Billboard night flood project

[Prinler]

I was approached by a customer of mine to help him light up a 28' box truck on the side of a highway. I have many used solar panels and 2 nice new solar batteries capable of 100ah each. I have never been good at setting up the math involved and i need your help.

I want to use 2 of these


2 lights
1 dusk to dawn switch
1 100ah battery (thats what i have laying around new)
1 solar controller
X solar panels....

How many amps worth of 12 volt solar power will i need to ensure the battery fills up every day of 12 hour nights (worst case)?

[Sunking]

Not enough info to answer. 2 lights are meaningless without wattage, location, and time of year use.

[Prinler]

ebay URL Deleted by Mod.

Item # on ebay 120586540314

Mod note: While linking to ebay isn't a "bad" thing, it's a good idea, poorly executed. What happens, is that in 2 weeks, the link becomes invalid, and is archived here, as a broken link. Listing an item #, or the name of the thing, works better in the long term, as folks now, and in the future, can locate more than the ebay Page 404 Not Found message.
198 LEDs flood light 12VDC 12W waterproof Alum Case

[Mike90250]

24 watts of light for 12 hours dark = 288watt hours

Morningstar makes a charge controller, that has a dusk-dawn lighting feature:
Morningstar Sunlight Solar Lighting Charge Controller 20 amp, 12 volt PWM

http://www.solar-electric.com/sunsolligcon1.html

(they also have a 10A version for a few $ less, but I'd suggest the 20A)

288 wh /12V = 24ah consumed. To account for losses, your system needs to harvest twice as much, in 4.5 hours of useful solar light. That would be 576wh, /4.5 gives you a 128w panel needed. To be safe, I'd use a 135W or maybe slightly larger. @ 15v , that's 9a at solar noon.

The question is, will the aforementioned LED lamps, be bright enough ? For a large truck, I'd think 6 lights, slightly staggered, 3 top, 3 below, would be the minimum . LED lights are very directional, and don't have good beam spread.

That would then need 3 PV panels, and an aux * controller to assist the Sunlight Controller. It would only last 1 night on the battery, depleting it 75%, which will shorten the battery lifetime.

* Parallel with a SunSaver for 40 amps solar • Includes SunSaver battery charging circuit

[Prinler]

Thank you Mike for your reply. Thats what i was looking for. You don't think 2200 lumen's will light up the side of this truck well? on the auction for the light it shows a really nice bright illumination of the roll up door. I guess there is no way to really know. Only safe way would be to over design it like you mentioned at the end.


I'm gonna have to figure out how many watts my solar panels put out. (this is where i'm trying to make money and save him some)

voltage * amps = watts right?

When connecting multiple solar panels together do i need to use shotkey diods? to separate each panel? Keep it all flowing in one direction? Or will it do that naturaly?

[Mike90250]

solar panels should have a sticker on the backside, that indicate their Vmax power, Imax power, Voc Vsc

or, you can measure open circuit voltage, short circuit amp, , multiply, and deduct 20-30%, and that will be close. Vmax power does not occur at Voc.

To connect panels in parallel, 2 are fine, but when you add the third in parallel, you need to install a fuse at the labeled value to prevent a fire, if one panel fails, 2 or more can source enough current to cause a fire.

[Prinler]

Ok well per my
OTHER POST.

Is 16V, 20A, 320W enough to charge 2 100AH batts to full per our above posts...
2 lights = 24 watts of light for 12 hours dark = 288wh
4 lights = 48 watts of light for 12 hours dark = 576wh
6 lights = 72 watts of light for 12 hours dark = 864wh

2 lights = 288 wh /12V = 24ah consumed
4 lights = 576 wh /12v = 48ah consumed
6 lights = 864 wh /12v = 72ah consumed

2 lights = 576wh, /4.5 gives you a 128w needed
4 lights = 1152wh /4.5 gives you a 256w needed
6 lights = 1728wh /4.5 gives you a 384w needed

So if i did that right.... With the amount my panels put out... accounting for dirt and bird poo... I think 4 lights would be ok.

What do you think?

Would a 30A controller be needed? Or just a 20A? Im thinking if in perfect sun it goes over 20A like 21A i could fry the controller right?
Ebay auction 260771266590
TEKTRUM 30A 12V/24V SOLAR PANEL CHARGE CONTROLLER WITH LCD DISPLAY

Just to confirm, im going to hook the lights up directly to the batteries right? or threw the "LOAD" side of the controller? whats going to give me best results?

[Mike90250]

I really don't like buying ebay parts for "critical" systems, as you have no real recourse.

The LOAD terminals on controllers has a stated power limit, or you burn the controller up.

I like the morningstar Sunlight controller, because it is made for lighting, but I don't know what happens if you exceed the current limit. Nothing really good I suspect. You could aim the PV array with PWM controllers, so they both don't align with the sun at noon, set one for 11am, and the other array for 1PM, and your peak charge rate will be lower, but a longer high rate will be seen by the batteries from 10am- 2pm.