A few years back, we installed a sun shade sail in our backyard. We love having the shade (check out the sun shade sail DIY), but we always wanted to turn the wooden posts into something more.
I’ve always been fascinated with solar power, for the environmental benefits and it’s a direction to move off the electrical grid. It’s a great feeling knowing you can generate electricity from something natural.
So I figured the shade sail posts could serve a dual purpose – anchoring the sun shade sail and providing solar power lighting.
It was perfect timing for our monthly DIY challenges. We are collaborating with a lot of talented DIYers to share themed projects, and this month’s theme is to fix up something outdoors. Last month, the theme was home improvement and we redid our pantry with new shelves and drawers and wallpaper.
Be sure to scroll to the end of the post to check out everyone’s outdoor projects.
DIY Solar Power Lights
There are usually four parts to most solar powered projects – solar panel, battery, charge controller and load (such as a light bulb).
A solar panel produces electricity from the sun, and charges up a battery.
The battery is then used to power electrical things like light bulbs.
A charge controller is needed so that the solar panels do not over-charge the battery and damage it.
Solar panels come in many different wattage, depending on how much power you want to generate.
To decide on a wattage that was appropriate for me, I had to think about what I wanted to accomplish. I really just wanted some lights in the back yard that turned on automatically at night, and remained on for a certain amount of hours.
There are many solar lights you can purchase from the store that do something similar.
However, they are usually motion activated, not very bright and don’t usually stay on for hours.
Choosing a battery
To build my setup, I needed to power my light bulbs with a decent sized battery.
I opted for a 20ah deep cycle battery, which I calculated would provide enough electricity to power several bright 12 volt light bulbs all night long.
These batteries are similar to your average automotive battery, except about 1/3 the size, and designed specifically for powering devices over a long period of time.
Deciding on a Solar Panel Wattage
Now that I’ve decided on a battery size, I needed to come up with a wattage for my solar panels.
I needed a solar panel powerful enough to fully charge the battery during the day so that the lights would be operational at night time. I settled on a 100 watt solar panel.
Getting a solar panel charge controller
For the solar panel charge controller, I didn’t need anything fancy. I just choose a cheap one with good online reviews. It was important that it had a timer though, so the lights could turn on and off automatically.
LED Light Bulbs and Lamp Fixture
LED light bulbs are a requirement for almost any solar powered project.
Incandescent light bulbs (and many other types) suck up way too much electricity to be powered practically by a battery. I searched around for 12 volt LED light bulbs and settled on some fairly bright ones (7 watt ones, equivalent to a 60 watt incandescent bulb).
12 volt bulbs were needed as the battery was a 12 volt battery.
Most LED light bulbs used around the home are 120 volt bulbs, and would not be compatible with my solar powered project.
I also needed an exterior lamp fixture to install the light bulbs into. I found some nice 12 inch globe fixtures online that would be perfect to mount on top of my shade sail posts.
Planning the Design
100 watt solar panels are fairly large and heavy (around 30″x40″ and 20 lbs). So I needed to come with with a sturdy design to mount the panels on the posts.
Here is the design I came up with:
Adjustable Mount for the Solar Panel
The solar panel would be attached to an adjustable mount.
It’s adjustable because it can change the angle of the solar panel to maximize electrical generation.
Depending on your geographical location, adjusting the tilt of the solar panel in the summer and winter can help ensure you get the most out of the sun’s power.
The adjustable mount would then be attached to a fixed post mount.
On the opposite side of the post would be a small weatherproof enclosure to store the battery and charge controller.
The globe lamp fixture was affixed to the top of the post.
With the design flushed out, it was time to start constructing the parts.
The weatherproof enclosure for the battery and charge controller consisted of two separate compartments. The upper compartment stored the battery, while the lower compartment housed the charge controller.
The first step of the building the enclosure was constructing the box.
Here are the cut out sides of the box:
I joined the sides of the box together with construction adhesive and finishing nails.
A bar clamp came in handy to hold the pieces in place while I used my finishing nail gun:
Here I inserted the battery and charge controller to get a rough idea of how things would look:
The charge controller would later get a more elaborate design to allow it to be easily removable for installing various wires.
Deep cycle batteries can get a little warm when charging, so I drilled some ventilation holes in the side of the enclosure. I made sure to drill the holes at a 45 degree angle to prevent rain water from dripping in.
There was also a hole at the bottom of the battery section to run a wire to the controller.
Here I covered the interior of the holes with insect screen to prevent my enclosure from housing unwanted visitors:
Next I stained the enclosure with weatherproofing stain (same one I used to protect the shade sail post). I also caulked the inside corners for extra protection against water seeping in from the outside.
Here I’m getting ready to attach a 1/4″ plywood roof:
I had some roofing material left over from a prior shed project, so I was all to happy to be able to use them again.
To waterproof the roof, I first laid down a layer of roofing felt, aka tar paper (I used some staples to hold the paper to the wood):
Next I cut two strips of shingles and nailed them down to the enclosure:
The upper shingle strip covered the nail heads for the strip below.
However, with no other shingles to overlap the upper shingle, there were exposed nail heads on that shingle.
So I used some roofing cement to cover those nail heads and blend them into the shingle.
With the enclosure roof done, I used my table saw to cut out covers for the battery and charge controller compartment.
The battery cover was just a piece of 1/4″ plywood. The charge controller cover was made from a strip of 1/8″ plexiglass.
I wanted the charge controller to remain visible so I could monitor the system status without having to remove anything.
The controller came with a handy digital display with various bits of information (like if the solar panels were charging, or what the remaining charge on the battery was).
Here is the mostly completed enclosure (I still had to stain the battery compartment cover):
Solar panel charge controller module
To make it easier to attach all the wiring to the charge controller, I came up with a module design that allowed the controller to be easily removed.
The charge controller was attached to a rectangular piece of wood (with some handy 1/2″ screws), which was secured to the enclosure via two short deck screws.
Instead of attaching the wires from the battery, solar panel and lights directly into the controller, I opted to use a terminal block as a middle man. It was attached on the opposite side of the controller module.
Here’s the front of the controller module showing the charge controller wired up and ready for action (notice the addition of a toggle switch to manually turn off the lights):
Here’s the back of the module showing the terminal block, awaiting connections from the peripherals (lights, battery and solar panel):
Constructing the Solar Panel Mount
With the enclosure complete, I moved onto the solar panel mount.
It was a relatively simple design in the shape of an “I.”
I used 2×6 boards for maximum strength.
Here are the mount parts placed roughly in place on top the solar panel:
I joined all the pieces with long deck screws. I also reinforced some of the joints with L brackets and structural screws:
Here is what the solar panel looks like when attached to the mount:
Building the Post Mount
Next I built the post mount. It was in the shape of an “H”, and also made of 2×6 boards:
At his stage, the post mount was a pretty simple design. I had later decided to add in 45 degree supports made from 2x4s to further strengthen the entire mount.
How do the solar panel and post mount work together?
The solar panel mount would sit in between the segments of the post mount. They would be connected with 4 heavy duty bolts.
Two of the bolts would allow the solar panel mount to freely rotate to a desired angle. The remaining bolts would lock in the chosen angle.
During construction, I had pre-drilled bolt holes in the mounts to allow for a 45 degree tilt of the solar panel. When the mounts were securely attached to the shade sail post, I planned on drilling another pair of holes to accommodate a 30 degree tilt.
Here are the two mounts connected to each other (only one pair of bolts were inserted, so the solar panel mount could rotate freely in the post mount):
Weatherproofing All the Wood
To protect the wood from the elements, I applied at least 2 coats of weatherproofing stain to all exposed surfaces.
Here’s a picture of the post mount (with some 45 degree 2×4 supports added) showing some of the staining in action:
To secure the 2×4 diagonal supports to the 2×6 boards, I drilled some pocket holes, and reinforced the connection with 2 metal ties.
Last Minute Lamp Fixture Mounts
Here is a close-up of some mounts I made for the lamp fixtures:
These lamp fixture mounts weren’t in my original design.
The lamp fixtures were originally intended for a 3″ diameter round post, not a 6×6 square post. So I was having a lot of difficulty accessing some of the screws for the lamp fixure when attaching them to the posts.
I decided to raise the lamp fixtures about 1.5″ above the top of the posts for more clearance.
I made the mounts with some 2×4 cuts. Then I drilled a hole in the center with a hole bit, and counter-sunk some screw holes for attaching to the posts.
Solar Parts Coming Together
Everything was built at this point and finally ready to be assembled outside.
First, I installed the post mount (secured to the lamp post with 12 galvanized lag bolts):
Then the solar panel mount followed (attached to the post mount with 4 heavy duty bolts):
I was really excited to secure the solar panel to the mount next, tilted to 30 degrees. I used some structural screws to fasten the solar panel to the mount.
The battery and charge controller enclosure went on next (mounted to the lamp post with 2 galvanized lag bolts and large washers):
Then the first lamp fixture was installed on top of the post:
Next, I dug a shallow trench towards the other lamp post to run some landscaping wire to:
I buried the landscaping wire and compacted the ground with a tamper. There was now no trace of a wire running between the two posts.
Next, I wired up the second lamp fixture on the remaining shade sail post:
Finally, I hooked up the lamps to the solar panel charge controller, and was able to successfully test the lights. Here’s a close-up of the charge controller in action:
Solar Panel Lights Completed!
The solar powered lights were finally complete!
It was a really fun project to work on. I was able to build everything within 3 days and a budget of around $250. It was expensive, but using the parts I have, I can hook up other backyard items to the solar power too.
I tested the system during the night and it worked flawlessly.
When the sun went down, the lights came on and remained on all night.
By morning, the remaining battery charge was around 70%. By afternoon time, the battery was back up to full charge from the solar panels, ready for another night of work.
Here is the completed project: