12V Solar setup powering cree xp-e's

[mcoski]

I'm looking for help figuring out what size battery and solar panel setup would be sufficient for my needs.

Requirements:
-Reliable/weatherproof LED setup to light area from 25-100 yards out.
-Affordable solar panel setup with battery
-RED

Here's what I have as possible components for this setup:

-Battery: I have a 12V 18Ah/20hr AGM battery taken from a portable car jumper. From my research this battery type is perfect for solar setups.

What I'd eventually like to find is the minimum requirements for a battery to power this system. (6v possible? less Ah? etc.)

-LED: Must be red or green and project so figured the cree xp-e's would be good. From www.ledsupply.com I found the 3-up red's might fit the bill. If there are other suggestions please let me know.

-Driver: I plan to use a puck to drive them at 700mA each. According to the website and my calcs thats 6 LED's at 700mA = 4200mA = 4.2A. The Vf for the LEDs would be 13.8V (6 * 2.3Vf). Not sure if these calcs are wrong, please correct me if I am.

-Heatsink/Housing: Might use the ones shown on ledsupply's website, but may machine/find my own. I do like how their setup just screws into normal junction boxes, would be easier to fabricate the enclosure when done.

-Solar Panel: 12V 5W should be sufficient? Overkill? Got a little lost doing the calcs for this but here is some info. Will be using a dusk-dawn switch so run time on the lights will be ~9hrs each day. The solar panel will be getting ~10-14hrs of sunlight a day (Texas summer). But I suppose using the low end would be better ~10.

So here are my a few of my questions:

1) Can someone show me the calculations to show my power usage per hour and how that translate to picking a battery and solar panel setup?

2) Is my current battery (12V 18Ah/20hr) sufficient for (2) 3-up cree xp-e driven in either 350mA or 700mA (calcs for both?)?

3) Would driving the LED's in 350mA be sufficient for my requirements? Up to 150 yards (rated 137 lumens @ 350mA * 2 = 274)?

4) Whats the smallest battery requirements (SLA/AGM/etc) thats cost effective to drive the setup at 350mA and 700mA?

5) Whats the smallest solar panel I could get by for 350mA and 700mA?

I know lots to read...Thanks!

 

[Steve K]

interesting problem, and will definitely benefit from some number crunching. Need to figure how much energy the LEDs will draw, how long they will run, convert that to energy (joules = watts x seconds, or just stick with watt-hours, since that's easy to convert to amp-hours that are used to rate battery capacity), and then use some worst-case assumptions to figure out what size solar panel you'll need.

I'd throw in some estimates of power losses, such as a 20% loss in the buck converters that drive the LEDs. Also assume some charging losses in the battery (10%??).

Solar panel power depends on soooo many things.. temperature, how bright the sun is, the angle of the solar panel relative to the sun (i.e. is it pointed right at it?), etc. It might be most cost effective to just have a low voltage shut-off circuit for the LEDs so you don't drain the battery too far.

Anyway, my big question is: why red and green LEDs?? Are you making navigation lights for your boat or plane?

If you're not in a hurry, I think I'd start by buying some LEDs and drivers, and seeing exactly how many LEDs are needed. Once you get that figured out, you can play around with batteries and see how big it needs to be. That should give you enough data and experience to know how much power you'll be drawing out of it, and that'll be a guide to what size solar panel you'll need.

have fun. 🙂

Steve K.

 

[Microa]

Have a look at this thread. http://www.redrok.com/main.htm
This guy is an expert who may answer your questions.

 

[deadrx7conv]

dusk to dawn setup? or remote control, or motion sensor? what country/state for solar power? for camera usage? why red or green LED?

I'm not sure how you're going to light an area with red or green to 100 yards.
I'm using a 50w cool-white LED for my 100-yard driveway and its effective and adequate but nothing to brag about.

Also, you'll have to trial&error your battery:solar size depending on how long you want to run the light each night. My dusk/dawn lights seem to work perfect in the 3x-5x batterypanel:led ratio range. Example: at 12v, for each 1w of LED you'll need at least 3-5 watts of solar panel, and 3-5ah of battery capacity. So, with that 18ah AGM battery, I'd aim for a 3.5-6w LED(smaller is better) and 18w(bigger is better) solar panel(20w panel and 2 watts loss to charge controller).

The biggest problem with outdoor solar lighting is underestimating solar panel and battery capacity. And, too many overestimate the sun and efficiency of an LED.

This thread is a good read on how to use the leds in series with the driver(powering an LED) in order to use the cheapo amc7135 driver with higher voltage batteries:
http://www.candlepowerforums.com/vb/showthread.php?201392-Poorman-Mutli-Lux-setup-method A 700mah 7135 driver is cheap and should power 5 LEDs(4 in series to the driver and one off the driver) from your 12v+ battery.

Also, there are 10w and 20w red/green/blue/white/warm.... LEDS on ebay, some star mounted. For example: http://cgi.ebay.com/400224620740 or http://cgi.ebay.com/400224620749 Since LEDs can usually underdrive to 1/5-1/3rd their rating, you can start out at lower wattages and increase as needed to find out how much lumen you need.

If you want a simple red LED test light powered by your AGM battery, visit the auto salvage yard. Various vehicles have 3rd brake lights and regular brake lights in LED. And, red LED trailer lights, hitch lights, accent lights, 3rd brake lights..... can be found on ebay and at auto parts and department stores for $25.

 

[purduephotog]

Go boost.

There are boost drivers that can take you 12V up to whatever voltage you need. Doing this ensures you won't have to waste energy but still permits decent string length without going parallel.

Do each string independent.

Good luck.

If you are REALLY cheap then check out DX for some 18V flashlight boost circuits- about 4$ a piece- and can control 6? LEDs.

 

[mcoski]

Ok, thank you all for the suggestions/comments so far. I'll try to answer them as I can.

@SteveK: I do believe this project will be fun. I was given some parameters from a friend to build him something for his hunting. I figured at worst I can get most of the parts from the web rather than machining any parts needed for the project. So red + green for the animals is the reason.

@Microa: I think you just unleashed a can of worms in my head.

@deadrx7conv: I'm going to be using a dusk-to-dawn switch as stated in the 1st post. I gave some rough estimates on hours of usage and possible charge time as according to recent data of "day length" for Texas summers.

I found the 3-up LED's http://www.ledsupply.com/creexpe-red-3.php. That's ~137 lumens @ 350mA. Two of these should have zero problem hitting that distance if I'm not mistaken. I think trial and erroring battery/solar panel size is going to be WAY too costly/inefficient. I think we can find an answer to a problem using these parameters:

Lights: (2) 3 - up CREE XP-E Red LED's. http://www.ledsupply.com/creexpe-red-3.php
Driver: (1) 350mA microBuck http://www.ledsupply.com/bucktoot.php <= sufficient for this being driven by either a 6v or 12v battery?

Usage per day: 9 hours

Just given that is the calc: 6 * .35 = 2.1A (I'm assuming this is per hour). or 18.9 over the 9 hour stretch.

Watts = Volts x Amps

Below are numbers for each setup (before other factors):
(6V) Watt/hr: 12.6 Total Watt/Day: 113.4 Ah: 18.9
(12V) Watt/hr: 25.2 Total Watt/Day: 226.8 Ah: 18.9

Does this mean regardless of 6V or 12V the Ah required of the battery in terms of storage is 18.9 w/o decay/etc? And w/o the help of solar yet.

Let's see where we get from here, my mind hurts :duh2: and I think I'm over thinking this.

 

[deadrx7conv]

You need to look at a solar map for your zip code or your GPS coordinates. Texas has 3 difference solar zones depending on location. Don't confuse sunrise:sunset time with actual solar capable time. Your panel will have a power curve, and unless its is tracking perfectly for your location, will only produce peak power for a short period of time. More than likely, a small panel will be fixed mounted(angles adjusted monthly if you're ambitious) and make about 1/4-3/4 of what we wish that it can produce(or its rating). Or if you're really really ambitious, you can manual adjust the solar panel angle every 15 minutes to get some good charging power out of it.

Your battery won't last too long if you run it down to zero(<12v) every day. How often do you want to replace the battery? So, I wouldn't use a 18ah battery for more than 1/3-1/2 its rating. That 18ah battery is a reliable 9ah, and a really long life long lasting 6ah battery.

Formulas on paper are great. But, in the real world, your inefficiencies and over expectations will kill you. This is why fixed calculations that you want are meaningless. The real world puts textbook formulas to shame. Your dusk:dawn sensor uses how much power? your driver wastes how much power? your solar charger is how efficient? your battery power available and life when discharged to 50%? or 75%? your wiring runs/connections resist how much power? of course solar inefficiency since dusk:dawn time means nothing? mppt vs pwm charge controller?

You also need a couple extra volts for a buck driver. So, grab 2 of those bucktoot drivers and use one to power each 3x star of 6.9v of series LEDs.

3x-5x of battery amps and solar panel watts for the given voltage(12v) for each watt of LED is a good starting point.

2 of those bucktoot drivers, with each 3xLED board independent. That will be 2.5-3watts per board for a total of ~6watts. 6watts of LED x3 or up to x5 requires 18ah to 30ah of battery, and 18w-30w of solar power. IMO, your battery is border line and won't have a long life. Get a bigger battery. Your free battery is a limitation to whatever you want to do. I would get at least a 30w solar panel. This way, you'll have extra power for additional time or reserve(short sunny days/clouds/shadows...), and extra power to make up for fixed mounting/poor aiming. And, a cheap PWM charger controller(with dusk/dawn and low voltage cutoff will work fine). But, if your battery and panel or border-sized inadequate, you can squeeze out a little more charge with a MPPT charge/controller.

Your battery produces 11-13.2 volts depending on charge and temperature. If you want to run all 6 LED(13.8v) in series, you should email taskled.com and see if one of their fancier LED drivers would be better. Maxflex6? This way, if 350ma isn't enough, all you have to do is tell the driver to run at 500ma or 700ma. And, if you run it at 700ma, you can program it to 500ma or 350ma if the battery voltage drops off.

I use a poorly mounted(landscape hidden) 125w solar panel, a 125ah battery, and 30w LED all year round with no problem. My "LED times 3 to 5" formula works fine since it gives me a 90w-150w solar panel range and 90ah-150ah battery range. I have to use more battery and tilt my panel(making it noticeable) when I run the 50w LED. My dusk:dawn is about 8hrs now but closer to 15hrs in the winter. I just picked up 2 more 80w LED flood lights. That's 160 more watts of LED((70w LED plus 10w driver) x2). I'm looking at 700w solar and 700ah of battery power to use these new lights together. I really would like my new 160w lights to work with less panels(they get expensive) and less batterie$. So, with the clouds here, MPPT along with CIS/CIGS or amorphous might work better with my mounting angles, clouds, shade, pollen,..... I might start with 400w solar and 400ah battery and see how it goes. These used 80w LED lights were someone else's failed solar project. When I told them that they needed 3x to 5x as much solar watt and battery amp to be usable with that 160w of LED power, I got the 'deer in the headlight' look because the 'formula said' and the 'consultant said'.... I guess that my world isn't that perfect.

Since I can't see what you can see, I can't say whether 3w, 6w, 9w, 12w.... of red LEDs would give you enough 100yard lumen for what your night plans are. This is something you will have to test yourself, along with your panel size, battery choice, LED..... Quit worrying about the formulas.

 

[mcoski]

@deadrx7conv: Thanks so far, your info has been great. The reason I'm worried about formulas is that the budget that I'm working with is limited. If I can find the smallest/minimal battery and smallest solar panel I could possibly work with then hopefully I can stay below budget (~120$). But you are right, real world conditions will tell me everything, I'm just trying to get closer to an answer.

I'm tired so I'll do research on the solar zones tomorrow as well as.

Before I head to bed can you guys tell me if this is correct. With the 3UP Led having a Vf of ~6.3 per star. Would you use that in the formula: watts = volts * amp. Giving you watts = 6.3 * .350 = 2.205 per star? As you said add a little for the buck driver giving ~6W system?

Therefore 9 hrs * 6W = 54Wh / 12V = 4.5Ah.

This is the end "baseline" consumption of the two 3UP stars, correct?
If perfect world conditions allowed for 10hrs of charging with a 12V 5W panel, you'd use the same equation and say 54Wh/10hrs = 5.4W panel needed?

And is Vf how many Volts the LED eventually consumes per hour?

Tons more questions...thanks!

 

[Microa]

The above mentioned link contains a lot of solar power resources. Such as, U.S. Solar Radiation Resource Maps, Shunt Charge Controller, Under Voltage Protection etc. Almost everything related to solar power you can find there.

You are right for the LED part. Vf * Iled = Wled. However, the LED requires a driver which has power loss. The solar panel charges the battery also has power loss.