Solar Panel hookup

[ClassC.RV.470]

[font=Verdana, Arial]Ok, this is my dilemma. I have 2 Renogy 100 watt panels hooked up in parallel into my Rover 40A charge controller. I was given a 275 watt panel that I want to add to it. What I was thinking was hooking up the 2-100w panels together in series then adding the 275w panel with them in parallel. The two 100w panels are rated 18.9 Vmpp, 22.5 Voc, 5.75a Isc each, when doubled it comes out close to what the 275w panel is, which it’s spec.s are 31.0 Vmpp, 39.4 Vic, 9.58a Isc. Now would this work out Ok, be my best way of doing or would I be better off just tying them all together in parallel instead of the series/parallel route? What can I expect from all this, it’s hard to pass up a 275w panel. The [/font]

 

[John61CT]

Get a separate controller for the. unmatched panel.

Victron MPPT 75/15 is excellent value ~$100

Being limited to ~220W **output** will only be an issue in rare peak conditions, overall you will get much higher output than going with a cheaper 20A controller.

Paying $200+ to get good quality and higher capacity is IMO not worth the marginal extra output.

 

[tx2sturgis]

As above, the panels are mismatched so you need a separate controller.

You could add another battery bank just for that controller and panel, or tie the controller into the same battery that the other panels are charging, with the understanding that the controllers could end up with slightly different voltages and settings. 

Another option is to trade or sell that odd panel and then buy another matching panel or two.

 

[ClassC.RV.470]

Thanks for the quick reply to my post. I was thinking about using a separate charge controller also because of the difference in voltage’s and amperage but was hoping to use just the Rover 40A controller. I do have a new 30A Wanderer controller that came with the 2-100w panels so I guess I’ll use it for them and hookup the 275w panel to the Rover. Think there’s any problems with hooking them both up the the same 2 deep cycle batteries I’m using now? BTW I am planning on up grading those batteries to 2-12v 200ah AGM batteries at the end of the month. Thanks again, you guys are great,

 

[John61CT]

No, paralleling multiple charge sources to one bank NP.

Best to match setpoints, charge profiles but NBD.

​The best battery value by far is Duracell (actually Deka/East Penn) deep cycle golf cart batteries, 2x6V, 200+AH @ less than $180 from BatteriesPlus or Sam's Club.

Two pairs of those will be much better value than whatever you were considering.

Unless you really **need** AGM

 

[frater secessus]

[rearranging the quotes on purpose -- frater]

I do have a new 30A Wanderer controller that came with the 2-100w panels so I guess I’ll use it for them and hookup the 275w panel to the Rover. Think there’s any problems with hooking them both up the the same 2 deep cycle batteries I’m using now? BTW I am planning on up grading those batteries to 2-12v 200ah AGM batteries at the end of the month.

Wanderer on the paralleled 2x100w panels is a great (and free!) solution. Multiple chargers on the same bank are fine; as John says keep the setpoints aligned. Bonus: you get better shade handling with separate controllers.

I don't consider AGM an upgrade from FLA deep cycle, particularly in solar-charging-only installs. I'd ride the existing batts until they fell over dead.

Thanks for the quick reply to my post. I was thinking about using a separate charge controller also because of the difference in voltage’s and amperage but was hoping to use just the Rover 40A controller.

The two-controller option above is best, I suspect. BUT.... here are further thoughts on the combined approach.

The Vmp on the big panel is low enough that it looks like a 60-cell unit to me.  If it was 72-cell then the serially-combined 100w panels' Vmp would be close enough to make the series-parallel config interesting enough to test.

Running them all in series may give the least bad of the single-controller configuations and would be easy to cable up and test.  The Rover will take up to 100v input so you have plenty of room there.

Here is a relevant video from AltE;  I love the demos she does!

 

[ClassC.RV.470]

Thanks for the additional option, running them all in series,which is what I’m looking for even though I have an extra charge controller to use if needed, less wiring and holes in the RV. And yes it is a 60 cell panel and being new to this solar stuff, I don’t know why a 72 cell panel would be a better series/parallel combination option?? I’m just trying to get the best results out of what I have available. I’m going to see what I come up with running all the panels together in series before resorting to using separate charge controller’s but one thing I don’t understand is the set point alignment part. Any and all information is greatly appreciated, hopefully everything I learn may help someone else attempting the same thing. Thanks much.

 

[tx2sturgis]

Running them all in series may give the least bad of the single-controller configuations and would be easy to cable up and test.  The Rover  will take up to 100v input so you have plenty of room there.

Frater, the combined voltage of those 3 panels in series does add up to less than 100 volts, BUT...

Won't the entire array in series be limited by the amperage that the two 100 panels can make? (effectively the same as hooking 3 100w panels in series)

Sort've like hooking a 6v 100 ah battery in series with a 6v 200 ah battery. 

I've never hooked up 3 mismatched panels in series so I can't say one way or another. 

OTOH, it may be enough surplus power than a few amps won't make a difference. 


Hmmm....

 

[frater secessus]

Less wiring, yes, but same amount of holes in the roof. If you parallel you'd combine the wires before bringing them through the roof.

And yes it is a 60 cell panel and being new to this solar stuff, I don’t know why a 72 cell panel would be a better series/parallel combination option?? I’m just trying to get the best results out of what I have available.

72 would be a *better* series+parallel option, but still not a good one. Less bad. The Vmp of the 72 would happen be closer to the Vmp of the serialized 100w panels. This would allow them to be less hamstrung in the configuration.

Flipside: If the 100w were poly their combined Vmp would be closer to the Vmp of the 60cell.

So maybe something like 350w if the Vmps were more matched and 325w if less matched. Still not as good as separate controllers, which might yield a max of 425w if the 2nd controller was the PWM.

 

[frater secessus]

Frater, the combined voltage of those 3 panels in series does add up to less than 100 volts, BUT...

Won't the entire array in series be limited by the amperage that the two 100 panels can make? (effectively the same as hooking 3 100w panels in series)

There is a gain over 3x100 (as in the AltE tests) but not much.  I agree that separate controllers are a much better solution.

 

[jimindenver]

A 275 watt panel is going to peak at close to 20 amps mid day. I would certainly go with a 20 amp MPPT controller and NOT lose that excess amps. A Eco-Worthy 20 Amp MPPT controller is simple to set, simple to wire and will blow a 15 amp controller away. Same price, just more power. Side by side with a top of the line MorningStar MPPT controller it matched the output every step of the way. Changing the settings takes just seconds and a few pushes of a button instead of needing a dongle, remote panel or computer to be hooked up. I gave my first one away after using it for 5 years, well built as long as you don't intentionally overload it.

The other thing is I do not agree with over paneling as it stresses the controller. They say it doesn't but there have been post here to the contrary and with a controller from the company that first said it was okay. The excess power comes out as heat and heat is the bane of electronics. Until Morningstar decided it was okay to do so we went with a 20% buffer to make sure we didn't fry our expensive toys.

You really shouldn't combine them all together or even run the two in series and parallel it with the larger panel because A it will reduce the ability of the controller to find the sweet spot in voltage and B the lower panels voltage will hamper the highers voltage in series.

So separate the systems, match up the settings and go forth with as much power as possible.

Think of combining panels like water hoses. The smallest hose rules the roast. No more water will pass through the two hoses than will go through the smaller hose so no matter how big the bigger hose is, it is restricted to the smaller hoses flow. Two panels with differing voltage will act the same way as well as confuse the controllers ability to track the power point.

 

[ClassC.RV.470]

Thank you all. I love it when great minds come together, it gives me a vast amount of information and will save me unnecessary time and trouble.

 

[ClassC.RV.470]

This is starting to confuse me and I need to focus on the equipment I have on hand. I have a Rover 40A and a Wanderer 30A charge controller that I’d like to hookup the two 100w and one  275w solar panels to and try to achieve the best possible results from it all. As far as my posts go, just like Solar, I’m new to this also. But I truly appreciate any and all suggestions. Thank you All

 

[John61CT]

One controller goes on the matching pair.

The other takes the big one.

Simple enough?

If you want to test, see which configuration gives greater total output, put them on a depleted bank and measure amps output as you add variable loads

 

[tx2sturgis]

One controller goes on the matching pair.

The other takes the big one.

Simple enough?

John, I just KNEW you had it in you!



Hey Classy, this is THE answer.

 

[ClassC.RV.470]

Thanks guys, you’re the best. Going to put the two mono 100w panels on the Wanderer controller and the one 275w mono panel on the Rover, bigger panel, bigger controller?? And if I get another 275w panel, the Rover should be able to handle it better. Guess I have just one more dumb question, should I leave the two 100w panels hooked up in parallel or should I switch them over to series before hooking them to the Wanderer?? Thanks again, ClassC

 

[John61CT]

Assuming MPPT able to handle higher volts, test both ways A/B.

But series more sensitive to partial shading (you can test that too).

Ideal is one SC per each panel, well-matched for that SC (or v/v).

But if you have multiple panels per SC, all those panels should match each other. .

 

[frater secessus]

should I leave the two 100w panels hooked up in parallel or should I switch them over to series before hooking them to the Wanderer??

Parallel, assuming your battery bank is 12v.  PWM won't be able to use anything over your Vabs, whether the panels' Vmp is 18.9v or 37.8v.  


Theoretical max output -- no temp or insolation losses included:
parallel 14.8v (Vmp 18.9v) x 5.29a x 2 panels = 156.58w <-- amps double in parallel

series 14.8v (Vmp 37.8v) x 5.29a  = 78.292w <- volts double in series but PWM can't access it. 

mppt 18.9v (Vmp 18.9) x 5.29a x 2 panels x 0.95 MPPT losses efficiency = 190w <-- mppt parallel and serial would be identical most of the time

So you could pick up another 40w by going mppt.  Probably not worth the money unless you can pick on up secondhand.  If your Vabs is lower than 14.8v then the difference between PWM and MPPT would be more pronounced, as PWM makes more power at higher voltage.

 

[ClassC.RV.470]

So what you’re saying is that I should use the Rover (mppt) on the 2-100w panels that are in parallel and use the Wanderer (pwm) controller on the 1-275w panel because it’s a higher voltage panel inorder in get the most out of what I have, correct??

 

[John61CT]

MPPT is what handles higher voltage, more efficient at 40+ volts, in that case up to 90V (open circuit) total.

PWM just wastes any voltage higher than say 19-21V.