Each year we speak to and receive emails from a number of people who are interested in solar power Christmas lights. We’ve looked at several options for solar powered Christmas lights and found that most of the stuff that is on the market today simply isn’t very good. Most of the units we have looked at have solar panels that aren’t large enough or of high enough quality to collect enough light to charge even a small battery. Additionally, the batteries on the sets we have tested all seem to be very low quality and don’t hold much of a charge. And worst of all, the lights weren’t even very bright. The average light output of the solar powered Christmas lights we tested had light output that was comparable to a dim power indicator light on a DVR or something. Since we couldn’t find any good solar power LED Christmas light sets we decided to make our own.
List of Materials
Working with a modest budget of around $200.00 we purchased everything that we needed for our solar powered Christmas light set up. (This may seem like a lot to those who have shopped around for solar Christmas light sets and found them for under $50 for the complete unit but anyone who has tried them will tell you they aren’t worth $5.) We were also able to purchase everything that we needed to complete the project at local stores like Menard’s. Most of the items in our materials list are also widely available online. With a few minutes on the computer or a quick trip to your local store you can have everything you need to create your own solar powered Christmas lights. Here is what you’ll need (*we are listing the exact materials we purchased the set up we constructed and which we feature in our video. We will add some comments throughout this article about what we think you might be able to do to improve the efficiency of the set up.):
- SunForce 15W Solar 12v Battery Charger Kit
- 2 Spade Terminals
- 2 Push on female spade terminals
- Victor 12v Power Outlet
- Peak 100W Power Inverter
- Woods Heavy Duty Timer
- Huskee 165 CCA Lead Acid Battery
- A plastic battery cover (We got ours at Tractor Supply but you can find them most anywhere.)
- 8 sets of 50 light LED Christmas lights
Those are the items we picked up to build our solar powered Christmas lights set up. I think this could be improved and I would suggest that you consider a larger battery than what we used. The ideal battery would probably be a deep cycle marine type battery. This battery unit will be a bit more expensive but if you are serious about having a viable solar powered Christmas light set up this is definitely the way to go. I also think the power inverter we used would have been ideally a 50W inverter. The inverter also had a built in fan designed to cool the unit when it was handling larger amounts of power which isn’t necessary for our application. I suspect that the fan used as much power as or more than the LED Christmas lights. I spent some time looking around online and couldn’t find any lower wattage 12v inverters that didn’t have a built in cooling fan so this is something you might have to compensate for with a larger battery.
Building the Solar Power Battery Charger Unit
Putting the solar panel and battery charger unit together with the power inverter was relatively simple. The SunForce solar panel unit came equip with basically all the connections we need to get this going and we only needed to add a few things that can easily be done even if you are not an electrician or even considered to be “handy.”
- The first step is to install the terminal connectors to the battery. The connectors are fastened to the two positive and negative terminals on the 12v battery using a simple nut and bolt assembly. Fasten the connectors tightly to each terminal on the battery.
- Next, bring the positive and negative wires from the 12v power outlet and the connection wire included with the solar panel unit together so you have two parallel wire lines. Tape the two positive wires and the two negative wires together using some standard electrical tape. Twist the wire ends of the positive and negative wires from the 12v outlet and the solar panel wire together and insert them into the connection end of the 2 female space connectors. (It’s probably best to solder the wires to the female spade terminals.)
- Next, insert the male end of the 12v power inverter into the female end of the 12v power outlet. This is as simple as plugging something into the cigarette lighter in your car.
- Once you have connected the power inverter, plug the outdoor timer into the outlet on the power inverter. Although, the timer is not required we recommend using one so that you can set the lights to run only during certain times and conserve battery power.
- The next step is to connect the solar panel wire to the solar panel unit. The wire which was included with the unit we used had a simple male/female connection system so it was easy to connect.
At this point, the solar panel and battery assembly are ready to go. The battery you purchased is likely already fully charged so it will not require initial charging. You are now ready to position your solar unit for maximum efficiency.
Installing and Positioning the Solar Panel
We didn’t spend any time trying to figure out the best way to mount the solar panel but it will need to be mounted to a pole, tree, or some other object. It should be mounted in a manner so that it can be easily adjusted as necessary in order to receive maximum sun exposure. (I can imagine many sets up and I might figure something out later. If I do I’ll post something about it to share what I learned.) Once you have figured out a suitable method for mounting the solar panel it you need to look at some data for your geographic area to determine the optimal tilt and angle orientation for the solar panel. There are several websites out there that provide charts and explain how to make this calculation for your geographic area. This site has a pretty cool solar angle calculator. Be sure to take the time to look at one of these sites, make the calculations for your area, and take the time to position your solar panel properly–it can make a huge difference in performance.
Once you have determined the best angle and position for your solar panel, install the unit at the appropriate angle at a location near the site of installation. You may need to use some extension cords but we would recommend that you minimize the use of extension cords to avoid losing power due to voltage drop.
Install Your LED Christmas Lights
The final step is to install your LED Christmas lights. With the small tractor battery we purchased we were able to run 8 sets of our 50 light LED wide angle Christmas lights for about 4 hours. If your display requires more than 400 lights or you want them to operate for more than 4 hours a day you should purchase a larger battery. Each of these light sets consume about 4 watts so the total draw for our set up was 32 watts. This works out to be 128 watt hours. According to this watt calculator 5 hours of direct sunlight collected on a surface of 1.65 square feet would be required to produce this much energy. This (I assume) considers a collection surface which is 100% efficient and even high end solar panels are not this efficient.
After you have installed the Christmas lights, plug the lights into the outlet on the time and set the timer to turn the lights on and off at the desired time. The solar panel will continuously charge the battery.
Depending on your location and the time of year you may find that the solar panel does not gather enough sunlight to adequately charge the battery. There are two potential solutions to this. The first is to purchase a larger or more efficient solar panel unit but these can be costly. A less expensive option would be to buy an extra battery. You could charge one battery during the day with the solar panel and then take it inside and top it off with a standard 12v battery charger. each night you could swap the fully charged battery with the one which was being charged with the solar unit during the day.
We are currently have our solar panel unit installed outside in southern Michigan. Today is a nice sunny day so we will see how long it takes to charge the battery. I will update this post with more information as we conclude our experiment.