The end of daylight savings and no lights meant that 5:30 pm soccer practice would be totally dark. With field space severely limited this meant the end of practices. Next year we will be ready with portable battery powered field lighting, thanks to low cost, high power LEDs and lightweight long lasting lithium 36 volt battery packs from Dewalt.
I built two stadium lights. Placed on opposite sides of the field they do a nice job of lighting a decent size practice area for 10-12 kids. For a larger field or different sport, you may need several more. Each light draws ~.750 Amps, the Dewalt pack is good for 2.3 Amphours or not quite 3 hours. Still more than long enough for practice.
Needed 36 Volt Dewalt Lithium battery pack
These things are great, lightweight, fast charging, and very convenient after you have followed the directions to add standard power out wires. I will not detail how to disassemble the battery as this is readily available on the internet in several places.
http://www.slkelectronics.com/DeWalt/packs.htm
http://www.youtube.com/watch?v=qQJUEeKo7KQ
9 STAR LEDs (3 watts ~100 lumen each now available direct from China for around $2 per LED, ebay and other sources)
Most of these high power, high efficiency LEDs operate from 3.5 to 4.0 Volts. To save money we are not going to use the recommended constant current driver, but wire directly in series. (36 V / 9 LEDs) = 4.0 volts per LED.
CPU style heat sink
1 ohm, 10 watt resister (to add some safety margin)
18 inch long piece of aluminum angle (1/16" by 1 inch)
JB Weld Epoxy
1 inch hose clamp
10' x 1/2 pole (PVC pipe)
Screws, wire, solder
I built two stadium lights. Placed on opposite sides of the field they do a nice job of lighting a decent size practice area for 10-12 kids. For a larger field or different sport, you may need several more. Each light draws ~.750 Amps, the Dewalt pack is good for 2.3 Amphours or not quite 3 hours. Still more than long enough for practice.
Needed 36 Volt Dewalt Lithium battery pack
These things are great, lightweight, fast charging, and very convenient after you have followed the directions to add standard power out wires. I will not detail how to disassemble the battery as this is readily available on the internet in several places.
http://www.slkelectronics.com/DeWalt/packs.htm
http://www.youtube.com/watch?v=qQJUEeKo7KQ
9 STAR LEDs (3 watts ~100 lumen each now available direct from China for around $2 per LED, ebay and other sources)
Most of these high power, high efficiency LEDs operate from 3.5 to 4.0 Volts. To save money we are not going to use the recommended constant current driver, but wire directly in series. (36 V / 9 LEDs) = 4.0 volts per LED.
CPU style heat sink
1 ohm, 10 watt resister (to add some safety margin)
18 inch long piece of aluminum angle (1/16" by 1 inch)
JB Weld Epoxy
1 inch hose clamp
10' x 1/2 pole (PVC pipe)
Screws, wire, solder
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You have a bunch of really good questions. I will take a shot, one at a time.
Before you start down this path, can you get access to an electrical outlet? If the answer is yes then I recommend Keep It Simple (and cheap). It may not be elegant solution but if you have access to power, for an hour a day it will be nearly impossible to beat the lumen/dollar value from a set of electrical cords and halogen work lights. Go to Home Depot, Lowes, Amazon and get as many as you like.
http://www.amazon.com/Bayco-SL-1002-Halogen-Project-Light/dp/B000FW7UH4/ref=sr_1_3?ie=UTF8&qid=1346278571&sr=8-3&keywords=halogen+worklight
Mount these on tall poles and be done.
Because the world of LEDs this design now 3 years old and likely obsolete.
for the latest in LEDs and questions go here:
http://www.candlepowerforums.com/vb/content.php
for low price LEDs, search Ebay or here:
http://www.dealextreme.com/
how big a square feet or yard area do they light up?
With two sets of lights I lit 1/2 a youth size soccer practice field, roughly 30 yards by 30 yards. And for soccer low lighting is still "ok" as long as the players can see the ball fairly well. For a larger softball or baseball this you would need brighter (and higher lighting) and I would not recommend a low cost DIY approach. Use your best judgement.
about how much per light stand did they cost?
The light stands (LEDs, brackets, poles, wires, etc.) were around $30 total. Unfortunately the killer is the Dewalt 36 volt Lithium battery pack. Even on ebay these run between $90 and $120 each.
could I make it brighter if need to with a different battery and or light set up?
Absolutely. The easiest approach would be to simply to double, triple, or quadruple each light strip and add parallel connections to the power supply. More lights (or higher wattage LEDs = more lumens).
I have about $250 per light stand.
Should be doable.
Is it difficult to change out lights if burn out and do they last before burning out?
Yes. In the current configuration the LEDs are soldered in parallel. If one burns out the string goes down and you would have to desolder, twist off, resolder/epoxy. Fortunately the life listed for thees LEDs are 2,000 - 25,000 hours depending on power/heat. With one evening practice every day the LEDs might last between 5.5 - 50 years.
i have no experience doing this type of thing, is it not too difficult?
Jumping in and getting the experience is probably the biggest challenge. LEDs are fun, cheap, and simple. Get dirty, take chances. I do have one word of caution for the power supply. The Dewalt battery packs are portable, long life, light weight, fast charging great in many ways but.... they are somewhat pricey and when you open them to solder in a wire you have a high current source exposed. Please watch the video carefully.
http://www.youtube.com/watch?v=qQJUEeKo7KQ
Decide if you feel comfortable doing this. If this is your first electrical project I might recommend another power source. Perhaps three 12 volt lead acid batteries in series in a box or handtruck would be cheaper and easier to start.
As an example of how the LED world has changed in 3 years, dealextreme ( ~$67) is now selling a single LED module with an advertized output of an incredible 8000 lumen . One LED now has almost 10X the (8,000 vs the 900) light output of all nine LEDs shown in my instructable from above. (Of course you better mount that 8,000 lumen LED on a very good PC processor type heat sink, preferably one with a fan or liquid cooling).
Besides portability, does this device advantages over a low energy lamp connected to the mains?
I forgot to ask something that interests me more: are LEDs more expensive than equivalent "ordinary" lamps?
The one thing most agree on is that the standard cheap incandescents have lost. Go to Home Depot and on sale you can get a 60 watt incandescent bulb (claimed 15 lumen/watt = 900 lumens) for around $1. Plug it in for 24 hours a day and you will spend ~$52 of electricity. (60 * 365 *24 / 1000 watts/kilowatt) * 10 cents per kilowatt hour, about US avg. (total $53)
The el cheapo $2 LEDS I used are about twice as efficient, 33 lumens/watt. So 9*$2 = $18 but I would only use $24 of electricity per year. (total $42)
Gross simplification and does not include fixtures, AC/DC converter, converter efficiency, replacement bulbs, etc. But you get the idea. Invest now, save later.
Today florescent (up to 100 lumens/watt) easily beats both for most applications but are not robust for banging around as portable lights or smashed by an errant soccer ball. Cree/Seol/Nichia/Philips all claim to have next generation LEDS with efficiencies from 130 to 150 lumen/watt. And where LEDs may make sense today is if you are off-grid and already running DC power.