Question about Renogy solar panel system

[Rohan]

Question for the forum about Renogy solar panel system. I'm just not getting the results I need, not even close.

(BTW, I tried to post this to the Renogy support group - but it says my account has been suspended, which is funny because I have never posted there!!)

Recently I bought 2x 100w flexible panels and installed them on the bimini. This was my first time installing solar. I hooked them in series for now instead of parallel. Per the instructions, the wires go from the panels, to the charge controller, to a fuse, to the battery. My boat has 4x very large AGM batteries, all connected together. I attached the wires to one of the batteries.

To experiment, I turned off shore power to see how well the panels would keep my batteries up with my small refrigerator running (which only draws 2.2 amps!). I turned the fridge on the lowest setting and left it that way for a couple days. Returned to the boat, and my battery voltage was 12.9, which is excellent. I was very happy. So I carried the experiment further and set my fridge at halfway setting, came back a few days later. Batteries were drained down to 12.2 which is unacceptable, and those days were pretty sunny too. I couldn't really believe that just changing the fridge setting a couple notches would make that much of a difference! But to make sure, I tried again. I plugged batteries into shore power until they were fully charged, then turned off shore power, turned the fridge back down to the lowest setting, and left for three days (two of which were very sunny).

When I returned the batteries were at 11.9 volts!! Nearly a drained battery. I can't tell you how bad that is. Seriously, by my experience, that's even WORSE than I would normally expect if I had left for three days with no solar power at all. So what the heck is happening?? How did I go from 12.9v to 11.9v?

By comparison, I have two buddies in the same marina with similar sized boats and refrigerators. One has 2x 40w panels, and the other has 1x 50w. Yet both of them brag that they never need to plug into shore power because the panels keep their fridge running and batteries topped off. Yet I have four times that amount of solar and my battery is dying??


I have read the manual many times, and I don't see anything I did wrong. The charge controller indicates that everything is charging normally. It should give an error message if I hooked things the wrong way. It displays that I am pulling in up to 6 amps in the middle of the day when it's sunny, to about .1 amp in the evening or very cloudy day.

Here's one anomaly I can't figure out and this might be related to the problem. The display shows my battery voltage, which always agrees with my voltmeter. But it also shows something else called "photovoltaic array voltage". What does that mean? The manual doesn't explain. The crazy thing is, sometimes that voltage will read 12.6v or so, about the same as my battery voltage, and sometimes it reads 39 to 40 volts!! Where does come from? Even if it's adding all four of my batteries together, that should be like 48 - 50 volts or so.

Anyone have an idea why this isn't working for me?

[George_SD]

Rohan, a strong suggestion to google and read up on how solar systems work. There are a lot of details missing in your description to provide any sort of a sensible answer.

Panels need to be sized to loads/battery banks. Wiring must be of correct size and length. Amount and intensity of light , panel position, angle, shading, efficiency, charge controller, programming, battery type, electrical needs, etc all mater and have to be done right for the system to do what you want.

[noelex 77]

Originally Posted by Rohan

Here's one anomaly I can't figure out and this might be related to the problem. The display shows my battery voltage, which always agrees with my voltmeter. But it also shows something else called "photovoltaic array voltage". What does that mean? The manual doesn't explain. The crazy thing is, sometimes that voltage will read 12.6v or so, about the same as my battery voltage, and sometimes it reads 39 to 40 volts!! Where does come from? Even if it's adding all four of my batteries together, that should be like 48 - 50 volts or so.

The photovoltaic array voltage is voltage the solar panels are generating. As you have connected the panels in series, this should be around 39-40v all the time. In relatively dull conditions the amount of current the solar panels can produce will severely drop, but the voltage should remain at around this level.

The good news is that the drop in photovoltaic array voltage down to 12.6v gives you some clue as to nature of the problem. This suggests a poor connection between the solar panels and charge controller. This is not a definitive diagnosis, there could be another fault causing your low production, but the first step is to double check these connections.

Good luck.

[Rohan]

Originally Posted by George_SD

Rohan, a strong suggestion to google and read up on how solar systems work. There are a lot of details missing in your description to provide any sort of a sensible answer.

Panels need to be sized to loads/battery banks. Wiring must be of correct size and length. Amount and intensity of light , panel position, angle, shading, efficiency, charge controller, programming, battery type, electrical needs, etc all mater and have to be done right for the system to do what you want.

Maybe I should have added one more detail then - I didn't provide those specifics because I bought this system as part of a kit, everything included, so I can assume the wiring is the correct size, etc. Specifically it was this kit right here:
https://www.renogy.com/200-watt-solar-flexible-kit/

The panels are slightly curved on top of my bimini. Zero shade around other than from the boom. But I don't think shading or position is a factor because while my results changed, my boat's position and the overall weather hadn't changed at all.

[Rohan]

Originally Posted by noelex 77

The good news is that the drop in photovoltaic array voltage down to 12.6v gives you some clue as to nature of the problem. This suggests a poor connection between the solar panels and charge controller. This is not a definitive diagnosis, there could be another fault causing your low production, but the first step is to double check these connections.

Thanks, the connections seem solid but I will definitely look into that more closely.

[noelex 77]

Ah, the link makes things clearer. That is a PWM regulator not a MPPT controller.

You cannot connect the panels in series (for a 12v battery) with this type of regulator.

Change to parallel connection and all will be well.

[Dsanduril]

Originally Posted by Rohan

... It displays that I am pulling in up to 6 amps in the middle of the day when it's sunny, to about .1 amp in the evening or very cloudy day...

Originally Posted by noelex 77

Ah, the link makes things clearer. That is a PWM regulator not a MPPT controller.

You cannot connect the panels in series (for a 12v battery).

Change to parallel connection and all will be well.

As Noelex so astutely pointed out. 6A @ 14V ~84W, pretty good for a single panel, but with the PWM controller all you can get is the current from the single panel, you're wasting all that photovoltaic voltage. Switch to parallel and you should see 12A under the same conditions. Or switch to an MPPT controller and probably see a bit more.

[Stu Jackson]

Originally Posted by Rohan

>>>>>>>>>>>>>>>>>
The panels are slightly curved on top of my bimini. Zero shade around other than from the boom. But I don't think shading or position is a factor because while my results changed, my boat's position and the overall weather hadn't changed at all.

Of course it did. In series, ANY shading will drop output dramatically.

[flee27]

And the OP stated he has the wires connected to one of the batteries. The output from the solar controller needs to be attached across the bank, not one battery. This goes for any other charger or load source also. The bank needs to be treated as one battery.

Would be helpful to attach a quick sketch of you basic electrical system. The more details that can be provided the more help that can be given.

Foster

[Rohan]

Originally Posted by flee27

And the OP stated he has the wires connected to one of the batteries. The output from the solar controller needs to be attached across the bank, not one battery. This goes for any other charger or load source also. The bank needs to be treated as one battery.

So you mean attach the positive lead to a battery on one end, and the negative lead to a battery on the other end? I can try that.

Would be helpful to attach a quick sketch of you basic electrical system. The more details that can be provided the more help that can be given.

Not really necessary to draw a diagram, it's pretty simple. I just have two banks of 2xAGM batteries each. I can flip between one bank or the other but kept them all online for solar charging.

[Rohan]

Originally Posted by Dsanduril

Switch to parallel and you should see 12A under the same conditions. Or switch to an MPPT controller and probably see a bit more.

Thanks, I will definitely try that too, and report the results here, although may take a couple weeks.

[Spot]

Originally Posted by Rohan

So you mean attach the positive lead to a battery on one end, and the negative lead to a battery on the other end? I can try that.

Not really necessary to draw a diagram, it's pretty simple. I just have two banks of 2xAGM batteries each. I can flip between one bank or the other but kept them all online for solar charging.

Hi Rohan, a diagram would help capture details quickly both for presentation now and retention in the future. Does your system look something like this, assuming you make the change to parallel panels?

[Rohan]

Originally Posted by Spot

Hi Rohan, a diagram would help capture details quickly both for presentation now and retention in the future. Does your system look something like this, assuming you make the change to parallel panels?

That's pretty close, although I hooked both the wires from the solar charge controller to the battery terminals directly, not to the battery selector switch.

[ikanode]

Originally Posted by Rohan

The crazy thing is, sometimes that voltage will read 12.6v or so, about the same as my battery voltage, and sometimes it reads 39 to 40 volts!! Where does come from? Even if it's adding all four of my batteries together, that should be like 48 - 50 volts or so.

Your batteries are connected in parallel so they should be 12-14 volts.
Hooking up the panels in serial is for a 24v battery system.

Before doing much else, you need to learn about parallel vs series connections and the impact on voltage and current. Here's one expanation
https://www.batterystuff.com/kb/arti...-tutorial.html

[waterman46]

Originally Posted by Rohan

That's pretty close, although I hooked both the wires from the solar charge controller to the battery terminals directly, not to the battery selector switch.

Which battery terminals did you connect to? That diagram is correct. You need to connect the + solar output to the common +12V bus, not to one or the other batteries and certainly not directly to both banks at the same time.

And be sure your solar controller negative is connected to the 12V negative bus of your boat.