Solar: Wattage output

[thomm225]

Originally Posted by john61ct

Unmatched panels should be on separate SCs anyway

I'd say it's better if they are but they don't have to be.

I've had my 20 and my 65 watt panel in parallel to the Victron. The 50 and the 65 watt panel to the Victron in parallel also.

I've done the same with the PWM controller

Now though since I have a 12 volt fan and am not wasting so much power running a 120 volt fan thru an inverter, I may only need the 65 watt panel, but for now I'm using the 65 watt thru the Victron and the 50 thru the PWM which has a voltage display

If I need more, I'll hook my 20 watt panels up directly to the batteries for a few hours …….

[john61ct]

Why I used "should" rather than must

[thomm225]

Originally Posted by john61ct

Why I used "should" rather than must

As mentioned, the only problem I've had was with the connections at the controller with more than one panel.

It didn't matter whether the panels matched or not it was just the space etc at the connection points

[Cpt Pat]

Originally Posted by thomm225

As mentioned, the only problem I've had was with the connections at the controller with more than one panel.

It didn't matter whether the panels matched or not it was just the space etc at the connection points

Provided all of your panels have the same - or nearly the same - maximum power voltage, using just one controller and a parallel-connected array will work just fine. The maximum power voltage doesn't change appreciably when a panel is shaded. If you are concerned about loss due to reverse current flowing into a shaded panel: use steering diodes (Schottky diodes preferred) in series with each panel. Good ones cost about 50 cents. Compare that with the cost of a controller. Yes, there will be a tiny amount of loss through the diode. For panel with a 17 volt maximum power voltage panel, you'll lose about 1/50th (2%) of its power - high voltage panels - less loss. Compare that will the power consumed by a controller.

Controllers consume some power too. That's why they get warm or hot. More controllers consume more power.

I have 10 parallel-connected panels that are 15 watts each. No, I am not going to install 10 charge controllers. If I were that crazy, I'd shop around for a nuclear reactor. Proponents of the "one charge controller per panel" theory must be shills for the MPPT controller manufacturers.

Keep in mind that the panels themselves have parallel-connected sections of cells. If we really want to go nuts, according to that theory, each of those parallel-connected sections should have its own charge controller. The whole concept rapidly passes the point of diminishing returns to the point of loss due to absurdity. Save your money -- buy more panels.

[Stu Jackson]

Originally Posted by john61ct

>>>>>>>>>>>>>>>>>>>>

As SoC climbs, energy will flow much more slowly until only a fraction of the potential available.


>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>

If your batteries are full or close to it, where would the power from the panels go?

[Captain Bill]

Originally Posted by Stu Jackson

If your batteries are full or close to it, where would the power from the panels go?

Unless you are using it to power a load, no power is produced once the batteries are full. In actuality a tiny amount of power is used to power the controller, but effectively an mppt controller opens the circuit and the panel goes to open circuit voltage and 0 amps. Since power = Voltage times amperage power is 0.

[thomm225]

Originally Posted by Cpt Pat

Provided all of your panels have the same - or nearly the same - maximum power voltage, using just one controller and a parallel-connected array will work just fine. The maximum power voltage doesn't change appreciably when a panel is shaded. If you are concerned about loss due to reverse current flowing into a shaded panel: use steering diodes (Schottky diodes preferred) in series with each panel. Good ones cost about 50 cents. Compare that with the cost of a controller. Yes, there will be a tiny amount of loss through the diode. For panel with a 17 volt maximum power voltage panel, you'll lose about 1/50th (2%) of its power - high voltage panels - less loss. Compare that will the power consumed by a controller.

Controllers consume some power too. That's why they get warm or hot. More controllers consume more power.

I have 10 parallel-connected panels that are 15 watts each. No, I am not going to install 10 charge controllers. If I were that crazy, I'd shop around for a nuclear reactor. Proponents of the "one charge controller per panel" theory must be shills for the MPPT controller manufacturers.

Keep in mind that the panels themselves have parallel-connected sections of cells. If we really want to go nuts, according to that theory, each of those parallel-connected sections should have its own charge controller. The whole concept rapidly passes the point of diminishing returns to the point of loss due to absurdity. Save your money -- buy more panels.

Yeah, I'm a tech by trade (tech manager now) so I knew mixing the panels was fine, but I must say that when I had say my 65 watt panel attached to the same controller as my 20 watt panel at times I noticed I wasn't getting anywhere near the power I should be getting.

It was the connections. I would just move them a bit with my fingers (at the controller) and the power would jump back up

I think one set of wires I had "tinned" while the others I had just removed the insulation.

So, I do like my current setup with the 50 watt panel to the PWM Controller, and the 65 watt panel to the Victron MPPT. The PWM has a voltage display also so I can see the voltage just by looking at that controller which is in the lazarette.

If I need more I'll hook the 20 watt panels directly to the batteries with alligator clips

[Stu Jackson]

Originally Posted by Captain Bill

Unless you are using it to power a load, no power is produced once the batteries are full. In actuality a tiny amount of power is used to power the controller, but effectively an mppt controller opens the circuit and the panel goes to open circuit voltage and 0 amps. Since power = Voltage times amperage power is 0.

Thank you, Bill, as always a cogent and factual post.


I'd posted that question almost as a rhetorical one, though.

[john61ct]

Yes thinking that it was sincere, it did surprise me, thought "he knows more than that!"

Snark can confuse the noobs though. . .