Solar Panel Voc-MPPT?
Wondering if there is any relationship between measured Voc and MPPT performance with a 24v panel. My 12v panel has a Voc rating of 21.9 and Isc of 8.2, but I often see 8.2ish when Voc is only 20....
Forum Discussion
BFL13 wrote:red31 wrote:BFL13 wrote:
“Annual income twenty pounds, annual expenditure nineteen six, result happiness. Annual income twenty pounds, annual expenditure twenty pound ought and six, result misery.” Dickens.
How about an over/under pool? pic a voltage and amp, same location, same time of year, solar noon, clear blue sky ...
If the over/under is 16A @13.5, put me down for under
230w with 12v and PWM would get me 14.5a until low 13s. By 13.5 I would notice a slight drop due to the IV curve. Happiness would be to get more than 14.5 with MPPT -- at least another 1.5a for 16a.
So under 16 is misery! However, there is also the claim that MPPT does better on daily AH haul by doing better in the shoulder hours or in poor light, even if it does little better an actual amps at noon.
Seems kind of lame in comparison with just seeing way better amps on the Trimetric.
That would be harder to notice and measure too. Have to repeat those tests from a couple years ago. Be a desperation last ditch attempt to prove I didn't waste my money if I only get 15a instead of 14.5
I knew that going in though, which is why I only did it when I was going to have to get a new PWM controller anyway so the diff in price in moving "up" to the Eco-Worthy at $108 was "worth a try." Maybe the thing only works at 10,000 ft and you need a Sherpa to carry it up there for you like JiminDenver does. :)
BFL.
In mid summer and bright peak sun with my batteries (4 T-125's) down to the 60% SOC or lower I see 11.5 - 12A out of my 160W panels with the sunsaver controller. Translating that to 230W says you should see between 16 and 17 A peak under these conditions.
Even translating my recent fall results at 80%SOC of 10.1-10.4 A/160w panel would give you about 14.5-15A A in late fall with batteries in the 80% SOC range. Probably another 1/2 to 1A when the batteries are more depleted.
Under those conditions my PWM controller gave me 9.5A which should equate to about 13.5 with 230W.
conclusion: I think in summer sun, you will see 16A
In the fall/winter and high latitude, my panels can only output slightly more energy (watts) that a direct connection to the battery can absorb (PWM), so there isn't near the gain you get in the summer.
but then, this time of year is pretty much end of camping season for us anyway.
