300 W on a 2720SL -- 2 flex & 1 rigid

[klpauba]

Thanks, Padgett. I've read many of your posts for inspiration on this (and other) mods.

I had actually purchased the panels early last year but didn't get around installing them until now. I figured if I didn't install them soon, technology would pass them up and I'd then direct my attention to the new stuff. I really wanted to put them to good use. Last summer I committed to a camping spot without any hookups so that finally got my butt in gear (and I leave in 10 days! )

[Padgett]

You are welcome.

[klpauba]

Late last week I got most of the solar system wired up. I ran solar power wires to the controller -- the positive line is interrupted only by a DC breaker used as a disconnect switch. Here's a shot into my electrical room as it stands for the solar testing:



I've seen 200-210 Watts coming from the solar panels (as reported by the EP Solar MP-50 display) as it sits in my driveway. Unfortunately, I have a blue spruce SE and a mid-sized maple tree SW of the TM so I only have only an hour or two of unobstructed sun around solar noon. I might sneak away at lunch one of these days to add more loads to see how the panels and controller perform if there's suitable sunshine.

I'm currently working to add the remaining components that will allow my TV to provide an alternative 24VDC charging source to the solar panels (there's another thread on that).

I'm feeling the pressure in getting this all done and preparing for a 10-day trip on Saturday!

[klpauba]

I finished up my wiring of the controls that allow me to use a booster in my TV to supply 24V through the Bargman connector to switch the input to the charge controller from the solar panels to the Bargman power connection. Using a process outlined by rickst29, I've verified that I can supply very near the 280W of power from the TV.

Just a few days ago, I found that I was getting more than 200W of power. A couple of days later, a load test of the solar system showed 180W and today I wasn't getting anything (13.1V at 0.00A !!!). Rickst29 has given me instructions to help identify the faulty panel(s). I tested each of them before installation and I shutter at the thought of trying to remove even one of them since the VHB tape seems to work really, really well. This is all happening just two days before I leave for our no-hookups campsite. At least I have the TV Booster and a 2500W genny as backup but I wasn't really planning on using them.

[klpauba]

I was able to isolate the bad panel -- it's one of the flex. I wired the other two in series so I'm now running at 200W. My next step will be to open up the junction box at the top of the panel and check the bypass diode. If that checks out OK, I'm probably stuck with trying to replace the panel.

Let this be a lesson to others. Don't delay installing your panels so that you miss out on the warranty!

[BrucePerens]

If you are lucky, it's a diode, and it's in a junction box that you can open.

I remain dubious about the lifetime of flex panels on a trailer roof. It gets hot and there is no no heat flow from the back. Photovoltaic cells don't like heat and lose efficiency in operation when hot, and maybe break more easily as well. I am dubious about Elon Musk's solar roof for the same reason.

Use framed panels and feet that you can remove them from, and leave room for air flow behind them. Yes, they are heavy, but they last and can be serviced.

[Padgett]

BTW no reason you cannot just set outside, wire up temporarily to a battery and test operation then install. Lots easier to work on before installed on roof.

Mounting a wireless back up transmitter for back up camera with type F antenna to the panel (offset from AC) gives line of sight to the TV. No more wiring needed.

I prefer monocrystalline panels to poly. Cost a little more but have better performance when hot.

[scrubjaysnest]

Originally Posted by klpauba

I was able to isolate the bad panel -- it's one of the flex. I wired the other two in series so I'm now running at 200W. My next step will be to open up the junction box at the top of the panel and check the bypass diode. If that checks out OK, I'm probably stuck with trying to replace the panel.

Let this be a lesson to others. Don't delay installing your panels so that you miss out on the warranty!

This is a nice install; with regards to the bad panel......a quick and dirty check before installing is place the panel in full sun not wired up. Check the open circuit voltage, it should be Voc for the panel. Next short the panel and you should get very near Isc for the panel. These test will not damage the panel.

Let me know via pm if you want your install added to the owner install thread.

ken

[klpauba]

... I did the Voc test when they first arrived but didn't realize I could short them without damage. I'll add that test when I get around to it this weekend.

I then plan to remove the bypass diode and test it as described at http://http://www.ebay.com/gds/How-T...5730702/g.html.

I'm open to other suggestions from anyone so please offer them!

[klpauba]

... a small circuit board. The board was potted but it didn't seem to be epoxy. It flaked away pretty easily. It's hard to see, but two small ring terminals are at the very left and right sides of the plastic box (the screws holding them to the board are removed and shown near the center of the photo). The three large globs of solder connect the three power tabs from the string of cells (2 of them, I suspect) and the surface-mounted diodes are between them.



The positive line is on the right so I think the arrangement of the diodes would be like this:

(-)--*-->|--*-->|--*--(+)

Where (-) and (+) are the negative and positive wire connections, * is a power tab from the string of solar cells and ->|- is a bypass diode.

Can someone verify this?

Since the circuit board isn't really serviceable, is there any easy way that I can test the diodes on the board? I plan on cleaning up the power tabs and soldering diodes directly to them (and the wire connections). I measured the open-circuit voltage (Voc) of the panel at around 18 volts today in bright sunlight (the spec says 21.6) and I shorted the panel and read just 0.48 amps (way off from the 5.62 on the sticker supplied with the panel).

Ebay has US-sourced schottky bypass diodes (15A) available. I'll wait to hear any comments that you might have before I order them on Monday (I have to buy 10 at about $1 each).

Thanks