it tends to go above and below charge threshold. So delay is shorter at first and then as battery stays longer above threshold the delay stretches out. Range is about 5-10 minutes. And if solar is floating the batteries, the brake just stays on. All good. |
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| domwild Guru  Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Sorry, I believe the link is broken. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
what link? PCB's now completed and site tested. For sale for $25 inc freight Note these PCB's can be used for any voltage comparitor circuit so you can build your own design around it. I'll post some pictures of bare board and completed PCB FYI |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
oh this link....sorry 
Link |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
PCB picture now posted at end of blog |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Thanks for that. The link works for me now, strange. Thermistor is a good idea for a smooth brake. Have seen an article which used ultracaps to store fluctuations in wind speed rather than wasting the energy but such a setup will need to divert at some stage. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| RetepV Newbie Joined: 17/10/2014 Location: NetherlandsPosts: 4 |
Hi, this is an interesting idea. But I am missing a key bit of info. What is the rating of the thermistors that you use? I.e. how many Watts should they be able to dissipate? I read that it's limited to 600W turbines. You have 2 thermistors per phase, 6 total. So I guess that the thermistors need to be able to dissipate 100W each. This is just off-hand, thinking while I'm reading. :) I feel that if I do the math, it will turn out to actually be a lower power. The resistance starts out high (10 ohm or so), and goes low as the NTC's heat up. Then the power from the generator goes down as the turbine is slowed down. So the NTC's will never have to dissipate the max power of the generator. Let's see if I can make a simple Excel sheet to make some approximations. :) Or maybe make a simulation. |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
Hi RetepV, Good to get emails from overseas. The thermistor brake can handle virtually any turbine power output. You just add extra thermistors. I would love to see your spreadsheet or simulation results. But you are correct, the thermistors heat up very quickly, slow the turbine down and then just stay warm even even in a strong wind keeping the turbine braked. FYI the initial thermistor value (@25degC) depends on the turbine voltage. For example for 24v systems I use 2 x 10 ohm in parallel (total 5 ohm) on each phase. |
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| RetepV Newbie Joined: 17/10/2014 Location: NetherlandsPosts: 4 |
Hehehe, we have one thing in common with Australia: a mostly flat country and lots of wind. :) Well, I'll make an attempt at simulation during the following weekend, so I beg for a little patience. ;) But you didn't exactly answer my question on the max power dissipation of the NTC's. I see NTC's up to 15A. But I can imagine that the heating and cooling cycles shorten the life of the NTC's. So I would think that for longevity, you would need some beefy NTC's that can stand the heat. |
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| RetepV Newbie Joined: 17/10/2014 Location: NetherlandsPosts: 4 |
Also, theorizing, the NTC's should not be mounted on a heatsink, as that would influence their response to heating up. |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
Try climbing this mountain and see how flat Australia is 
Mount Kosciuszko I use these. Although only rated at 5.1 watts each (30 watts total) they have an inrush current of 7.5 amps (45 amps) Epcos 10Ω 5100mW NTC Thermistor, 100s, 21 Dia. x 7mm There appears to be NO degradation due to heat after many years. Also a heat sink would defeat the purpose as it would delay them heating up. On one test unit I added a small 24v DC fan that came on with the brake directly cooling the thermistors and that worked very well. Regards, Perc |
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