If you’re using an off-grid solar panel you’ll need to connect it to a battery supply.
Without a battery, you won’t be able to generate reliable levels of power.
Adding to this, you’ll have nowhere to store your solar energy for use when the sun goes down.
This makes it crucial to connect a solar panel to a battery correctly.
Making a mistake in your circuit could immediately damage your equipment.
At the very least, it will stop your solar panel system from working efficiently.
For example, you must hook up your charge controller, battery, and panel in the correct order to avoid trouble.
Don’t worry.
Together, let’s go through everything you need and the step-by-step process of connecting a solar panel to a battery.
This article is written as a guide with common equipment and processes in mind. If you are not confident, I highly advise asking a professional for help.
What You’ll Need Equipment and Tools
Let’s go through what equipment you will need to complete the task. If you have purchased a solar panel kit then you should find all the essential components ready to use. In some cases, you might need to create battery cables yourself using wire strippers, crimpers, and lugs. (You can easily buy all the cables ready-made too!)
- Solar Panel
- Solar Charge Controller
- Deep Cycle Battery
- Battery Cables
- MC4 Solar Adaptor Cables
- In-line Fuse (optional)
- Screw Driver
- Wire Cutter and Crimper (if making wires yourself)
- Gloves
- Safety Glasses
1. Wiring Diagram
Below is a wiring diagram to help you visualize how everything connects together before you start.
It consists of 3 main components. Firstly, the solar charge controller connects to the battery using battery cables (Always do this first). Secondly, the solar panel connects to the solar charge controller with MC4 adaptor cables.
2. Consider Adding an In-line Fuse
One decision you need to make before starting is whether you want to add an in-fuse between the battery and the charge controller. Many people fuse to the battery cables as it protects the circuit between the two components.
It is a useful safety addition in permanent installations. For example, should the wires become exposed and touched then your fuse will protect you from a short circuit.
You should use a fuse that is 5A or 10A bigger than the output capacity of your solar charge controller. For instance, a 15A fuse with a 10A charge controller.
3. Connect the Solar Charge Controller to the Battery
The first thing you need to connect is the solar charge controller to the battery.
It is very important that you always do this step before connecting the solar panel. If you try to wire the solar panel to the charge controller before the battery you can damage your equipment. This is because the solar panel will start sending electricity to the charge controller when it has no ability to output the current. You can easily destroy your charge controller by doing this!
Wire the battery cables to the charge controller
At this point you should put your gloves and safety glasses on. Deep cycle batteries can give off sparks and even acid when you are working on them. To be safe, protect your skin and eye from any faults as you go.
To connect the charge controller to the battery you will need a set of battery cables.
The end that connects to the charge controller should have stripped ends to allow you to insert into the controllers positive and negative output terminals.
You should be able to see a battery symbol along with + – marks. Insert the red wire (positive) into the + terminal and the black wire (negative) into the – terminal. Ensure you tighten the screw for a snug connection.
Wire the battery cables to the battery
Next you can connect the battery cables to the positive and negative terminals on the deep cycle battery.
It is best to use O-ring lugs for a secure permanent connection. Although, you can use alligator clips if you’re in a hurry.
Start by connecting the red positive wire to the positive terminal on the battery. Next connect the black negative wire to the battery.
4. Connect the Solar Panel to the Charge Controller
With your charge controller and battery safely connected you can now connect your solar panel.
The solar panel should be wired to the solar charge controller. To do this you will need MC4 adaptor cables.
MC4 connectors are used to connect solar panels together, and should be pre-installed on the wires on your solar panel. They will look like this:
Unfortunately, you won’t be able to connect an MC4 directly to your charge controller. So you will need adaptor cables. These have an MC4 connection on one end and stripped wire at the other end.
Simply, connect the MC4 ends of the cables into the solar panel. (Positive to positive and negative to negative).
Next, connect the stripped wire ends into the solar charge controller just like you did with the battery cables.
Now your solar panel system should be completely connected together. The current can flow from the solar panel to the charge controller. Then from the charge controller into the battery.
How Quickly Will a Solar Panel Charge a Battery?
There are various factors that go into how long it takes a solar panel to charge a battery.
You must take into account the amount of sunlight, solar panel power, and battery size.
Obviously the bigger the battery the longer it will take to charge. Plus, the larger the solar panel and brighter the sunshine, the more energy you will produce.
To give you a better idea, we will look at how long it takes a 100 watt solar panel to charge a 12v battery.
You can expect a 100 watt solar panel to produce around 6 amps of energy per hour on a sunny day. Or about 30 amps per day.
Using this knowledge, you can estimate how long it will take to charge a battery by using the formula:
Battery capacity in Ah ÷ Solar panel amps = Charge time.
For example, 50Ah battery ÷ 6A = 8.3 hours.
So a 50Ah battery will take 8 hours to charge from a 100 watt solar panel.
Can I Connect a Solar Panel Directly to a Battery?
You should never connect a solar panel directly to a battery. This is because you won’t have any way to regulate the charging. The solar panel will continue to send energy to the battery even when it is fully charged. Overcharging a deep-cycle battery is dangerous and will lead to damage and even explosions.
You should always connect a charge controller to your battery. Then connect the solar panel to the charge controller. This enables you to safely charge your battery without risk of overcharging and reverse charging.
Where Do You Plug a Solar Panel into a Battery?
To plug a solar panel into a battery you will need a solar charge controller. This charge controller is what connects the panel and battery together. It allows you to safely plug a solar panel into a battery while monitoring the flow of energy from the panel to the battery. Your charge controller directly connects to the battery using the positive and negative battery terminals. Then your solar panel plugs into the input terminal on the controller.
What Size Solar Panel Do I Need to Charge a 12 Volt Battery?
You can use any size solar panel to charge a 12V battery. Obviously, the bigger the solar panel the quicker it will charge your battery. The most popular size is a 100 watt solar panel. This gives you a nice balance of size and power output to keep batteries charged. Adding to this, you can always connect up multiple panels to your system to increase power output.
How Do You Charge Multiple Batteries with One Solar Panel?
To charge multiple batteries with one solar panel you must connect the batteries together. You can directly hook up batteries using battery cables and battery terminals. Do your research before attempting this as you need to connect the batteries correctly. This is because you can wire them in either parallel or series. Wiring multiple batteries in series will increase the voltage. Wiring them in parallel will increase the storage capacity.
Read my guide on How to Connect Multiple Batteries to a Solar Panel.
Final Words on Connecting a Solar Panel to a Battery
I hope this guide gives you a much clearer idea of how to connect a solar panel to a battery.
Once you understand the different components of your system it is not too complicated.
With the correct equipment, it takes two simple steps.
Always start by connecting the charge controller to the battery. Then all you need to do is wire the solar panel to the charge controller.
In addition, many people add an in-line fuse to the positive wire between the battery and the charge controller for extra safety.
That’s all there is to it!
Thanks for reading.
