Solar Powered Light (LED) with Charge Capability

Just out of curiosity, how is the inside of the box finished? Painting it white should help illuminate the interior and make it appear brighter.

I've been using solar panels, battery bank and invertor for about 9 years as 100% of my power source for my house, so I bet I could help you but I would need to know what the panel output DC power is, what batteries you have, and what's the total wattage of your LEDs? Are you running DC or AC LEDs? If they are AC, what's the size of your invertor? Also, yes you would want a charge controller, if your panel is more than a trickle (mili-amp) output. You can also purchase DC compact light bulbs too, much more lumens with not much more power needed. DC light bulbs are available at most solar supply companies, if you want my rec on my fave company let me know.

When you say 'light bulb', to me that implies incandescent lamps. Virtually all white LEDs are WAAAAY more efficient ( in producing light) than incandescent lamps using the same amount of power. I just replaced a 150 W incandescent with a 5 W LED lamp, and am happy with the results.

The lamps I have on hand still in packages so I can read their properties:

Incandescent: 40W gives 400 Lumens, or 10 Lumens per Watt.

Compact Fluorescent: 13 W gives 900 Lumens, or 69 Lumens per Watt.

Compact Fluorescent: 23 W gives 1600 Lumens, or 70 Lumens per Watt.

LED: 3.5W gives 172 lumens, or 49 Lumens per Watt.

I have found the CFLs quite satisfactory in places where no one can reach them, but they are quite fragile - I have accidentally broken at least 5 over the last decade (liberating a minuscule amount of mercury).

Time will tell how durable the LED lamps turn out to be, but I just checked: all the LEDs still work in my 30-something year old calculator. Obviously they haven't been on all those years, so it's not quite a fair comparison. Not too long ago I took apart a red LED traffic light where quite a few of the LEDs were out. In every case, the LEDs were still good; they failed due to poor solder connections to the circuit board.

I meant CFL bulb, I call them light bulbs. I don't use incands for anything anymore. Most boxed signs use FL lighting, so it seems a good try would be to go CFL, but as your chart points out, the wattage required for LEDs is far less so they might be the best in a 3.6v scenario.

At 3.6 V, there is almost no question. LEDs are low voltage devices; all you need is a current limiter of one form or another, and they can be driven directly. In fact there are quite a few White LEDs available that are rated 3.6V. You need to check the particular LED, but some of these may even contain integral current limitation, so they could be connected directly to the battery (with a fuse for safety, of course).

Fluorescents (including CFLs) require much higher voltage, and therefore an inverter to operate.

As hioptemp stated, when operated from 120V, CFLs are, (so far - they keep improving both types), more efficient than LEDs, but to operate CFLs from 3.6V, you're going to need 2 inverters, one to step up the 3.6 to 120V, and the already existing one in the base of the CFL. I'm virtually certain that second inverter is going to kill the efficiency advantage for CFLs.

Your table indicates that CFL is the most efficient.

Therefore an inverter is called for to step up and oscillate (not necessarily in that order) the solar panel power.

CCFL is 1.4 times better than LED

Fragility is not an issue in a box.

this is 60 lumens/watt:

http://www.bulbs.com/eSpec.aspx?ID=8216&Ref=T-12+U-Bent&RefId=57&Ref2=Fluorescent+Bulbs

DC ballast here:

http://www.oksolar.com/lighting/ballasts.htm

Check battery amp-hours and multiply by voltage, then divide by lamp wattage ... = run time.

charge rate is weather variable.

done

(BRAIN RUN TIME= 148.3 secs)

White paint is a great idea. I was also going to put a mirror along the back wall to allow for more reflection.

I am going to find out more about the solar panel from the manufacturer.

The LED's are DC (there is no invertor), and I want everything to run off batteries. The unit itself comes with 8 Watt Fluorescent light and 3.6V Ni-CD AA 600mAh rechargeable batteries.

I can get any other type of rechargeable batteries from Ebay, they range in mAH and quantity per pack. Would they need to be Ni-CD or can they be Ni-Mh?

I could also go out and purchase more LED's and splice them into the circuit.

not paint, nor mirror, but bright tin foil. the type the missus uses in wrapping cooked food.

lightweight, non-toxic, unbreakable.

having been in the signage business myself, I would use colored acrylic, not colored glass. acrylic disperses light better, and is less breakable than glass.

Regards.

Modern Reflectors are are also lightweight, non-toxic, unbreakable and cheaper while the wrap ???

You know the hand flash-lights' have.

You have to work a lot to do any good reflection; with lts ot wrinkles on relecting surface.

reflectors are breakable.

the wrap is superior to modern reflectors in terms of handling (very light), formability (fits in any shape) and more importantly, cost.

I agree you may create some wrinkles during installation, but that doesn't matter because the acrylic is already a light dispersant. the more dispersed the light source is (from the foil's reflection), the better. and you don't need a focused beam of light on it. trust me, you won't appreciate an uneven lighting inside a signage, as it creates unsightly dark spots.

Regards.

I fully agree & add are much cheaper.

To have straight one is quite easy, but if any other profile it may be a little difficult.

Regards.

<< White paint is a great idea >>

Why not the manufactured item with properly desined reflector; like Hand-Flash-Light; is purchased ?

Look for an LED-Emergency Light. units with Flouro tubes are less efficient as using an inverter & less reliable due to it.

Good idea to splice in more LEDs then, and you can add another one or two 3.6V batts, keeping them in parallel not series so you don't change your voltage to the lights. You can add more batteries and it will just take longer to charge them if you don't increase the panel size, you do still need to findout what the panel output is to protect from overcharging. Let me know what the output is, I'll check back in a few days.

Hay guest:

Consider building a joule thief (Google it). You can use a single 1.2 volt cell and parallel a hundred bright white led's off of it.

If you so desire, purchase a six-pack of solar walkway lights for around 10-15 dollars. Cut the led off of one and leave the two legs. Hook the joule thief to the legs, hook up your led's to the joule thief and you will accomplish your goal.

Buy a bunch of individual LEDs. Drill a series of holes, the same diameter as the LEDs, in the pattern of the outline of the logo but a little smaller, in a thin sheet of plastic or plywood that will fit in the box. Place one LED in each hole, and depending on the voltage of your battery and the forward voltage of the LEDs, wire the LEDs in series sets with an appropriate resistor for each set to limit the current, and wire all the series sets in parallel through a switch to the battery. Set this unit behind your translucent logo cutout, and you've got it!

for the OP's purpose (a cut-out signage), the ideal application would be neon light behind the acrylic. but his is a special project, using lights with charge capability, i.e., a solar panel to make it portable, and independent of any power source. the LED is the best light source for it. his problem is that the light seems insufficient and would like to add more LED lamps.

from a practical viewpoint, a simple reflector such as a tin foil can help in "amplifying" and dispersing light in addition to the increased number of lamps. the use of colored acrylic will be superior to colored glass since acrylic disperses light better and thus will appear brighter and gives no dark spots, considering the lamps are not too close to the acrylic that the individual lamps can be seen, unless, of course, that is the effect he would like to achieve!

there is also no need the lights to be formed exactly like the logo (that makes the signage more expensive). the important thing is that the lamps are spaced fairly equally from each other and spaced correctly from the acrylic, so that there is no dark spot. the OP would be in a very good position to determine this, because this depends of the brightness of the lamp, and the size of the logo to be backlighted.

good luck on your project!

Regards.

The link does not give any technical details about its construction or shape ...

Nothing can be said

LED is good if it is well ventilated. this is among the few downsides to using LED signs, the lights being sensitive to temperature and voltage. otherwise, good old flourescent or CFL might be your option. of course, you might be able to find LEDs that can work for extended periods in enclosed spaces without any problem, then that would be good, too.

why don't you use tarpaulin or panaflex as your medium for the cut-out instead of glass or even acrylic? that'll make the signage even lighter.

Thanks to everyone's input!

Additional information regarding the solar panel from the manufacturer - produces 7-8 volt in ideal conditions

In regards to the design, it will be roughly a 2.5ft x 1ft design, with 6" depth. Made of reclaimed wood.

The front will have a logo cut out, and inside the box, on the front will be a sheet of glass or acrylic. Behind that, will be the lighting assembly. I will use foil throughout as I agree it will disperse the light better as a mirror creates too much of a focused light.

The reason I first wanted to go with a colored glass is because of the specific color I require: turquoise. which I could only find in a glass. Also, the glass is not see through. I agree, there is a concern that it can easily break. I didn't want to use a plastic because I am trying to keep this as sustainable as possible.

With a charge capability of the solar panel, how many rechargeable batteries could I hook up to it? Is there limitations on the types of rechargeable batteries?

You didn't specify the current output of the solar panel, so we can't say how large a battery (or how long it will take to charge it/them). 7-8 Volts is barely enough voltage to charge 2-3.6V batteries in series, with no protective diodes. In less than ideal conditions, it wouldn't fully charge them.

What is the expected duty cycle (how long to charge, and how long do you need the lights to last each use)? If there is light (from other sources) on the solar cell during use, the output of the solar cell can reduce the current that the battery must supply, and thereby extend the duration of the battery.

A couple of limitations on the types of rechargeable batteries:

1. NEVER mix batteries of different chemistry! eg. some NimH and some NiCd.

2. All cells should be the same size, the same age (don't mix old ones with new ones), and ideally from the same production batch (buy them all at the same time).

This a good site for superbright LEDs: https://www.superbrightleds.com/led_prods.htm