Years ago, I bought two used PhotoComm, Inc. MSVX-24 solar panels. That's pretty much all the information that is on the tag, and attempts to search these panels' specs out have been fruitless. I know how to test for voltage and short-circuit amperage, but based on these readings how do I figure out what these panels will actually return to my batteries through my Morningstar Sunsaver 6 charge controller?
2003 F250XL 4WD 7.3L Crewcab LB, 6 speed; Prodigy brake controller; Big Tex grille guard/ deer deflector. Canoe hauler and camping truck extraordinaire!
2003 Layton 242 Scout- Extra batteries, solar panels, LED lighting, and propane for boondocking.
Thanks, folks. I just wasn't sure what voltage to multiply the amps by- 12, 14 out of the charger, 17 out of the panel, etc.? From what BFL13 says, it looks like I'm complicating it too much! I'll test the panels the next sunny day we get when I am home at noon, and post the numbers.
Based on my limited experience, the Isc you take at high noon is pretty close to what the panel will do for amps into the battery at high noon. Ignore Voc, it is just goofy--use the Isc which works ok.)
Two panels will do twice that. You need a way to get your full daily AH haul, depending on the 'bell curve' you get for amps all day depending on your location and time of year. A Trimetric is good for that job)
Your actual panel wattage does not matter very much in real life. The way they work is that the max power (panel rating in watts) occurs with fewer amps than Isc (called Imp at Vmp) --it's all BS. Ignore it. Just get your max amps at high noon on a sunny day with the panel oriented properly (South tilted up for your Latitude and time of year) and work with that.
Here are the amps I got various ways, so you can take your noon amps and plot your own bell curve in proportion.
No need to apologize- your assumption is right! It is a 12-volt (nominal) system. Your post is very helpful. I'll put the numbers up (probably tomorrow before I have a chance to get the readings) and let y'all see what you think.
I managed to test these panels today in somewhat less than full sun (about 3:00 in the afternoon). I got readings on both of 20.9-21.0 volts open circuit and 1.29-1.30 amps short circuit, depending on how I juggled the panels, meter, connections, etc. with only two hands! It looks like these are at least 24-watt panels, I think (?).
Thanks very much for your help! Safe travels,