solar lighting for a shed

We have a new shed which doesn't have electrical running out to it. I want to setup some basic lighting in there. The commercial solar shed lights that I could find seemed to be pretty dim.

I already ordered a 15 watt solar panel and a charge controller to charge a 12 volt lead acid battery. Using a 7ah battery (normal for a UPS) I should be able to charge it in 1.5 to 2 winter Seattle days.

That gives me 85 watt hours to play with, which is more than enough for some bright LED lighting. The shed is 8x6' of floor area.

I haven't had much luck finding the lighting that I imagined. I see two options, and wanted to get some feedback on them:
1) String together ~10 1 watt LEDs and arrange them in a U shape around the perimeter of the ceiling. I'd probably drive them with the maxFlex driver configured for 350ma.
2) Use some of the LED light bars that are out there. It is difficult to find ones that run on 10-12V (most are designed for 12-24V) and few of them have useful specifications on brightness and power consumption.

So my questions are:
1) What is a good source for inexpensive LEDs? My only care is star mounted. I'm not that picky on efficiency (I don't need Q5 CREE). Can I get the price down to $2-$3 per LED by going for lower bins?
2) Are there light bars that I'm missing (I've checked eBay and DealExtreme) which would work well in this setup? The ElaraStrip from LEDSupply.com looks pretty nice except for requiring 12V+. I'd like something that can run on 11V to keep working as the battery runs down.
3) Is there a cheaper/better driver for this setup than the maxFlex? $45 is a bit on the steep side. A great feature would be having an automatic shutoff timer that is configurable, but if one isn't available I can build that circuit easily.

alex

Have you considered getting an inverter? For $30-50 you could covert your 12v DC to a 120V AC plug. Then you can run a couple nice T8 LED tubes or par bulbs to light up your shed.

Congrats on such a cool project! I suggest LED Supply for the LEDS.
Depending on how much and how close you need a light source there are many options. If you need looooooong term minimun visability, run a single 5mm-10mm LED, or a few then add white walls and ceiling and you will never be in the dark again! For higher brightness LEDS, you will need adequate power storage.

holiday light express said:

Have you considered getting an inverter? For $30-50 you could covert your 12v DC to a 120V AC plug. Then you can run a couple nice T8 LED tubes or par bulbs to light up your shed.

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I have, but it seems much more efficient to keep everything on 12 volt. The cost of an inverter ($30), a good (electronic ballast, reliable in cold) T8 fixture ($40), 2 T8 bulbs, and a timer switch ($20) is not much different than the cost of 10 1W LEDs ($40), a driver ($40), and building my own timer switch (free to $10).

alex

tsask said:

Congrats on such a cool project! I suggest LED Supply for the LEDS.
Depending on how much and how close you need a light source there many options. If you need looooooong term minimun visability, run a single 5mm-10mm LED, or a few then add white walls and ceiling and you will never be in the dark again! For higher brightness LEDS, you will need adequate power storage.

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I think my power storage is more than enough. A 12v/7AH battery is good for 84 watt hours. 10 1W LEDs plus a 80% efficient driver is about 12 watts of consumption, so that is 7 hours of light. Our maximum target usage would be 2-3 hours per day, so that is a lot of surplus.

I am curious about lots of low power LEDs (strip lighting) vs a smaller number of high power LEDs. I don't know the efficiency of the smaller LEDs. Am I better off with 10 30ma LEDs (consuming 1.6 watts total) or 1 high power LEDs with a difuser in terms of efficiency?

alex

Alex Wetmore said:

I think my power storage is more than enough. A 12v/7AH battery is good for 84 watt hours. 10 1W LEDs plus a 80% efficient driver is about 12 watts of consumption, so that is 7 hours of light. Our maximum target usage would be 2-3 hours per day, so that is a lot of surplus.

I am curious about lots of low power LEDs (strip lighting) vs a smaller number of high power LEDs. I don't know the efficiency of the smaller LEDs. Am I better off with 10 30ma LEDs (consuming 1.6 watts total) or 1 high power LEDs with a difuser in terms of efficiency?

alex

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A 1 watt high power LED will most likely be brighter and will definitely last longer than 5-10mm LEDs.

What about using 2 12V batteries in series = 24V?

jason 77 said:

What about using 2 12V batteries in series = 24V?

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Is charging in parallel and discharging in serial a good idea? It would be more difficult, but it is feasible. It doesn't seem like a great idea since the batteries could discharge at different rates.

The solar panel puts out 15 volts and the charge controller is designed for 12 volt batteries. Buying another panel and charge controller isn't an option (at least if I stick with my original budget).

alex

jason 77 said:

What about using 2 12V batteries in series = 24V?

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that would require a completely different charge controller plus the possibility in the increase in charge time assuming that he sticks to a 15W panel

Your current system is not much different than what I am currently using - and have been using - for almost 2 years now.

I have a 21-watt solar panel, PWM charge controller - and 12V/17Ah SLA battery.

I have - hooked to that - a LVD (Low Voltage Detect) pcb (that I designed), and 3 - 5 Watt LED MR-16 'bulbs'.

The light from these - is about 150 Lumens * 3 = 450 Lumens.

It is very adequate for lighting our living room - and part of the kitchen/dining room in the evenings.

I also have another LED lighting system outside - using 4 1-watt Amber LEDs - for my front porch light. They are 4 LEDs on about an 18-inch strip. Again - adequate light to see while coming up to the porch. The solar panel for these is about 10-watts, and the battery is about 7Ah.


For your application - go with the 1-watt LEDs - run them at about 350mA. If you use a Constant Current controller - you could run up to 6 of these 1-watt LEDs in series. This would be qute a lot of light for a small shed.

Sounds like a fun project!

Regards,

James Jackson

I finished this project and thought I'd link to it in case others are interested in similar projects:
http://blogs.phred.org/blogs/alex_wetmore/archive/2009/04/02/solar-led-shed-lighting.aspx

I'm pretty happy with the final result.

Alex Wetmore said:

I finished this project and thought I'd link to it in case others are interested in similar projects:
http://blogs.phred.org/blogs/alex_wetmore/archive/2009/04/02/solar-led-shed-lighting.aspx

I'm pretty happy with the final result.

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Nice work Alex. Thanks for coming back a month later to follow up.

Yep,Great job Alex.:thumbsup:

Thanks for the update.Very interesting.

Very nice project! If you ever decide to add more panels to upgrade the system, you could use a 12 volt gel cell battery or a couple of 6 volt golf cart batteries.

hi - i did a similar thing about a year ago mine isnt as "finished" as yours but it works

im in the uk and there is less sun but i opted for a system that wouldnt need a controller and had a bigger battery

im using a 12v 12a battery and a 2w panel i think or it might be 5w anyway it is low enough that it cant really over charge a battery of that size - just trickle charges it in the small amount of sunlight we get

same as you 8x6 shed but i have 3leds mounted on a heatsink with fan
no driver just 11-12.8v going to 3leds but with that fan on it dosnt even get warm i dont think the battery is ever full so each led is getting max 4v but its probably less by the heat im guessing less than 3.7v but i should be getting about 500 - 600 lumens

ill take some pics and post them

eventually im going to strip mount it like you and use a driver

the charger without controller keeps the batter topped up and ive had it on for a few hrs sometimes without it fading

good job on your light

looked at your link and its quite strange how my name is alex im refurbing my kitchen in a cherry style im into steel frames bikes etc etc