How to choose MPPT size

[jseas]

Basically you just need to know the max amps your panels deliver, then buy an mppt charger that allows for what you need. If you are pushing 40 amps then buy a 45 amp charger. Use ohms law...Watts divided by Volts = Amps. But really you should eliminate the odd panels and verify your wiring.

[Canibul]

Well, I have some numbers. I unbolted the panels and took photos of the labels. I hope this is enough info.

1. The small panels with the blue corners are these, and I have two of them:


2.) The square panels with the dark gray color are these, and I have four of these:


3.) and now for some bad news, for me anyhow. I still have a panel to match the large one with the blue cells in the lower left hand corner of that photo. It was still in the carton it was shipped in. I opened it this afternoon to get the numbers off of it, and find that sometimes in the past year and a half since we left Jax with it on the boat, a hole has been punched all the way through it. Through the box, and through one of the solar cells. Since a little shade screws these up, I am assuming a hole the size of a screwdriver tip makes the whole thing useless. Anyhow, I still have ONE of these, plus the one with the hole in it:


Is that enough info for me to start making a shopping list?

[Canibul]

Guess not.

[cheoah]

Originally Posted by Canibul

Guess not.

Canibul, I'm not the expert with lots of solar installs under my belt. I'll give you my opinion though. I bought Kyocera panels for my boat, and genasun gv-10 MPPT controllers. They are not cheap, but they are very high quality and great performance. There is some benefit to having an individual controller for each 120-140 W panel. It avoids the mixing issue with different V or I. It avoids the issue of loss of performance of part of the array is shaded. You really have too many panels to do that, but breaking them into groups of like panels and buying a controller for each group is one option. I can't reference your exact list of panels on this iPhone, but the first two groups might go parallel to one of the other brands of that accommodate higher output and is more cost effective.

The single panel with the broken mate could go to a genasun - or a cheapie, but you may find enough increase in performance that an MPPT like genasun's makes sense. I think you could easily sell it if you did not see enough increase, and even compare with a basic morningstar non MPPT and see what your battery monitor says. Might hook the broken one up for laughs and just see what the output is.

Do you have a bus bar setup near your batteries? Your controllers can be mounted at the end of the wires from the panels, with properly sized wire to a common bus bar. All of your charging sources can terminate there with one cable leading to your bank.

Sure enough, look at the blue sea, Morningstar, genasun, and solar power sites and compare controllers. I think whatever MPPT you get will be pricey, and it's debatable whether it is worth the investment with that group of panels. Personally I would really want to compare on the battery monitor, and easy enough to wire one for a few sunny days, then the other.

As far as the high voltage panels requiring an MPPT, I wasn't aware of that. I understand that they take advantage of high voltage, but I thought that other types of controllers could regulate them too. There is no doubt some clever way to do this without breaking the bank. Hopefully someone with a larger mixed array, or even a menagerie like yours will chime in.

Good luck with your project.

http://genasun.com/all-products/sola...ge-controller/

[susswein]

My recommendation:

Wire the 2 ICP panels together in parallel. This'll give you 8 amps at at 12V (nominal).
Wire the above in series with the synergy panel. This'll give ~7.5 amps at 24V.
Wire this in series with the 2 guangyi panels to give you ~21 amps at 24 volts.

You'll need an MPPT controller that rated for 25 amps and can accept an input voltage of up to 30 (Vmax).

If you search for MPPT on youtube you'll see some test of chinese made MPPT controllers in this capacity range for under $150 that work well (along with some that don't).

[noelex 77]

The 2x ICP and the one solar cynergi panel can be wired together in parrallel.
The difference in the Vmp (16.2 and 17.6v) means there is little point going for a MPPT regulator and in fact a cheap one will probably mistrack badly with this set up so use a Non MPPT PWM regulator.

The Cuangti panels will need a separate regulator and is has to be MPPT. Wire these up in series or parallel or a combination of both depending on your religion.
My recommendation would be parallel if the wire size is adequate.

The good news is that you have loads of watts.

The bad news is the MPPT controller for the 4 x 120w panels will be expensive. With this sort of wattage Outback and Midnite are the best controllers if the budget will stretch.

[Canibul]

Thanks for the good news. I was thinking I would have to buy another Cynergy panel, and the shipping costs would eat me alive.

I still have a Morningstar ProStar 15 controller that I think survived the lightning. At least it doesn't look fried. The MPPTs were definitely toast. I'm talking smoke and fire. Is that of any use here? I suppose 15 amp controller was most likely hooked up with the six Harbor Freight panels that I am going to junk.

And the budget is okay. I don't mind spending a few bucks for quality. In fact, I wish I had the opportunity to choose quality in other purchases. So often these days it's the cheapest tool at premium prices. (Anyone remember when Craftsman was a mark of quality?)

So any firm recommendations for the best model controllers for this setup?

And thanks for the help. It's very much appreciated.

[zeehag]

i usually used a size larger than i needed,,,amps in , amps out.
my ericson had max in capability of 20 amps. i got a 25amp controller. that way i could add without problem.
my formosa which i am cruising currently uses a 20 amp pwm controller. i have another 25 amp pwm controller spare. is usually enough for my needs so far. right now i am seeing input of only 1-6 amps hourly charging my batteries. .

[Boracay]

If yous do a search in ebay on "30A" solar controller you should come up with a selection.

Mine seems to be fairly common under a few aliases. I've been putting up to 20A through it for a few years and it still looks healthy though the experience of others may vary.

From memory the wire cost more than the controller.

Not an MPPT though. Does seem to be PWM.

[Canibul]

Thanks. We don't do ebay, but it gives me ideas on what to look for.

[jseas]

I would stick to name brands unless you are carrying a spare. Morningstar, Blue Sky, or Outback. The Morningstar Tristar mppt 45 or 60 is widely used on cruising boats in the tropics. It has epoxy encapsulated components unlike the chargers from china.

[Canibul]

any downside to using the larger one, other than initial purchase price?

[jseas]

No downside. Buy as large as you can afford. Solar prices continue to fall so you may find yourself with abundant amperage in the future.

[noelex 77]

Originally Posted by Canibul

any downside to using the larger one, other than initial purchase price?

Generally no, but the self consumption does go up as the tracking ability and the maximum current acceptance increases.
With a sophisticated high power solar controller (like the Outback) the self consumption can exceeded the improvement in power extraction, if it is matched with a small solar array.

With a smaller solar array the outback would be a poor choice because the gain from better MPPT tracking would be lost driving the complicated processing power necessary for this better tracking. The cut off point is debatable, but for the Outback it is about 200w, below this level a Rogue or Genasun controller would be better.

[Canibul]

So, I got two 65's and a 120 watt for a total of 250 watts on one controller, which can be some quality PWM for more than 16 amps, and four times 120 for a total of 480 watts on the other controller, which needs to be a high end MPPT that can handle something greater than 20 amps. Correct?