The goal is simple: Keep a volleyball court lit for a few extra hours after sundown so that we can keep playing!
The location is a park near a bar. There's no power to tap into, no existing light structure, and we can't leave it there. Which complicates things.
Here's the deal:
-Lights a fairly large area
I looked around online and priced the big items, quoted the group $400. People pitched in, it's officially started!
Shortly after placing the superbrightleds.com order for the two 27W LED lamps I noticed something strange on the website.. that the actual power draw was only 13W? This upset me a bit for two reasons.
1. My price comparison is bunk. Maybe I didn't select the best deal?
2. I could have bought less battery for my goal of 2 hour run time.
I fired up the tech support chat and.. well the guy tried to school me on how to calculate watts. I was not amused. The mystery went unsolved until I received the order.
Using a lab supply of decent enough accuracy I determined the power draw to be closer to 18W. OK, so that doesn't actually answer anything. But I can say that it's bright enough to turn my office into daylight.
At $50ea they weren't that cheap but so far I'm glad I went this route instead of trying to put together discrete LED's. There's a built-in constant current driver which accepts a large Vin range and a nice weatherproof housing..
When I got the battery I ran both lights from full charge till it quit. The rating is 10Ah / 128Wh, and it lasted 3.35hr. 128Wh/3.35h=38.2W (19.1W per light). That's a little higher than my measurement but in the right ballpark. You know how those battery ratings can be.
So, bad news is it's not quite as bright as I had planned on, good news is we have time for another 2 games.
Batt V started at 13.2V and drained to 12.7V and a fairly linear rate.
Spend some time on your LED and battery selection. These are the two most expensive items, and of course the most important.
In my case I'm trying to light a volleyball court. The light I'm considering is available in 30º spread or 60º spread. Also, the pole supplier offers 22ft or 32ft. I decided to mock this up in cad, which was pretty helpful in visualizing. I went with the shorter pole and higher spread.
I'm glad I did this because the pole turned out to be a bit flimsy, so it is likely we will not be putting it up all the way at 22ft.
About the battery.. I splurged a little bit with the Lithium. It was $160, almost half the entire budget. Here's why:
1. I really wanted to play with one of these batteries.
2. It will last more than 2 years before turning to shit. I want to believe that we are far enough into the future that this thing will still hold a charge in 10 years. That's way longer than my crappy tripod will last.
3. No acid to spill.
Small and lightweight are perks for sure but weren't main priorities. Plus this one has an undervoltage cutoff, so we can't brick it by leaving the lights on. Perfect.
When items arrive, pause your entire life to play with them.
Ok, the next part selection can fairly important depending on your taste, but in a pinch you could use anything. I've found this to be one of the best:
It's a seasonal though so good luck.
OK anyway, Digikey has a free online schematic drawing tool. I used it to draw this:
Pretty simple. For the fuse I used an automotive style with the fuseholder that has pigtails coming out. The relay and relay socket are from superbrightleds.com, R5-SW. So color code may vary. I picked a fun little switch with an LED indicator in it.
The cig lighter was an afterthought, I'm sure they draw more than 10A. It's just to charge a phone/radio. We blast tunes.