Solar panel to plug in christmas lights

A string of solar Christmas lights uses a small solar panel for power; there are no extension cords that must be plugged into outlets.

The panel -- about the size of a hockey puck -- powers rechargeable batteries that illuminate a 25- to 100-bulb string of LED lights.

Panels come with small stakes so you can put them in the ground, where they can take advantage of the sun. 

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#2 They Cost About the Same as LED Lights

Pricing for solar-powered and plug-in LED holiday lights runs neck and neck. A string of 100 miniature lights costs about $10 and up for both solar and LED. Yet solar costs nothing to operate.

#3 They're Durable

They don't have any filaments that burn out easily, and they're made of plastic, which doesn't break as easil as glass.

#4 But They May Not Be as Bright as You'd Like

A fully-charged string of lights should glow for a few hours after the sun goes down. But if you don't get much sun, and with the shorter days, you could see only an hour or so. 

Just so you know, this page contains affiliate links. If you make a purchase after clicking on one, at no extra cost to you I may earn a small commission.

I recently made my own DIY solar string lights.

Check them out:

Turns out it’s easy to convert string lights to solar lights. And they’re versatile, too.

You can use them as solar powered outdoor string lights. You can hang them in your bedroom as solar powered fairy lights. You can even hang them up over the holidays as solar powered Christmas lights.

Here’s how to make them:

Materials & Tools

Materials

• 12V solar panel – I used the Newpowa 5W 12V solar panel
• 12V battery – I used a 12V 33Ah battery
• Renogy Wanderer 10A solar charge controller
• USB LED string lights
• NOCO GC018

Tools

• Wire cutter
• Wire stripper
• Screwdriver

Step 1: Connect the Battery to the Solar Charge Controller

To connect battery and solar charge controller, you’ll need appropriately sized wire, wire connectors, and fuses.

To make this part easy, I used a 12V plug adapter called the NOCO GC018 rather than make my own battery cables. The GC018 comes with ring terminals that are compatible with my battery, plus an inline fuse.

First, I cut the 12V plug socket off the NOCO GC018.

Next, I stripped the cut wire ends so I could connect them to the charge controller.

I located the battery terminals on the charge controller, which are indicated with a battery icon.

Then I inserted the positive and negative stripped wire ends into their respective battery terminals on the charge controller. I used a precision screwdriver to tighten them in.

Next, I screwed on the GC018’s ring terminals to their respective positive and negative battery terminals on the 12V battery.

When all wires were connected, my charge controller turned on to indicate that it was properly connected to the battery.

Note: My charge controller’s manual recommended I first connect charge controller and battery. Consult your controller’s manual for the manufacturer’s recommended connection order.

Step 2: Connect the Solar Panel to the Solar Charge Controller

Next, I needed to insert the solar panel wires into their screw terminals on the solar charge controller.

My solar panel’s wires came with stripped wire ends, making this step super easy for me.

If your solar panel comes with MC4 connectors, you’ll have to buy or make MC4 adapter cables to connect them to your charge controller. You should also consider adding an MC4 inline fuse.

First, I located the solar panel terminals on my charge controller.

Then I inserted the positive and negative solar panel wires into their respective terminals. Once again, I used a precision screwdriver to tighten them in.

My solar panel is now connected to the battery via the charge controller. I just need to connect the lights and I’ll have built my own DIY solar powered string lights.

Step 3: Connect the LED String Lights to the Solar Charge Controller

I located the USB port on my solar charge controller.

Then I plugged the lights into the port.

Yep — it’s that easy.

Now my DIY solar string lights are complete!

Here’s the complete setup at this point:

Time to test them out to make sure everything is working.

Step 4: Test Your Solar String Lights

I first tested the lights by turning them on:

Lights — check. ✅

Tip: If your lights aren’t turning on, cover your solar panel with a blanket and try again.

Then I tested that my solar panel, battery, and charge controller were all properly connected by putting the solar panel outside in the sun. (Being careful that no wires disconnected during transport.)

With the solar panel getting direct sunlight, I looked at the charge controller’s display and waited for the PV current display to appear.

When it did, it showed that the solar panel was charging the battery at a rate of 0.1 amps.

Solar charging — check. ✅

Note: Connecting the lights to the USB port on the solar charge controller is convenient. However, it is also limiting because it only works when the solar panel isn’t charging the battery. Put another way, lights you connect to the USB port will only turn on at night, or when the solar panel is covered.

Step 5: Hang Your Lights

Like I said in the intro, these DIY solar string lights are versatile.

You can hang them on your porch or patio as solar powered outdoor string lights.

Tip: If you hang our string lights outdoors, make sure to keep the battery and charge controller dry by mounting them inside. You may have to extend the solar panel wires to do this.

Or you can hang the string lights in your room — what some people call LED fairy lights.

Tip: For this setup, you may have to mount the solar panel in your bedroom window. I’m fortunate that my window gets direct sunlight — if yours doesn’t, this option may not work. Solar panels work behind windows, but with a reduced output. Take that into account when deciding which size solar panel to get.

Come December, you can even hang them in your yard as solar powered Christmas lights. 🎅

DIY Solar LED String Lights Circuit Diagram

Here’s the solar lighting circuit diagram for this project:

And here’s what it looks like when built:

Notes about this solar light circuit:

• Lights connected to the charge controller’s USB port will only work when the solar panel isn’t charging the battery. In other words, these lights won’t work during the day. (If you want solar powered LED lights that can work during the day, check out this tutorial.)
• Safety best practices are to place an appropriately sized fuse between the charge controller and both battery and solar panel.
• I used a PWM solar charge controller because they’re a lot cheaper. Make sure to get one with a USB port!

How I Sized My Solar Lighting Circuit

My goal was to make solar LED string lights that could last for an average of 2 hours each night.

Here’s how I sized my system to reach that goal.

LED String Lights

According to the wall plug on my LED string lights, the max power they consume is 1 amp at 5V DC. That means they consume a maximum of 5 watts (1A * 5V = 5W).

I plan to use them on average for 2 hours a day, so I do the following calculation to estimate their energy usage in watt hours:

5W * 2 hrs = 10Wh

I estimate the lights will consume 10Wh of power per day.

Tip: I recommend getting LED lights because of how energy efficient they are. If you get lights that are less efficient (e.g. incandescent bulbs), you’ll have to buy a bigger solar panel and battery.

12V Battery

I used a 12V battery that I already had. But if I had to buy a new one, I’d size it like so:

My lights use 10Wh every night. And, to account for rainy days, let’s say I want to buy a big enough battery that it can power the lights for 3 days without sun.

10Wh * 3 days = 30Wh

So I need a battery that can store up to 30Wh of usable capacity.

I’ve decided I’ll go with a 12V lead acid battery because they’re cheap. However, lead acid batteries only have 50% usable capacity.

This means I need a 60Wh lead acid battery in order to get 30Wh of usable capacity.

60Wh / 12V = 5Ah

If I were buying a new battery, I’d get at least a 5Ah 12V lead acid battery to meet my energy needs. I’d probably size up to 7Ah or 8Ah to give myself a little wiggle room.

Solar Panel

I want the solar panel to recharge my battery every day.

My lights use 10Wh of power a day. My solar panel needs to produce at least that much power every day on average. To account for cloudy days, let’s go ahead and get a solar panel that can produce double that — up to 20Wh per day.

For this calculation, I’ll use a rule of thumb I learned from my solar biking adventures: On average, a solar panel produces about 4Wh per watt. (This rule of thumb is for solar panels mounted to an ebike, so depending on your location and how much sunlight your panel receives, it could produce more or less.)

20Wh / 4Wh per watt = 5W

So to produce 20Wh per day on average, I need a 5W solar panel. And it needs to be a 12V solar panel in order to work with my charge controller and charge my 12V battery.

Note: If you plan on putting your solar panel behind a window, size your solar panel bigger to account for the reduced output.

Charge Controller

I needed a charge controller that was compatible with 12V lead acid batteries and capable of handling the max current output from my solar panel.

I picked up a cheap PWM charge controller that works with 12V lead acid batteries and has a 10A current rating.

2 More DIY Solar Lighting Projects You Can Build Now

Over the years I’ve made plenty of DIY solar lighting projects.

Now that you know how to convert string lights to solar lights, here are some other projects I think you’ll be able to build no problem.

1. DIY Solar LED Strip Lights

Here’s a similar solar lighting circuit to the one you just made. But rather than string lights, this one uses 12V LED strip lights that are brighter and better suited for indoor use.

In this project, I connect the LED strip lights directly to the battery instead of to the USB port on the solar charge controller. This means the lights can be turned on at any time of day.

2. Solar Shed Lights

This solar shed lighting system is designed to light up a shed for nighttime use. I also include ways you can add on to it to power AC devices such as power tools. I go a lot more in depth on the installation part of the process — such as how I mounted the solar panel and hung the lights.

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Alex Beale

Hi, I'm Alex. I’m a DIY solar power enthusiast on a journey to learn how to solar power anything. Footprint Hero is where I’m sharing what I learn – as well as the (many) mistakes I’m making along the way.

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