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Old 26-09-2008, 07:52   #1
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MPPT Controllers for solar

Anybody have recommendations for an MPPT controller? Blue Sky, BZ Products, Morningstar, Outback(a little above my price range). Are they all the same, or is their some compelling reason to choose one over another? Someone had suggested Morningstar to me because they are sealed in epoxy. Looking at 2-400 Watts of solar. Thanks
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Old 26-09-2008, 09:15   #2
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For the 5% - 8% increase over a PWM controller, I wonder if the cost is justified?
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Old 26-09-2008, 09:45   #3
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Ouback 60 is the best one on the market. It is digital and has the best specifications.

Blue Sky is a very good product also. It is analog and not quite as efficient as the Outback.

They ARE worth it in the long run, unless you have space for lots of extra batteries and dont mind the weight of them
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Old 26-09-2008, 09:57   #4
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Performance seems to be arguably similar, but some are sealed, others aren't. Each usually has slightly different features, options, capacities. I'd go for features, warranty, and price, once I'd selected the capacity. And if you get it down to two--don't be shy, contact the makers and say "How do you compare this unit to that one?" and see what they have to say about it, too.

A couple have also had (and possibly solved) RFI problems, so you might want to ask outright if their unit may create interference with VHF or SSB aboard and if you can return it if it does.
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Old 26-09-2008, 10:06   #5
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Originally Posted by hellosailor View Post
Each usually has slightly different features, options, capacities. I'd go for features, warranty, and price, once I'd selected the capacity.
I guess part of my question is also 'what features?'. I've already got a link battery monitor, is there any feature that would be usefull other than the increased current into the battery?

The outback is about $600, and some of the others are between $120-200. Is there something about that Outback unit that makes it worth the difference in price? Analog-digital, I understand how that relates to a gauge, but I don't understand the difference as it relates to a MPPT controller. Thanks
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Old 26-09-2008, 10:24   #6
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I'm not familiar with them all but would think that for a 4x price difference, there's got to be a huge difference in capacity to start with. All MPPT controllers are digital, or hybrid if you'd rather call them that. They take the DC from solar panels and "slice it up" into pulse width modulated (PWM) DC, which can then be treated like AC, passed through a transformer and capacitor bank, and massaged into "just enough" voltage at maximum amperage.
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Old 26-09-2008, 10:41   #7
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Originally Posted by Fishspearit View Post
I guess part of my question is also 'what features?'. I've already got a link battery monitor, is there any feature that would be usefull other than the increased current into the battery?

The outback is about $600, and some of the others are between $120-200. Is there something about that Outback unit that makes it worth the difference in price? Analog-digital, I understand how that relates to a gauge, but I don't understand the difference as it relates to a MPPT controller. Thanks
Are you sure the $100 models are MPPT? The prices you've posted seem like the spread between them and PWM controllers. There is a definate difference in performance, but like I said above, I wonder if the price/performance ratio is worth it. I just refitted new batteries and solar controller in June. I opted for the PWM controller and have no regrets.

By the way. I paid $40.00 for mine, but it's limited to 10 amps of charging current (200 watt panel). 25 amps capability went for about $90. It has Boost and Float charges. MPPT controllers have one or two more stages.
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Old 26-09-2008, 11:01   #8
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Are you sure the $100 models are MPPT? The prices you've posted seem like the spread between them and PWM controllers. There is a definate difference in performance, but like I said above, I wonder if the price/performance ratio is worth it. I just refitted new batteries and solar controller in June. I opted for the PWM controller and have no regrets.

By the way. I paid $40.00 for mine, but it's limited to 10 amps of charging current (200 watt panel). 25 amps capability went for about $90. It has Boost and Float charges. MPPT controllers have one or two more stages.
The cheapest MPPT I've found is the BZ, if you scroll down this page BZ Products Charge Controllers they have a MPPT250 25 amp for $139

The outback is 60amps capacity. That's a lot of panels!

Edit:this stuff is confusing, on the page I just linked above, it says
Quote:
Additional features include PWM charge control, battery voltage temperature compensation and a LED battery gauge.
Why would an MPPT controller also have PWM charge control?
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Old 26-09-2008, 11:43   #9
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Rick-
'MPPT controllers have one or two more stages." Not really, really. There is one maker who claims to have "five stage" controllers but IIRC their "fifth" stage is what you and I would call "OFF". OK, that's a stage.<G>
This "business" is new enough that there's a lot of hyperbole being thrown around. Save it up, put it on the rose bushes, it makes them grow real nicely.<G>

Fish-
"Why would an MPPT controller also have PWM charge control?" Because, the output of an MPPT controller is ALWAYS PWM-DC. Every MPPT controller "is" a PWM charger when it is operating.

25 amps for $140...60 amps for $600...Almost the same price "per amp". enough players are getting into the market, that they are getting competitive.
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Old 26-09-2008, 11:56   #10
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The outback is certainly the best but is way high in capacity for most boating needs and you pay for that. It also gies a lot of very fine control to your voltage settings and provies both daily and historical performance feedback so you know what you are putting in and getting out. There are a lot more functions like fan control, auxilliary control, low voltage cutoffs that you can read about in the manual which is on line.

That said...the Bluesky 2000e for a list of half the price certainly does everything most of us would need (assuming a Link type battery monitoring system is installed) and is easier to both install and operate without the manual!
I don't know the BZ system, but from the manual it appears to have no separate settings for bulk and absorbtion statges...only the float voltage is user set.Nor is there an EQ setting. It also makes no mention of marinization. I don't think this one is suitable but maybe some owners have different opinions.
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Old 26-09-2008, 12:51   #11
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"Why would an MPPT controller also have PWM charge control?" Because, the output of an MPPT controller is ALWAYS PWM-DC. Every MPPT controller "is" a PWM charger when it is operating..
They claim MPPT works this way.

If your Panel(s) is spec'd at 20V open circuit voltage at 5 amps (full sun). You've just bought a 100 watt panel (20x5=100w). However, your batteries charge at around 14.5 volts. The current output of the panel doesn't change, and is still 5 amps ... so 14.5 x 5 = 72.5 watts. What just happend to the other 27.5 watts?

MPPT is said to convert the 20x5 (100 watts) to 14.5x7=100 watts. And therefor are a more efficient charge controller as they make full use of the available power from the panel.

Having said that, no one I know has actually seen this much of an improvement. Yes, there is an improvement in efficiency but it's not 27%. I've heard its 5% to 8% in real life.

Are they better controllers...? Definately. Are they worth the money? I thought not and opted for the less expensive controllers. There's a big difference between $39.95 and $200.00

For $39 bucks I have a two stage charge controller. The first stage regulates voltage to the batteries at 14.5 volts and holds it until the batteries are at full charge. The 2nd stage then floats the batteries at 13.7 volts. There's no equalization.

Works great
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Old 26-09-2008, 13:04   #12
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"MPPT is said to convert the 20x5 (100 watts) to 14.5x7=100 watts."
Pass the hyperbole, I didn't get a chance to eat lunch.<G>

More like, MPPT is said to convert the 100 watts input to 95% output, there's about a 5% loss in the MPPT hardware at the best of times. Different vendors spec 94%-97% under different load conditions and voltages, typically.

Now compare a regular charge controller, when your panels are putting out 20v@5A. The regular charge controller will cut that to 14.4V@5A, at best, producing 72 watts, and since regulators in regulator charge controllers also have some loss, let's say 65W is more likely.

So the MPPT controller is proving 94% compared to 65% with a standard regulator, a potential gain of nearly 50% more power from the panels--under certain conditions.

There are also more esoteric effects involved, like PWM charging batteries more efficiently than plain DC does, so they stay cooler and charge faster--a good thing if it is sunny for only half a day, or you need more charge than you can get in one day. And on top of that, at least one manufacturer DOES NOT USE 'STEPS'. They simply push a slightly higher voltage than the battery is at, with maximum amperage. Again, the battery stays cooler and charges faster--because it is not wasting power that the battery cannot use, in the form of excess voltage.

It is interesting to watch the amperage and voltage from an MPPT controller during a "bulk" charge. I couldn't figure out why the voltage was so low--never reaching "bulk" rates. (Called and found out.)

But there's no denying--they're still EXPENSIVE critters. The only question is, whether the expense is justified for any one owner's charging scenario. If anyone ramped up production enough to really cut the costs (say, to $30 like a PC power supply, which is substantially similar in design)...wouldn't we all update to them.
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Old 26-09-2008, 13:08   #13
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So the MPPT controller is proving 94% compared to 65% with a standard regulator, a potential gain of nearly 50% more power from the panels--under certain conditions.
I know what they say. but have you ever measured more current heading into your batteries from the controller, than the panel could output?

Guys I know who have them say yes...but not anywhere near what you are saying.

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Originally Posted by hellosailor View Post
It is interesting to watch the amperage and voltage from an MPPT controller during a "bulk" charge. I couldn't figure out why the voltage was so low--never reaching "bulk" rates. (Called and found out.)
What did they tell you?

Hyperbole?
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Old 26-09-2008, 13:32   #14
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Rick, last year I ran some tests and set up both volt and amp meters on the output of the solar (input of the MPPT) and the output of the MPPT. I didn't see numbers that high since the panels weren't putting out that much excess voltage. But yes, I did see the MPPT putting out more amperage than was going into it.

I wasn't claiming those numbers--just using your numbers, based on a panel supplying 20V as you cited.

Panel outputs can be funny too. In low light, you may measure 16V from a solar panel, but if oyu put it under load, that can drop to 9 volts. No effective output power--even with an MPPT--even though there is voltage. The MPPT really shines at taking both 'marginal' and 'excess' power and making it useful. I suppose you'd have to A/B it against conventional controllers to get real numbers, but I'd suspect it buys you an extra 10-15% in real power over the course of a real day, with typical battery cycling.

What "they" told me was that the microprocessor in the their MPPT controller is being put to good use. You program it with the battery capacity and the charge voltages appropriate to the battery type (or specifically from the maker) and it continually monitors voltage and amperage and continually adjusts both. You could call it a "512 step" controller instead of a 3-step controller. (Maybe 128, maybe 512...they don't talk about the program details in the computer.)

I ran this against a lead engineer from a major battery company, and he confirmed that no one wants to talk about the trade secrets--but as battery makers, they were certain this was the better way to charge batteries, and they had confirmed it. How much better? Well...trade secrets again, and mixed into the fact that PWM was a better way to charge, but he was sold on it.
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Old 26-09-2008, 13:37   #15
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I have a Blue Sky 2000E and had it for about a year.
I saw a big difference after adding the gizmo, it was like a adding a third solar panel, no bull.

I got the MPPT for free so I don't really have dog in the fight, or trying to justify the purchase by wishful thinking regarding the output.

Knowing what I know now, I would have bought one years ago when they first came out...Snake-oil it is not.
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