These instructions will show you, with step-by-step videos, one of the fundamental skills of building DIY solar power systems: how to connect a solar panel to a battery.
By the end, you’ll be charging your 12 volt battery or higher with free solar power.
(If that doesn’t get your blood pumping…I don’t know what will .)
Very good. Let’s get to it!
Materials and Tools
Materials
Note: I have I have listed the sizes I used and linked them to the exact materials I purchased for my setup or materials that are compatible with it. Feel free to copy my settings. If not, adjust your component sizes for the amount of current that will flow through your system.
- 100 Watt 12 Volt Solar Panel
- Battery 12 Volt
- Renogy Wanderer 30A Solar Charge Controller
- 12 Gauge Wire
- 12 Gauge Wire Connectors
- Solar Adapter Wires MC4
- MC4 Solar Extension Cables (if required)
- MC4 15 Amp Inline Fuse
- Inline Fuse Holder with 20 Amp Blade Fuse
- Heat Shrink Tubing
- Gloves
- Safety Glasses
Tools
- Screwdriver</li
- Wire stripper
- Wire crimper
- Wire cutter
- Hot air gun
Step 1: Understand the Wiring Diagram
This is the diag wiring branch showing how to connect a solar panel to a battery:
It is important to understand the following:
- Do not connect a solar panel directly to a battery. Doing so can damage the battery. Instead, connect the battery and solar panel to a solar charge controller.
- It is recommended that you merge your system. Security best practices, y’all! Place a fuse between the positive battery terminal and the charge controller. Run another one between the positive cable from the solar panel and the charge controller.
Step 2 – Make the Battery Cables
I didn’t have pre-made battery cables lying around . So I decided to save some money and make my own.
Turns out it’s pretty easy. Here’s how I did it:
Cut two pieces of wire to the length you want and strip both ends. (I made one a little shorter to account for the fuse I’m going to put on it.)
Place the fuse in the fuse holder. Use our fuse size calculator to find the correct fuse size.
Connect one of the wires from the fuse holder to your shorter battery cable with the wire connector of your choice. (I used a 12-10 gauge butt-splice connector.)
Wrap the connector with heat shrink tubing and a heat gun.
Slide a piece of heat shrink tubing into each battery cable (before you crimp the terminal connectors… don’t forget till later, like I did 😅).
Next, crimp the battery terminal connectors onto the battery cables. battery and wrap the connections. Look at your battery terminals to find out what size connectors to use. Mine uses 1/4″ ring terminals.
Complete battery cables!
Now they are ready to connect. ⚡
Step 3: Connect the battery to the charge controller
Note: At this point I put on gloves and safety glasses because places like Advanced Auto The parts are recommended to be used when working with batteries.
Follow the instructions in your charge controller manual to connect it to the battery. I’ll show you how to connect the charge controller I used, the Renogy Wanderer:
Connect the negative battery cable, the one without a fuse, to the “-” battery terminal on the charge controller.
Connect the positive battery cable, the one with the fuse, to the “+” battery terminal. (Renogy recommends connecting the battery cables to the charge controller before connecting them to the battery.)
Connect the battery cables to the battery terminals: negative first, then positive. Before connecting the positive cable, I like to touch the positive battery terminal because sometimes there is a small spark.
The charge controller should turn on or light up to indicate that the battery is properly connected. For example, mine has a light that turns on.
Battery is now connected!
At this point, your manual may tell you how to program the charge controller for your battery type, voltage, etc.
Mine has a button that I can press to indicate the type of battery. The default is Sealed Lead Acid, which happens to be the type I’m using. So I kept it in the configuration it was in.
Step 4: Connect the solar panel to the charge controller
Next, connect the solar panel!
Most solar panel cables come with MC4 connectors pre-installed. To connect a solar panel to a charge controller, you need MC4 solar adapter cables.
(These are basically a length of solar PV cable that has an MC4 connector on one end and is bare on the other. For my setup, I made mine by assembling a male and female MC4 connector. I also purchased the MC4 Solar Extension The extension cables are optional depending on the distance between the solar panel and the charge controller).
For the positive cable of the panel, connect the MC4 in-line fuse, the positive extension cable (if used) and then the MC4 adapter cable.
For the negative panel cable, connect the negative extension cable (if used) and then the adapter cable MC4. Do not allow exposed wires to touch!
Follow the instructions in your charge controller manual to connect it to the solar panel. I’ll show you how I connected mine:
First connect the negative solar cable to the charge controller, then connect the positive. Your charge controller should light up or light up to indicate the panel is properly connected.
Now everything is connected!
Just one more step…
Step 5: Position the solar panel in the sun
Place your solar panel in direct sunlight at the best tilt angle for your location (this is easy to do with my DIY solar panel mount from $11).
Once you do, your charge controller should indicate that the battery is charging. Mine has a light that blinks when the battery is charging normally.
Just like that, IT WILL BE DONE. 🥳
Now you know how to charge a battery with a solar panel!
Sit back and let the panel collect all that free solar energy. The charge controller will stop charging the battery once it is full.
How long does it take to charge a battery with a solar panel?
Use our charge time calculator solar battery to find out. The answer depends on many factors.
As an example, here are the specifications for the setup I used:
- 12V 33Ah Lead Acid Battery
- 50% battery depth of discharge
- 100 watt solar panel
- PWM charge controller
Based on our calculator , with this setting the battery will take about 4.5 peak sun hours to fully charge.
But change any part of the setting eg. swap in a 50-watt solar panel, lithium battery, or MPPT charge controller, and the charge time will be different.
So yeah, I definitely recommend the calculator for that question.
Give It A Try:
3 DIY Solar Power Projects You Can Build Now
What you effectively just built was your first solar panel setup. That’s a big deal!
Now that you’ve passed that milestone, here are a few more projects I think you’d be interested in building:
1. Solar Car Battery Charger
By connecting a solar panel to a 12V battery, you have actually created a 12V solar battery charger. Car batteries are 12V, so you could easily use the system you just created, or the nearly identical one described in this tutorial, to solar charge your car battery.
2. DIY 12 Volt Solar Powered LED Lights
These solar powered LED lights essentially use the same system you just built. All you need to do now is connect some LED strip lights to your battery and you’re good to go.
3. Solar Charger for Electric Bike
You can build a modified version of the solar charging system you just made to charge an electric bike with solar energy. Or just connect an inverter to your 12 volt battery and plug in the e-bike charger as normal.
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