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Old 05-11-2010, 22:59   #31
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I think a wind generator controller needs a dump load to slow down the blades when you disconnect from the battery load.

I found a discussion on MPPT for wind generators.

MPPT controller for wind turbine - Page 3 - Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun

John
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Old 06-11-2010, 19:14   #32
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Think of the MPPT controller as an automatic transmission on a car.
With a wind generator, you're constantly changing the available power and the controller must constantly be "changing gears".
They're not made to do that as quickly as the wind load changes (in most areas).
The power available from the sun is generally more constant.
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No that's not the reason. Solar panels dint have a linear I/V output. There's a distinct " knee" where for a given sunlight the current is maximised for a particular voltage. The MPPT controller searches for and then tracks that point.

Wind generator have a much more conventional I/V output hence there is no mac power point and the use if a mppt controller isn't useful.

Dave
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Old 06-11-2010, 21:08   #33
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Wonder if you could run it into a capacitor and then somehow bleed power off the capacitor more evenly. It would still have to adjust up/down so as not to go outside the capacitors capacity. Perhaps it would take enough oscillation out of it so that an MPPT controller could cope??

Anyone?
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It would take an UNBELIEVABLY LARGE capacitor to do that.
Probably about the size of your boat.
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Old 09-11-2010, 21:16   #34
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"Can anyone quanitfy the statement "charge current up to 30% or more compared to conventional charge controllers"" Simply, yes.
Because an MPPT controller uses pulsed DC to charge batteries, and pulsed DC causes less boiling (less gas formation) in the electrolyte, it causes less of a resistance rise in the battery so the battery charges something like 10% faster.
And then, because an MPPT controller is taking excess voltage (typically, 17-22VDC from a solar panel, and your battery can only accept 14.4V) and converting it into extra amperage instead, the MPPT controller may deliver 10% more useable power (wattage) as well.
So a gain of 10-15% is very likely, 20% not impossible. "Up to 30%" is probably a bit of marketing hype.
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Old 09-11-2010, 23:07   #35
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I have been running 2 solar systems on my house in the rain forests of Washington's Olympic Peninsulaq for 8 years. One is MPPT, the other PWM. I'm on my 2nd MPPT controller and now run 100 vtdc. Ironically, at low power times the 20 year old PWM system starts earlier and stays charging later. The MPPT charges higher, apples and oranges. I opted for a Morning Star PWM for our boat do to size constraints. On the new boat I'm putting an Outback 60 MPPT cause I have the room and I will have enough panels to high voltage input the system making it the way to go. Smaller wiring and more system flexibility.
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Old 16-11-2010, 22:59   #36
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Thanks for all the good input. I currently have 2 solar arrays, one array is made up of 2 Sharp 80W panels and the other is 3 50 watt Siemens panels. Right now each array goes to a non MPPT controller, so 2 controllers. Would I benefit from ditching the two non MPPT controllers and going with something like a Outback mx60 MPPT controller? Or do I need to make sure all the panels are exactly the same to get any benefits of the MPPT?

Thanks!

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Old 17-11-2010, 03:58   #37
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Because an MPPT controller uses pulsed DC to charge batteries, and pulsed DC causes less boiling (less gas formation) in the electrolyte, it causes less of a resistance rise in the battery so the battery charges something like 10% faster.
And then, because an MPPT controller is taking excess voltage (typically, 17-22VDC from a solar panel, and your battery can only accept 14.4V) and converting it into extra amperage instead, the MPPT controller may deliver 10% more useable power (wattage) as well.
Sorry you're completely mixing up two things firstly MPPT is a means of determiningthe maximum power point of a solar panel this is needed because the I/V curve of a photovoltaic cell isn't linear. There is a distinctive " knee" where the cell delivers maximum power. That's the primary advantage of using mppt and it typically can deliver 20%+ over simple controllers

The charging mechanism, that is the battery charging part of a controller ( whether it's mppt or not) does NOT increase the system efficiency. PWM charging methods are not methods supported by battery manufacturers rather IUU or IUI is ( what's commonly known as 3 stage smart charging).

Most mppt controllers implement that method. As I said there's no efficiency gain but what is achieved is a faster charge rate .

Unless you're using small cheap panels, mppt controllers are always better as they exploit the characteristics of photovoltaics

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Old 17-11-2010, 04:11   #38
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Would I benefit from ditching the two non MPPT controllers and going with something like a Outback mx60 MPPT controller? Or do I need to make sure all the panels are exactly the same to get any benefits of the MPPT?
From what I have read on the sun-wind.com forum, the larger MPPT controllers
don't do well with a few hundred watts of panels. That forum is a very
good source for solar info.

I'm not sure about mixing panel sizes on one controller. Two Morninstar
Sunsaver MPPT controllers would work fine on two separate arrays and the
cost would be about the same as one Outback. Mavericksolar.com had real
good prices for Morningstar last year.

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Old 17-11-2010, 11:07   #39
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Im interested in hearing about the single MPPT controller used with multiple panels of differing wattages. I am looking to build a system with 4 panels. I was planning on using (4) 135 watt panels but may end up with something different. Would the Outback mx60 be the rigth controller for the (4) 135 watt panel array?
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Old 17-11-2010, 13:55   #40
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So I called Outback today and spoke with thier tech support. In my case, if i hook up a single MPPT controller to my panels as they exist now, the 2 80W panels would effectively be boruoght down to 50w panels. That is a no go, I think I will sell the 3 50w panels, and buy 2 more 80W panels and the MPPT controller...

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Old 17-11-2010, 14:29   #41
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Brian,

On that note, check out Sun Electronics - they have some great prices on panels right now (Turkey Day clearance). I think I saw some 80W panels for $1.40/watt.

Solar Panels 97/W, PV Systems $1.83/W

They're super nice guys, too. Call them if you don't see what you need.

~Aaron
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Old 17-11-2010, 17:24   #42
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You could get 2 small mppt controllers and series wire the 2 different panel systems seperately and not only have system failproof redundancy but get by cheaper than the Outback controller, though it is a great controller, at least the ones I've installed. Try Morningstar for the smaller controller. I have a Morningstar that is a PWM controller that has been troublefree.
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Old 17-11-2010, 18:46   #43
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I'm interested in hearing about the single MPPT controller used with multiple panels of differing wattages.
I have three panels connected in parallel to an Blue Sky MMPT controller. The panels are 1x130W and 2x43W. This array regularly produces it's full rated amperage, if not a little more. So I know that mixing different sized panels works fine with an MMPT controller.

My question is what would happen if I mixed panels of different voltages. My panels operate at 17.8 volts. What would happen if I added a 16.5 volt panel? Would this create problems for the MMPT logic? Or would it create problems with reverse current flow into the panel with the lower voltage?
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Old 18-11-2010, 10:22   #44
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cfarrar,

As I understand it from reading the information provided with the Blue Sky MPPT, if you have multiple panels of differing voltages, the controller will only be able to utilize the voltage up to the maximum of lowest voltage panel. So in your case, adding a 16.5v panel would force the two 17.8v panels signal's to the MPPT to be reduced to 16.5v.

I'm not sure what this means in reality as to how much power you'd lose. But the manual does state to keep panels within .1-.2 volts of one another, so it's probably worth trying to find another panel to add to your series that would operate at the same voltage.

~Aaron
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Old 18-11-2010, 10:37   #45
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Thanks, Blahman, that's very helpful. I certainly don't want to downgrade circuit voltage to 16.5V.

I was considering adding a flexible panel on the bimini, under my boom, but none of them have voltages compatible with my Kyoceras
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