Single or Multiple Panels?

[klpauba]

Originally Posted by rickst29

Definitely DON'T do anything like that! Those "Stayput" clips require you to pierce the shell - which was easy for the boater with fabric, and possibly necessary because the fabric can wear out over time and flap around in strong winds - but a terrible thing to do to a TM shell, which is solid, stable, and waterproof (unless you "screw it up" on purpose).

Although I have a number of different ideas for mounting that I have to think through, none of them involve putting holes in the roof. In this case, I was thinking of gluing the track to the roof (with VHB tape) and then having the stayput clips mounted to the track.

Originally Posted by rickst29

That's another reason to prefer two flex and one "solid" - with double flex panels, you mount the solid-framed panel above the midline, and you don't have to worry about the bump at all.

Ahhh, that makes a lot of sense! All in all, I have to admit that the one glass and two flex is the way to go (at least for me, anyway).

[klpauba]

Originally Posted by rickst29

And, I speak from actual experience in INTENSE sunlight (altitude 9000 ft). My aluminum-framed panel surfaces, with air underneath, get much hotter than the flex panel surface.

This is really good to know. My thoughts of adding a polycarbonate sheet (with integral air channels) would be unnecessary.

[rickst29]

By the way - the tape which I recommend for the flex panels (and the framed-panel mounting feet) is 3M "VHB" version "RP32", width 1". You'll need about 260 inches to handle the two flex panels, plus another 16 - 24 inches for the "solid" panel (16" using 4 mounting feet, 24" if you add another pair of feet as "overkill"). The total is a bit more than 7-1/2 yards, so you'll need two 5-yard rolls.

"RP25" is also usable, but a bit thin - the roof shells do need a bit of "flex", especially while dropping them down and clamping them in for travel. Thicker versions, in my opinion, have a bit too much sideways flex, and reduced "shear" strength, and don't transfer heat to the TM roof quite as well. (Therefore 4941, at 45 mils, seems a bit too thick.) In practice, though, all 3 thicknesses would work fine.

Since neither the flex panel bottom sheets OR the TM roof allow humidity to reach the middle of the tape, I would buy a set of the "primer" sticks too. Clean your tape surfaces really well - first a grease-cutting cleaner, and then take off cleaner residue using slightly watered-down IPA. (At about 50% water, 50% alcohol- the bottles start at 70% IPA, so you're adding about 1/4 as much additional purified/distilled water into the mix). Then the primer, then the tape segments. To make it easy, I used multiple short segments, and didn't try to do the entire length of my Flex Panel with a single piece. I started with the Flex panel loosely rolled up - unrolling the panel, sticking on tape segments, and pressing it into the roof in 3 segments, rather than juggling the entire thing at once.

[klpauba]

Is it enough to test new solar panels for the open circuit voltage and short circuit current only or should I bother getting a 100 W rheostat and check it (by ploting the power curve) under varying loads?

[scrubjaysnest]

I just check for Voc, open circuit voltage and Isc. Isc is the hard one as you'll need full sun to get close and it may be better if ambient air temp is 80 deg F or lower. Any kind of good sun will let you get Voc readings. For the short circuit current I figure with full sun any value greater then Imp is close enough.

[rickst29]

Test the output on the driveway before removing the plastic "protective film" which they add on top, to prevent shipping damage. Solar panels are not damaged by connecting through loads with near-zero resistance, so you can test both Voltage and Amps with a cheapo multimeter. (Just connect the meter itself across the two terminals, as the only load). The resulting Voltage should be quite near V(oc).

But: With the protective film still on, and later-winter sunlight conditions, expect the Amps to besignificantly be lower than I(mp). I'd expect to see V(oc) * I(sc) to calculate only about 50-60 watts from 100W "flex" panels at this time of year, with the "film" still attached.

The glass panel CAN have the protective cover completely removed for test before mounting - though of course, with all panels, tape a BLACK garbage bag on top of the entire cell surface after testing, while you take them up to the roof and wire them together. Don't forget, your configuration is wired in Series. Ignore the "danger! danger!" graphic at the bottom of the Ebay item I pointed to earlier - it doesn't apply to you.

After connecting the MPPT monitor the MPPT, the Battery RTS to the MPPT, and connecting the two "long" wire ends into the MPPT "Solar +" and "Solar -": Connect the "+" and "-" battery wires from MPPT to the batteries. The MPPT (and it's monitor) will power up. Now modify battery parameters in the MPPT to match your brand of batteries.

Be sure to MARK your two long wire ends as shown at the MPPT, "+" and "-", before routing them. From MPPT location to the outside, then up to the roof using one of the the lift arms - with a little "extra" length to handle changes in distance from shells-down to shells-up) Then connect as follows:

MPPT Solar "-" -----(long)----> Flex-1 "-". then
Flex-1 "+" to Glass "-". then
Glass "+" to Flex-2 "-". then
Flex-2 "+" -----(long)-----> MPPT Solar "+"

The take off your plastic bags, and verify total voltage (at the monitor) for the Solar array is about 53V. If that part worked correctly, then you're ready for it all works, then you can
Done right, after you make your final connection on the Solar circuit and when you take the bags off and turn on the Fridge to eat some power: About 53 Volts on the "Solar" side. That's the sum of V(mp) for the 3 panels.

That's the end of the job for Solar alone.
If you're crazy, magical "switching" of Solar versus boosted TV power could be added later - using the single MPPT controller, and a carefully selected Relay.

[klpauba]

Thanks for the replies, scrubjaysnest and rickst29!

While I just wanted a plan for checking new panels, all of the additional information will help me to get them hooked up right. I'll let y'all know when I get the panels in and will share with you my test results.

I remembered today that my dad has a nice "carbon pile" (I think that's what it's called) that he used to load test batteries and alternators. I was going to use that to help test the panels although it never even occurred to me that the spring sun is much less intense. With the information you provided, I'll just do a preliminary check and then rely on the MPPT to give me more detail when summer is here.