What Type of Controller(s) Should I use for these Solar Panels?

[ErikFinn]

I would need some help with my solar panel set up please. In particular the controllers.

I searched and read a couple dozen threads but couldn’t find answers to my questions.
The setup is old, about 10 years, and it came with the boat when I bought it 1,5 years ago. I suspect the controllers have gone bad as they appear to cook my batteries (4 x Trojan 105, which I will replace also), and therefore I would like to replace the controllers but would appreciate advice from the CF knowledgeable folks.
Setup consists of 8 panels, 85W each. I attach a photo of the product label with specs. The second photo is the current controller (there are two, installed is series as per the manual; which I couldn't find now to check the exact wording) As far as I understand the 8 panels are set up so that there are two groups of four panels in series.

I would like to know:


1) What type of controllers should I use for these panels?


What I think I have understood reading the CF threads is that MPPT controllers would not be best for my lowish wattage panels? MPPT controllers are better suited for panels about 130W & up? Is this correct?
For my set up I should look for a PWM controller? What amperage should I get?


And would it be best to install two, one for each group of four panels?


Also the cost is a concern and I will not consider an $800 or $1000 controller (or two) for this boat. If a PWM is recommended, would I be able to get a fairly good one from say eBay for say around $50 each ?


What should I look for in a good controller? Would equalizing function be desirable for example?

Thanks,
Erik

[noelex 77]

The first question is are you sure the controllers are bad? They are quite easy to test. It is certainly possible you have a bad battery or two this can result in gassing even if the controller is doing its job.

With 680w in total you will need a high capacity controller around 60A and reasonably quality models that will handle this current are expensive. The cheap ebay models are not very good.

You can use a MPPT or a non MPPT (PWM) with your panels, but if you do the latter they will need to re-wired to parallel and probably thicker wire as well.

The best bet for a controller in your price bracket (assuming they are bad) would to be find one second hand. There are a few PWM on the market for reasonable prices from people that are upgrading to MPPT, but given the possible cost of upgrading your wiring they will need to be cheap. (Are you sure the panels are in series? Given the age of the controller I would expect it to be a PWM model, which means they must be wired in parallel.)

Try looking at a second hand Plasmatronics 60 A model ( or two of the 40A models) (both are very good) or something similar from Morningstar.

[djmarchand]

The cheapest name brand PWM controllers are probably Morningstar. I think I would set up two controllers, one each for 4 panels wired in parallel to the controller. The Imp is about 5 amps (which will probably be the same at the lower battery charging voltage of 13-14 V), so the total output of each bank is about 20 amps. You will need a 25 amp controller at a minimum. Morningstar makes a 30 amp PWM controller for about $100 each.

You should also use 10 gauge wire minimum (8 is better) from the panels to the controller and the same to the batteries- with a 30 amp fuse at the battery end.

[ErikFinn]

Originally Posted by noelex 77

The first question is are you sure the controllers are bad? They are quite easy to test. It is certainly possible you have a bad battery or two this can result in gassing even if the controller is doing its job.

Thanks Noelex for your always professional and courteous reply.
No, I'm not sure the controllers are bad. But definitely one of my domestic batteries is bad, and rather than replacing one battery I need to replace all of them, as recommended (not combining old & new batteries in a bank).
So, the T105 batteries are nearly USD200 each here in Malaysia from a distributor. that makes it about USD800 for me to replace the four batteries. I was hoping to replace the controller(s) with no more than USD200 spent, that would be acceptable.
At best I can see about 10Amp from the panels on the ammeter so I believe this is not good enough. I'm hoping to improve this and eliminate any possible fault on the now very old controllers.

Originally Posted by noelex 77

With 680w in total you will need a high capacity controller around 60A and reasonably quality models that will handle this current are expensive. The cheap ebay models are not very good.

Whats the formula for calculating the Amperage for the controller? Which values I have to look at on the product sticker? I'd like to know the math behind the requirement please so I can understand the situation better..
And if I divide the 8 panels to 2 banks and use a designated controller for each bank I can then use a controller of half Amperage for each bank?

I'm not looking for something top range (like Morningstar or Outback I believe have been quoted) but rather I would prefer something that is ok, not the cheapest, but ok quality... Maybe even buy 2 spares as we have a lot of thunderstorms in here and a lightning strike is always a possibility..

Regarding the eBay models, if I go with something mid range U reckon it would do the job? Something ok here: ?

solar panel regulator | eBay

Originally Posted by noelex 77

You can use a MPPT or a non MPPT (PWM) with your panels, but if you do the latter they will need to re-wired to parallel and probably thicker wire as well. The best bet for a controller in your price bracket (assuming they are bad) would to be find one second hand. There are a few PWM on the market for reasonable prices from people that are upgrading to MPPT, but given the possible cost of upgrading your wiring they will need to be cheap.

Would you have a link or something to explain this PWM parallel rewiring? Any ballpark estimate for the cost of rewiring? (cos maybe if high, then I should take a closer look at MPPT controllers I guess... As I was under the presumption I could just swap in any type controller of my choice without altering the rest...

Originally Posted by noelex 77

(Are you sure the panels are in series? Given the age of the controller I would expect it to be a PWM model, which means they must be wired in parallel.)

Actually I am not sure. The black boxes glued underneath each panel are hidden from view and I haven't taken a closer look inside the boxes to see the actual connections there.
However, in a bank of 4 panels, each panel appears to be connected to the next one by a single wire, and from the last panel of the bank there are two wires going into the controller.
The setup was was installed by the previous owner who is no longer with us.

Originally Posted by noelex 77

Try looking at a second hand Plasmatronics 60 A model ( or two of the 40A models) (both are very good) or something similar from Morningstar.

Will do thank you, are these MPPT?
Thanks and best regards,
Erik

[ErikFinn]

Originally Posted by djmarchand

The cheapest name brand PWM controllers are probably Morningstar. I think I would set up two controllers, one each for 4 panels wired in parallel to the controller. The Imp is about 5 amps (which will probably be the same at the lower battery charging voltage of 13-14 V), so the total output of each bank is about 20 amps. You will need a 25 amp controller at a minimum. Morningstar makes a 30 amp PWM controller for about $100 each.

You should also use 10 gauge wire minimum (8 is better) from the panels to the controller and the same to the batteries- with a 30 amp fuse at the battery end.

Thank you djmarchand for your kind post.

One thing (among others, lol) I'm still unclear about is which type controller is better for these panels, MPPT or PWM?

As you say setting up two banks with designated controllers on each bank, (port and starboard) I feel might be a good solution as the banks are at different angles so maybe a god reason to have designated controllers as well. Also I have occasional shading from two backstays and antennas.

So a 30 Amp controller for each bank should be sufficient? Anything bigger than 30 Amp would be waste?

$100 each certainly doesnt sound bad, way better than $800 to $1000 for a MPPT...

What would be the equal measure for 8 gauge wire in millimeters? In case the local shop don't speak "gauges"..? And honestly I'm unfamiliar also...

[djmarchand]

Eric:

Yes, anything bigger than 30 amps with 4 of your panels attached would be wasted. You do want a safety factor above the rated output of the panels so 30 amps gives you a 50% safety factor, which is plenty. A 25 amp panel would also work, but Morningstar doesn't make one.

The cheapest Morningstar controller I could find online is about US$130 each. You can buy cheaper Chinese controllers, but......

An MPPT controller can improve overall output to the batteries by about 10%. But as you note the price difference is substantial.

8 AWG (American wire gauge) is 3.3 mm diameter and 8.3 mm2 cross sectional area. Use the closest that you can get locally.

David

[noelex 77]

Originally Posted by ErikFinn

At best I can see about 10Amp from the panels on the ammeter so I believe this is not good enough. I'm hoping to improve this and eliminate any possible fault on the now very old controllers.

A maximum of 10 A from your set up is poor, but its more likely that the fault lies with the batteries not accepting charge, or that there is some other fault such as poor connection. Reduced current is not not a common failure mode for controllers (although not impossible)
Providing you monitor the battery voltages and these stay within acceptable levels your controllers will not damage new batteries. The solar panels can be disconnected if the voltages become unacceptable.

Originally Posted by ErikFinn

Whats the formula for calculating the Amperage for the controller? Which values I have to look at on the product sticker? I'd like to know the math behind the requirement please so I can understand the situation better..

The maximum current you will see from each panel with a PWM controller will be slightly above the Imp and less than the Isc.
For a MPPT regulator you are better looking at the wattage of the panel and dividing this by the lowest battery voltage you are likely to see (dividing by 12 is reasonably safe). There is some losses in the voltage conversion, but panels can occasionally put out more than their specifications.
So with 8x85w/12 we have 56.7A.
Most (not all) regulators will self protect themselves if you exceed their peak current capability, but it better to have a little reserve. The closest step is a single 60A regulator. (Regulators can be rated at anything but 5,10,20,30,40,60 and 150A are the most common options produced)

Originally Posted by ErikFinn

And if I divide the 8 panels to 2 banks and use a designated controller for each bank I can then use a controller of half Amperage for each bank?

Yes you can have 2x 30A regulators

Originally Posted by ErikFinn

Regarding the eBay models, if I go with something mid range U reckon it would do the job? Something ok here: ?

I will take a look

Originally Posted by ErikFinn

Would you have a link or something to explain this PWM parallel rewiring?

With MPPT regulators the panels can be wired in series, or parallel. Series increases the voltage, but reduces the current when compared to the parallel option. As wire size is dictated by current the wire from the controller to the panels can be made thinner if the panels are wired in series. The MPPT regulator performs a voltage conversion to convert this back to a suitable voltage for your batteries.
A non MPPT regulator (often called a PWM regulator) cannot perform this voltage conversion so the panels must be wired in parallel.
I think it much more likely your regulators are not MPPT and therefore have to wired in parallel (unless someone has stuffed up which would also explain the poor output). So presumably they used large wire appropriate for the higher current. You should redo these calculations anyway (let me know the total distance of wire from the panels to the controller and then the controller to the batteries And I can do the calcs for you) Wiring that is too thin will reduce the output (although not enough to explain only 10A from your array)

Originally Posted by ErikFinn

However, in a bank of 4 panels, each panel appears to be connected to the next one by a single wire

That does sound like series.

Originally Posted by ErikFinn

Will do thank you, are these MPPT?

No. An MPPT regulator would be best for your panels and give a slightly higher output than a PWM regulator, but MPPT regulators are complex and expensive. Cheap MPPT regulators do not work well or last. Therefore if you are trying to reduce the cost of the regulator a PWM model is the better choice. If cost was no object I would go with a MPPT regulator, but buy a good one.

I think the first step is to sort out what is happening with your existing wiring. If the controllers are MPPT controllers and the wiring is in series if you want to keep the existing wiring the controller must be MPPT it must also be rated for the maximum voltage

[noelex 77]

Originally Posted by ErikFinn

Regarding the eBay models, if I go with something mid range U reckon it would do the job? Something ok here: ?

solar panel regulator | eBay

The link only leads to all the solar regulators on ebay. Did you have any particular one in mind?

I am not a great fan of the numerous no name regulators on ebay. They seem to have a short life with poor performance.

[BOATDOCTOR]

WAY too busy to READ everyone's posts but from what I scanned these guys are steering yoi in the right direction. Sorry to sound condescending folks but I am one of the most recommended techs in the Caribbean on this stuff.

My short answer is don't skimp. If you're out here seriously, you don't want power problems, wasted batteries, etc. IF you can afford it, get yourself an Outback Flex 60, and leave all your worries to it. It is VERY smart, and extremely stout. I beat the crap out of mine by having it installed in one of the engine rooms and continuously forget to shut it down when motoring. Thus, it gets "cooked" while under way, yet still does it's job of monitoring everything, and knowing not to add power to the mix that isn't needed. Reason to shut it own is only to protect it from overtemping - it's designed to stay online in all conditions, engines running or not.

Here isca link to the best source I recommend:Charge controllers on sale, charge controllers by Schneider Electric, Trace, Outback Power, Solar Boost, MorningStar, Prostar, Sunsaver, Sun Guard and more!

$500 on their site right now. Connect the panels in series for more efficiency - it handles high voltage. Might double check the math adding up your particular panels and compare to the unit. Guys who work for WS will help too.

The unit is not only capable of maintaining batteries in top condition, but it can also "condition" not completely wasted batteries back into decent shape. Sorry no time to offer more here...

[socaldmax]

You've gotten some good advice so far, especially from noelex.

Here's what I would do if I were you.

1. Replace the batteries. Start doing some hard core searching for a wholesale source for golf cart batteries. Call around to the golf courses, etc and find out where to get 6v GC batteries for cheap. Some people swear by Trojan or whatever brand name they swear to. There are only about 4 major battery mfrs. and everyone else slaps their label on it, so paying 2x or 3x for a name is a huge waste of money. I get 6 yrs out of a set of $80 "Kirkland" brand, sold by Costco and made by Johnson Controls. Do an internet search for all of the brands JC mfrs for to get an idea how widespread they are.

2. Check the input and output (V and A) of each controller, disconnect the other one if you think you're getting screwy readings. Even if the panels are fairly old, they should still put out virtually full capacity, anything less indicates corroded terminals or bad (or too small) cabling.

3. If the panels and controllers check out, you're all set.

If the controllers aren't putting out any power, see if you can find a good quality used controller for cheap locally. If not, there is one cheap MPPT controller online that I've had excellent results and performance with. It's called eco-worthy and it's a 20 A MPPT controller with an excellent LCD display for $102 delivered. You'll need 2 of them. A couple of spares might be a good idea at that price. If you connect 2 panels in series then connect 2 pairs in parallel, you'll be putting in 11A at about 34V to each controller, which should put out about 20A @ about 14 or 15v (I have mine set for 15V for better charging.) The controller is fully adjustable in .1V increments for bulk, absorption and float charge V. With 340W input to each controller you should be getting at least 17-18A, possibly 20-21A output under perfect conditions per controller. I have 410w going into one and it's topping out at 22A by 10AM. 410w would be better off going into a 30A controller (with probably 24 or 25A out), but the price difference is pretty big, so 22A is good enough.

[ErikFinn]

Thanks for all the very helpful posts friends. Just a quick update about my current controllers (Trace Engineering C30A+ as per the foto on my first post); I spent about an hour searching the internet and found that apparently Trace was acquired by Xantrex, and Xantrex was acquired by Schneider Electric years back, and that there is a fair chance my controllers may be closer to 20 years old as opposed to 10...
I found a forum where they talk about "Trace C30A" (not my "C30A+"), and there was a comment dated 2007:

"The C30A was an old relay type controller that was discontinued by Xantrex/Trace about 5 years ago."

trace c30a

So if this is the same controller as mine its pretty old now, lol, and if it is a "relay type controller" then I suppose its fair to say its not even a PWM nor a MPPT...

So my thoughts now are to check the wiring for connection issues, measure the wire thicknesses. I suppose it would be prudent to measure the output of each individual panel also from the black boxes under the panels. Then decide on the new controller(s).

If the panels are ok I trust I should be able to improve the total amperage of the setup going through these steps?

[socaldmax]

You should be able to.

Shading is a big deal, even a little bit of shading over one panel will result in a large loss in power. Do whatever you can to minimize it.

[ErikFinn]

I'd have a few more questions to help me understand more about this solar puzzle.. Hopefully the discussion offers some knowledge to the forum as well.

I have not decided yet if I should get a PWM controller(s) or a MPPT controller. A neighbor in the marina said that here in the tropics you really dont get an advantage using MPPT, that it gets better in lower light conditions, such as in arctic conditions. Is there any truth to this? Would I be just wasting money getting MPPT here in the tropics? I have read just about every thread but it is difficult to make these decisions not being a professional.

I gave up on looking at eBay for cheap China ones, better get good quality ones I concluded. If I want to get this system work and get a long service life out of my new expensive batteries.

Found something like this made in China, price is in AUD, but for two units it becomes quite close to 400, which is not far from the price of the better units NOT made in China,so why take the risk? I discarded this option. (But these apparently sell like hot cakes in Australia, many shops were out of stock.)

I found out that the distance from the controller to the batteries must be short, the physical wire run length. "In no case should it be even six feet away", said HandyBob. So this means that I cannot install the controller(s) in to the the nav station area (which was my original desire), because its just too far from the batteries. Well, that means that I also then need remote display(s) to see whats going on. As the actual controllers will have to be installed in to some "funny" spot close to the batteries but where they are not readily available.

Here is a brief list of what I've looked at so far (prices from wholesalesolar linked on one of the above posts):

MPPT controllers:

-Rogue MPT-3048; 30 Amp MPPT, seems very good quality, price is about USD 350 plus about USD 100 for the standalone display and interface, so about USD 900 total for two. Ouch.

-OutBack FlexMax 80, 80 Amp MPPT, about USD 520, plus remote display ("MATE") about USD 210. A total of about USD 730. I could also add a "FLEXnet DC" (about USD 270) which would do away with my need to buy a battery monitor (which I do not have now, but want to get; I'm considering the Balmar SmartGauge for about USD 300).

-Midnite Classic 150 MPPT about USD 600. Looks like a 96 Amp model (so more Amps than the others), and also the display can be relocated, so no need to buy an additional remote display, which is nice.

-Morningstar TriStar MPPT TS-60 about USD 500 plus remote display about USD 110, so total USD 610.


PWM controllers:

Morningstar TriStar-60 PWM controller about USD 190 plus remote display USD 110, total USD 300.

Morningstar ProStar PS-30M PWM , about USD 170, so 340 for two. Looks like no remote display is available.


The PWMs are cheaper, so if it makes sense, I have considered it might be a good idea to get one 30 Amp controller for each bank of 4 panels. (because the two banks are at different angles towards the sun, please look at the attached foto).
For PWM the panels must be wired in parallel, not series.
What do you think? One or two controllers?


If an MPPT is definitely a superior choice, would a single 60Amp (or higher) MPPT controller for all the 8 panels work for my setup?
Again, arrange the 8 panels to two banks of 4 panels (4 panels in series, as MPPT enables this), and connect the 2 banks to a single 60 Amp MPPT controller?
Are the connectors in the controller big enough to make so many connections?
Would a single MPPT controller be able and smart enough to handle this kind of setup?
Or would it all go horribly wrong when the single controller receives different charges from the two separate banks of panels?
Would a designated MPPT controller (30Amp) for each bank of 4 panels be a much better setup, than just a single 60 Amp MPPT controller for the two banks?
Or is just the same, no difference whatsoever?

Thanks and best regards,
Erik

PS. I do not want Schneider (Xantrex) cos they are made in China now, or Blue Sky cos having read a few things makes me believe the other brands are better. I might be wrong of course.

PPS. my panels are size about 53 cm x 120 cm (about 21 inch x 47 inch); anyone knows if these can be bought anymore anywhere (similar) if I need to replace panels (photo at first post)??

[socaldmax]

Assuming that the 2 sets of panels are always producing a different voltage due to their different orientation, I don't believe there is any single MPPT controller that can accurately set the MPPT for 2 different voltages on a single line.

It would be better to go with 2 x 30A controllers for better tracking. Since you plan on connecting the panels in serial, MPPT is the only answer, despite PWM being much cheaper.

In regards to MPPT controllers price vs quality - there isn't a strict correlation. More expensive isn't necessarily better. It could be just higher mfg costs, greed, poor cost control, or a combination. Some of the less expensive controllers are made in China, do a great job, last a long time, are well built and just don't cost a lot to build. Labor is a major expense in the US, a fraction of the price in China. The quality of the components is a major factor, but most components are made in China to begin with, so if they spec. good or better components, they're getting them cheaper at the source.

Having said that, you might be interested in the Midnite Solar Kid 150 MPPT. Made in the US, great rep., sells on Ebay for $319. Might be cheaper elsewhere, espcially if you buy 2.

As far as HandyBob goes, he's a wealth of info, but sometimes I think he goes a bit too far, like the less than 6' thing. If you replaced all of your existing cabling with 6 AWG or 4, you'll be fine over longer distances, especially if you have all 4 panels in series, or have them in series pairs. The Midnite solar can take up to 150v, so it should do 4 panels in series no problem.

You can be creative with the cables, too. I ran 6 AWG cables from my solar panels to my controller, and 6AWG from my solar controller to my 75A battery charger, about 6 ft away. I spliced the cables in with the 4AWG cables going from the 75A charger to the batteries, instead of a separate set of cables. I don't run the charger during the day, so the same cables carry solar power during the day, and occasionally 110v charger power at night.

[noelex 77]

The advantage of MPPT over a non MPPT regulator (PWM) is not great and the advantage gets less at hot temperatures as your friend pointed out. There is some dispute over the actual power gain, but around 10% might be a reasonable number.


Non MPPT regulators do not do not do any tracking so there is no advantage in multiple controllers for panels in different conditions. A separate controller for each panel will not produce more power with a non MPPT controller.

A single large MPPT controller like an outback 60 is an OK solution. The flexnet DC option works well as battery monitor and the combination provides for better regulation with termination of the absorption phase based on battery return amps rather than a simple timer. The Flexnet DC does have a slight software problem where the battery monitor zeros itself slightly early in some circumstances, it is annoying rather than any great practical significance. Overall it might be the best solution for you.

The controller can be placed anywhere, but the longer the run the thicker the cables need to be. The cost and the difficultly installing thick cables means the distance are better kept as short as possible, but there is no difference in performance with greater distances providing the wire is sized accordingly.
With An MPPT controller wired in series the required wire sizes will be smaller if the controller is situated close to the batteries. With a controller wired in parallel (MPPT, or non MPPT) it does not make much difference.