Portable Solar Light System Beginner Advice

System

I am trying to design a portable solar system to run LED spot lights for an art festival tent (72 watts but want to shoot for 100 for growth and inefficiency). I would like to NOT have to recharge the system overnight with a charger and instead have enough capacity to recharge during the day, but I may resign myself to recharging until I can afford 2 panels if one is not sufficient. From my rough calculations (see figures below from online calculator), running this system for 8 hours a day mostly in Florida or summer days in the north, with a manageable (65 lbs.) 110ah AGM battery, I am trying to decide on the solar panels for such a system. I would also like the system to be useable as a standalone non-solar array system, but likely without the same daily run time of 8 hours (still trying to figure the math of when I get to 50% capacity). Some of my numbers indicate a 185 watt panel might actually work, but I think this is optimistic (though my draw is not very high). I plan to mount the panels where the awnings are located on a tent, but for optimum exposure I might possibly raise the panel(s) above the tent using the frame as a base.

Although I would like to minimize cost, portability is just as crucial (though not interested in folding or rolled panels). Often my wife will be putting this up alone, so 65 lbs is max for the battery (which can be mounted to a dolly system), but the panels could not be too heavy either. The Conergy P185M Monocrystalline 24 Volt Solar Panel has perfect dimensions and weight, but the question arises of all the differences in panels--which I guess is where my main questions lie. For the above array, 1) are there benefits to mono over poly (or vice versa), 2) is a 24 volt panel functional on a 12v system, 3) in addition to the panel and battery, do I need anything other than a charger and inverter--and which ones work best for this scenario? Any other advice or suggestions for this project would be most appreciated. Thank you in advance and I look forward to hearing from you and embarking on my first solar array.

Randolph Handel
Gainesville, FL 32609

Calculation Type/Description Units

1. Total Watts Per Hour (DC) DC Amps x 12 100 watts

2. Hours Equip is expected to run (24hr) 8 hours

3. Total daily usage--Watts x Hours 800.00 watts

4. Total watts Daily requirements 800.00 watts

5. Corrected for battery losses/static average loss 816 watts

6. System voltage DC voltage 12volts

7. Amp-hours per day Watts divided by Volts 68ah

8. # of days backup power required-24 hour periods 1 day

9. Amp-hour storage Amp-Hrs 68ah

10.Depth of discharge @ 50% 0.5

11.Required amp backup 136ah

12.Battery Amp Rating (20 hr) Battery Capacity in Amps 110ah

13.Actual # batteries wired in parallel Raw number 1.24

14.Batteries wired in series 1.00

15.Rounded number of Batteries 1

16.Sun hours per day 10 hours (optimistic)

17.Worst-weather multiplier* 1.55 1.55

18.Total sun hours per day Amp-Hrs 6.452ah

19.Select panel size (Watt rating) Watt hour rating 185 Watts

20.Nominal Panel Voltage - Approximate Solar output 16 volts

21.Amps required from solar panels--Total daily consumption 68 Amps

22.Peak amperage of solar panel – Watts/Volts 11.563 Amps

23.Number of solar panels in parallel-raw Number 0.912

24.Number of panels in series (12 V) 1

25.Rounded number of solar panels 1

Cariboocoot

Re: Portable Solar Light System Beginner Advice

Welcome to the forum.

Lots of data there! Let's see if we can simplify it a bit to make it easier to digest. Switching back and forth between Voltages and Amps and Watts tends to muddle things. So I'm going to ask some basic questions just so we're all on the same page.

1). The lights are how many Watts? Are they 120 VAC or 12 VDC? (LED's might easily be either)
2). There are how many lights?
3). The lights will be used for how many hours?

Once you get those numbers down you can figure: eight 10 Watt lights for 10 hours = 800 Watt hours.
That's a lot of power, actually.
Now convert it to 12 VDC: 800 / 12 = 67 Amp hours (This does not include system inefficiencies).
At 50% DOD that means at least 134 Amp hours of battery. This invariably will have to be rounded up to the nearest available capacity. Crown makes a 130, which just misses the mark.
From there you need to look at two recharging factors.
First is the current level. You try for 10% of the Amp hour capacity. In this case 13.4 Amps @ 14.4 (typical 12 Volt charging Voltage) or 193 Watts. That would be after derating, so probably 250 Watt array. Again you preferably round up to the nearest available size. This would likely be multiple panels too, as very large panels are difficult to manage and would be higher Voltage requiring MPPT charge controller.
Second is "replacing the Amp hours used". The theoretical 250 Watt array could reasonably expect to provide 500 Watt hours per day, so that's low for the expected 800 Watt hours use. Translation: more panels. And that's on a good day.

If this is going to be mobile you probably would want AGM batteries. Unfortunately they're more expensive, but safer to handle.

Frankly about the least expensive way of doing this would be three Kyocera 135's, a Prostar 30 PWM controller, and a set of 220 Amp hour 6 Volt "golf cart" batteries from your nearest warehouse store, and an inexpensive inverter.

Of course I could have completely misinterpreted everything in which case none of this is relevant except the formulas.