But at 77f 200 watts is 200 watts.no matter how you slice it?A solar panel, correctly oriented, on a sunny 77 degree day will have a considerably warmer surface. Cell temp and air temp. are two different things. Have you ever picked up a crescent wrench that has been lying in the sun for a while? Same idea.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
@Estragon what are your nominal and peak amps from a 1000 watt array with 12 volt bank?
IIRC, the best I've seen is ~80a on a cool breezy day with broken cloud. In normal conditions more like 50-60a.
Thanks So normally 55 amps 10 % charge rate on a 550 amp hour 12 volt bank with around c/7 when it's putting out 80. But On a 450 ah @ 12 volts 55 amps = 13% with a max of 80 roughly c/6. A 624 bank @55 amps puts me at 9℅ And with 80 amps c/7.8 charge rate. looks to me a 550 is the best match for a 1000 watt array. Question is could I squeak by on a 624 ah bank by doing some bulk if needed. I only have a 300 watt inverter for TV dvd and charging phones. So I normally crank the generator each morning for making toast and using the Microwave and the S.O. blow drying etc. Or would it be a better match with 550 or the 450 battery bank. Suggestions?
Being that im in RV and want to stay 12 volt. With 600 + ahs im thinking for 30 minutes running a 800 watt washer. 5 or 10 minutes of Microwave 900 watts. and a 830 watt toaster 4 slices 5 min. Does it Sound doable ? I'd have 1200 watt hrs available with a 3 day reserve. With 5 avg sun hrs from April - aug would a 1000 watt array produce 3500 watt hrs per day ? Anyone
3500wh/(sunny)day is roughly right for a 1kw array most of the year in many locations, IMHO.
I wouldn't run more than one of the heavy (toaster/microwave) loads at the same time on a 12v system, but one at a time should be doable. Running the genny for heavy loads in the morning sounds like a good plan to me.
Trying to figure temp compensation With this panel. at 86c ambient temp. What would you expect the panel temp to be if it were pole mounted. Full sun at noon.
Just to be clear, what are you asking about temperature compensation? Generally we temperature compensate battery charging voltages (hot batteries, lower charging voltage; cold batteries, higher charging voltage).
With solar panels, their Vmp and Voc temperatures are cell temperature dependent... As the temperature rises, Voc and Vmp fall... However, we generally do not compensate for this other than looking at worst case cold temperature (Voc-cold vs Vpanel-max for MPPT charge controller, and Vmp-hot for hot panels on MPPT charge controllers) and that those numbers fall within MPPT controller specifications. And remember it is cell temperature (Tambient+Trise due to sunlight on cells).
For PWM charge controllers, we generally look at Vmp~17.5-19 volts as "optimum" for solar panels on a 12 volt Lead Acid battery bank (i.e., panels will generally work OK when hot and not "waste" too much energy when cold (due to the way PWM controllers work).
More or less, there is almost a 2:1 range from Voc-cold (subfreezing weather) to hot/no wind/sunny summer days.
Are you looking for the equation for Voc and Vmp vs temperature(s)?
Yes voc and vmp at
correction from last post 30c 86f (not 86c.) Open field 5 mph or so wind. Roughly what temp would the panel be. And how much would it drop the voltage.
The temperature of the panel is what matters, the ambient temperature along with wind will have a cooling effect, test with an inferred thermometer if needed. Checked mine yesterday, 82°C (180°F) on the back of the panels, 44°C (111°F) ambient with no wind, the output was 1240W from 1890W STC , or 65% . Sure they have reduced output but not something to be overly concerned with it is what it is.
Ok, If the light waves from the sun are causing the panels to heat up but some of those waves were being converted to particles ( wave function collapse ) and becoming Photons, then wouldn't it be better to have the panels doing a continuing output to keep them cooler ?
They are running an air conditioner, not sure about wave function collapse and photons, but the UV index of 16 yesterday may have some effect, today panel temperature is 65°C, ambient 40°C, UVI 12 with light breeze.
Ok from what I've read on here. You should bulk charge early and let solar finish. My situation. Being on the north west side of a mountain in a valley. This time of year I get 11 to 3:30 sun on the array. Im Thinking of putting another array closer to the rv where it would get sun (when it shines) from 2-6. 1 array on mppt and one on pwm?? Thoughts??? Any way this time of year at 3:30 or so I crank the generator for ac about 3-4 hours. What if instead of morning charging. I just charge the batteries in the afternoon while the ac is going?? I have the new type Iota with the iq 4. In the Virginia mountains it's either foggy in the morning. Cloudy mid day or raining in the afternoon. Weather forecast says the next full sun day is July 27. Last September had 2 days that it wasn't raining. Lastly If im charging every day at 13℅ or higher with the generator. is it doable to use a 5℅ solar array? This is a Summer only 3-4 month vacation stationary rv.
Yes im in a valley. when I bought the property I didn't consider that I'd need Solar power. because power lines are on my property .Here most days solar just isn't working. @Estragon seems I've read where you charged with a generator and no solar for a while? And that you run 2 45 amp Iotas off a 2000 Honda?