My Solar Install

[tony.latham]

and now I'm wondering if I made a mistake ordering a PWM controller.

Tom:

a PWM controller would almost never work--the voltage would never reach 12 volts.

The controller controls the charging volts. Since it is set for an AGM, it's charging... what is it, 14.7 volts or something like that? A panel that isn't facing directly at the sun puts out less wattage.

I jumped from an 80-watt folding set of panels to a 100-watt roof-mounted panel this summer.





I was concerned that this non-optimized panel might not produce enough energy. I had left room on the roof for another 100-watter if need be... but...

Early in the summer, I watched the system like I was sitting in a prime seat watching the World Series. The first thing I would do in the morning was to check how many amps we had used. (Invariably, it was 8-10 amps, mostly from me sucking on my CPAP.)

Then I'd sit down with a cup and watch the app on my phone (via Bluetooth) tell me how much the system was producing. As the sun rose, the production would start out slow and increase the higher the sun rose of course. Invariably, about the time the system was producing the max 7-8 amp/hours, it would start shutting output down because the battery was near capacity. Frequently the controller would limit the output well before the panel reached max production.

So here's the answer: I like the roof-mount better than the portable panels. No more chasing the sun.

Fixed roof panels are fine. Keep in mind that residential solar systems (including ours) seldom use tracking systems anymore.

Tony

I always do what Tony does...

Does this make me a cult leader with one member?

[tony.latham]

Over the years I’ve amassed a small collection of 50 watt solar panels.

Well damn, Tom. It's about time you got something up and cooking.

Energy is good. I'm sure you'll be pleased with that setup.

Tony

[Tom&Shelly]

I was concerned that this non-optimized panel might not produce enough energy. I had left room on the roof for another 100-watter if need be... but...

Early in the summer, I watched the system like I was sitting in a prime seat watching the World Series. The first thing I would do in the morning was to check how many amps we had used. (Invariably, it was 8-10 amps, mostly from me sucking on my CPAP.)

Then I'd sit down with a cup and watch the app on my phone (via Bluetooth) tell me how much the system was producing. As the sun rose, the production would start out slow and increase the higher the sun rose of course. Invariably, about the time the system was producing the max 7-8 amp/hours, it would start shutting output down because the battery was near capacity. Frequently the controller would limit the output well before the panel reached max production.

So here's the answer: I like the roof-mount better than the portable panels. No more chasing the sun.

Fixed roof panels are fine. Keep in mind that residential solar systems (including ours) seldom use tracking systems anymore.

Tony

Nothing like real data! Thank you Tony.

I always do what Tony does...

Does this make me a cult leader with one member?

Possibly more than one. But please don't ask me to drink any koolade! I heard it can rot the teeth!

Tom

[saltydawg]

Then I'd sit down with a cup and watch the app on my phone (via Bluetooth) tell me how much the system was producing. As the sun rose, the production would start out slow and increase the higher the sun rose of course. Invariably, about the time the system was producing the max 7-8 amp/hours, it would start shutting output down because the battery was near capacity. Frequently the controller would limit the output well before the panel reached max production.

It would be interesting to have you discharge for 2 or 3 days and see what the curve is like vs sun angle. It would also be cool to see the voltage right off the panel. So volts and amps off the panel, vr volts and amps off the pwm vs angle of the sun. But over a 4 or 5 hour period where your battery could take it all.

No need to get super detailed, a reading every 2 mins would be fine.... sarcasm

[Socal Tom]

I've got a 100-watt panel on the roof and a 30-watt panel on the tongue box. The panels are controlled with a PWM controller.

I went with a PWM because MPPTs are big and more expensive.

We use 8-10 amps per night. (Mostly from my CPAP).

Even in the camp above with a canopy and a broken cloud cover the battery was charged by noon. If we're in the open, it's charged up by 11:00 at the latest ––depending on how high the ridges are to the east.

Sure, I could change the controller out with an MPPT .... but why do I need a more efficient system?

Tony

Pretty good data. And a system similar to Socal Tom's.

Not to hijack the thread, but I bought a cheap 100 W panel and the identical (I think) PWM controller to Tony's, with the intention of installing the controller in the 'drop and that particular panel on either the roof or SW facing wall of the garage. Spent some time today trying to calculate the best angle for pointing the panel. (Later, I'll buy a different panel for use in the field, or perhaps for mounting on our teardrop.)

Since both of your panels are basically horizontal, if the voltage out of the panels were strictly proportional to the (cosine of the--but never mind that detail) angle of the Sun to the panel, a PWM controller would almost never work--the voltage would never reach 12 volts. Since Tony's system works (well), that's obviously not how the panels work! Most of the power drop due to imperfect pointing must be the result of current (amperage) out of the panels.

Later, I plan to install more panels on the garage for lighting and small power tools. For that, I'll buy a (larger and heavier) MPPT controller, along with an inverter, and a battery bank independent of the teardrop's.

Oh, and the reasons I bought the PWM controller: A. I always do what Tony does, except when I don't. 2. That particular controller was designed to mount on a panel and hide the wires behind it. Only other solution I found were some controllers with optional (and spendy) remote controls and/or blue tooth modules.

Again, sorry for the hijack Tom. I like your mounting! We may steal the idea.

Tom

Fwiw, I was watching mine like a hawk this past trip. I have one of the fancy Baylite meters, I used about 180 to 220 watts between sunset and sunrise. I was honestly surprised to see the panels start charging before 7 am. It was very slow, less than an amp, but charging. Voltage was Over 13.6 by 11.30, and at the cutoff by 1. The panels are rated at 2.9amps output, I saw a peak of a bit over 6amps but at that point the battery was pretty well charged.

[Socal Tom]

another good test video

https://youtu.be/-WGU5j7Rh1g

direct comparison video

https://youtu.be/fSsrEzDcGf8

this video he does not show the actual power out put from pwm. He does show the weather and the output from the mppt charger. As he says take it with a grain of salt. He also mis speaks a few times but does correct himself. Snowy weather he is getting 150 to 200 % more power on the mppt chargers, from what he says.

Again it depends on your install if you should go mppt. On a shed roof throwing another 80 buck 100 watt panel might give you twice the bump of a mppt charge for the same price.

It’s my understanding that solar panels aren’t necessarily 1 “panel”, they are grouped into smaller portions so that if the output from one portion goes below 12v, due to shade, that portion is shutoff. So if you have 4 sub-panels in a 100w panel, shade in one corner should drop output 25%.

[saltydawg]

It’s my understanding that solar panels aren’t necessarily 1 “panel”, they are grouped into smaller portions so that if the output from one portion goes below 12v, due to shade, that portion is shutoff. So if you have 4 sub-panels in a 100w panel, shade in one corner should drop output 25%.

Watch the one video where he blocks one corner the whole panel dropped out.

Your talking about cells. each little rectangle is a cell, so many cells make up a panel. It depends on the panel design and size. Some larger panels may have 2 groups of cells, each group will have the cells in series, but it may have 2 groups in parallel. But I dont really know.

If they are parallel then yes one panel will just drop out, if they are series it can take out the whole array. There are panels that have bypass diodes, that will let the power bypass the shaded/blocked panel. I dont know which ones they are, but in our small array world it does not matter.

[Sparksalot]

and now I'm wondering if I made a mistake ordering a PWM controller.

Tom:

a PWM controller would almost never work--the voltage would never reach 12 volts.

The controller controls the charging volts. Since it is set for an AGM, it's charging... what is it, 14.7 volts or something like that? A panel that isn't facing directly at the sun puts out less wattage.

I jumped from an 80-watt folding set of panels to a 100-watt roof-mounted panel this summer.





Which 100 watt panel did you go with?
I was concerned that this non-optimized panel might not produce enough energy. I had left room on the roof for another 100-watter if need be... but...

Early in the summer, I watched the system like I was sitting in a prime seat watching the World Series. The first thing I would do in the morning was to check how many amps we had used. (Invariably, it was 8-10 amps, mostly from me sucking on my CPAP.)

Then I'd sit down with a cup and watch the app on my phone (via Bluetooth) tell me how much the system was producing. As the sun rose, the production would start out slow and increase the higher the sun rose of course. Invariably, about the time the system was producing the max 7-8 amp/hours, it would start shutting output down because the battery was near capacity. Frequently the controller would limit the output well before the panel reached max production.

So here's the answer: I like the roof-mount better than the portable panels. No more chasing the sun.

Fixed roof panels are fine. Keep in mind that residential solar systems (including ours) seldom use tracking systems anymore.

Tony

I always do what Tony does...

Does this make me a cult leader with one member?