Question about the output from my DIY Solar

[pconroy328]

So I could use a "shove in the right direction."

My Solar is all DIY. Two 100 watt panels, an EPEver 30A MPPT controller. One group 27 (for now).

It's working. It's keeping the battery charged.
But I don't think it's working right, or even close to optimal.

The first 100 watt panel is two years old. I started with it, just one 100 watt. I added the second 100 watt panel a month ago - wired parallel.

Wire from panels to controller is 10g stranded from Home Depot.

Thing is I just started watching the power output recently!

Today is FULL SUN, No Clouds, Noon in Denver.
I'm getting 30 watts.

Looking back at historical data for the week, the best I've ever done is 85 watts from the two panels.


Does that happen?

I *am* plugged in and the battery is fully charged.
Is that what's happening?

The controller is smart enough to dial down the wattage since it's not needed?

If I unplugged and discharged the battery - will I see the controller display more wattage from the panels?


(As I'm typing this, I think I'll try that now. Unplug.)

But I'm a bit confused and wanted to hear from some of you.
Thank you!!!

[ajriding]

If concerned check the wattage coming off the panels. It should be about 18.7 or so in any light.

Looking at the MPPT output is only going to tell you what the charger thinks the batteries need at that moment, so, yes, it should almost always be less than maximum unless the batteries are low or power demand is high somewhat.

What panels are they, glass or flexible? It would be more common for a flexible panel to go bad as they typically are installed flat on the roof so do not have any ventilation under the panel; they get very hot and the tiny wires and connections can melt or burn or get other heat-related damage. A glass panel mounted correctly should last for years.

Also, tip: Run the two panels in series to the MPPT controller (it is probably ready for either 12 or 24 volt (18 or 37 volt at the panel) input and it will output either 12 or 24 depending on what the battery it, and it will know all by itself usually.

In series will be more efficient.

[MDKMDK]

pconroy328 wrote:
So I could use a "shove in the right direction."

My Solar is all DIY. Two 100 watt panels, an EPEver 30A MPPT controller. One group 27 (for now).

It's working. It's keeping the battery charged.
But I don't think it's working right, or even close to optimal.

The first 100 watt panel is two years old. I started with it, just one 100 watt. I added the second 100 watt panel a month ago - wired parallel.

Wire from panels to controller is 10g stranded from Home Depot.

Thing is I just started watching the power output recently!

Today is FULL SUN, No Clouds, Noon in Denver.
I'm getting 30 watts.

Looking back at historical data for the week, the best I've ever done is 85 watts from the two panels.


Does that happen?

I *am* plugged in and the battery is fully charged.
Is that what's happening?

The controller is smart enough to dial down the wattage since it's not needed?

If I unplugged and discharged the battery - will I see the controller display more wattage from the panels?


(As I'm typing this, I think I'll try that now. Unplug.)

But I'm a bit confused and wanted to hear from some of you.
Thank you!!!

It's how my Zamp ZS-30A PWM charge controller and 3 X 100W Sun Power panels work. The CC only sends what it sees as the demand at the batteries. Add a load, or unplug from shore, and the amps/volts numbers should increase as the battery discharges. BFL13's numbers are probably spot on, based on your set up.

[time2roll]

Yes unplug and turn on all the lights to add a load. Then post the output.

[KD4UPL]

If your battery is full then the solar charge controller will limit the power to a float charge. Turn on lots of lights and other loads and it should rise accordingly. But, as BFL's math shows, don't think you'll ever actually get 200 watts out of it.

[BFL13]

Panel rated wattage is 200w. Lose 10% from panel heated by sun. Now at 180w. Lose say 2% line loss array to controller. Now at 176ish watts at controller input. Lose 4% controller inefficiency, now at 169w controller output.

Amps to battery is output watts/ battery voltage (with no line loss to battery assumed)

169/12 = 14 amps
169/13 = 13 amps
169/14 = 12 amps

BUT if the battery is nearly full it won't accept so many amps. So the MPPT controller just supplies the "demand" (buck converter in it)

If battery will only accept 2 amps at 13.6v, that's 27 watts.

If you now turn on a light for 3 more amps, the controller will now supply 5 amps and watts will be 5 x 13.6 = 68w.

[red31]

controller job is the LIMIT panel output, if your battery is charged it does not take much power to keep it there.

Yes, if there is a need for power and it CAN be made it will be used for whatever load you have and/or to recharge the battery.

[2oldman]

Sounds like only one panel is working. The controller will dial back the charge rate as needed. I don't know if your controller shows what's coming in from the panels.. that would be a clue.

I've had two panels fail in 15 years. They show burnt spots, black or brown, on the front of the panel. They're the aluminum ribbons that connect the cells together. They get hot, so you want want to check for hot spots.

You can check each panel with a voltmeter, or, temporarily wire in series to see if the voltage doubles.