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Last Updated on February 7, 2024
Solar panels are awesome ways to harness the power of renewable energy. Using them allows you to not only save money but to also make a positive difference for the planet. Solar panels can be used for a variety of different things, from providing your house with electricity to powering your car.
Many people also use solar panels to charge their rechargeable batteries, whether these are car batteries or some other type. Typically this process involves using a charge controller, but many people wonder if they can skip that step and directly connect their solar panels to their battery. In this article we answer that question and more to help you better understand the awesome power of solar panels.
Can I charge a battery directly from a solar panel?
A solar panel may be directly attached to a 12V automobile battery, but its output must be monitored if it exceeds 5W. Solar panels with a power rating more than 5 watts must be linked to a battery through a solar charge controller to avoid overcharging.
What Do Charge Controllers Do?
Charge controllers are voltage or current regulators that help keep batteries from overcharging. This is a crucial component to have when charging batteries with solar panels because if your solar panel is rated higher than five watts, it can overcharge your battery and damage it.
Car batteries, for example, are usually 12 volt batteries. Most solar panels, on the other hand, are capable of producing up to 20 volts of power. Without a charge controller the solar panel would overcharge a 12 volt battery.
With a charge controller, however, you don’t have to worry about this problem. Charge controllers are, in essence, voltage gatekeepers that monitor the charge capacity of your battery and cut off the flow of power when the battery is fully charged.
How Do Solar Panels Work?
We surely all agree that solar panels are pretty awesome, but that doesn’t mean we all understand how they work! The answer is simple enough: when sunlight hits a solar panel’s cells, a chemical reaction occurs that produces direct current (or DC, for short).
The DC is what powers your home, car, or battery, and how much DC is generated depends on the capacity of your solar panels. However, neither batteries nor solar panels are capable of monitoring or managing how much power is sent into the battery, which is why charge controllers are necessary.
See Also: Best Solar Generators
How To Safely Connect Solar Panels to a Battery (with a Charge Controller)
Since we’ve established the importance of using charge controllers, let’s move onto a step-by-step guide for how to connect your solar panels to a charge controller and your battery.
1. Get Familiar With It
The first step when embarking upon any DIY journey that involves wiring, electricity, or any other kind of safety hazard is to familiarize yourself with the setup and the objective. To do this, find a wiring diagram online that shows the wiring pathways for a solar panel, charge controller, and battery.
We also recommend that, per the best safety practices, you fuse your system as well. To do so place the first fuse between the positive terminal of the battery and the charge controller. Then, place the second fuse between the positive solar panel wire and the charge controller.
2. Grab Your Battery Cables and Connect the Battery to the Charge Controller
Once you get to this step, we (and many other professionals) recommend wearing safety gloves as an extra safety measure.
You should also make sure that you have the manual for your charge controller handy during this step.
Consult the charge controller manual for instructions on connecting the charge controller to your battery. This is important because directions will vary depending on which charge controller you use, so make sure you pay close attention.
In all likelihood, it will say something along the lines of the following:
Connect your negative battery cable to the negative battery terminal on your charge controller.
Then, connect the positive battery cable to the positive battery terminal. Once you have properly connected the cables you should see a light come on on your charge controller telling you the connection was made properly.
Depending on the charge controller you have you may also need to program it for your specific battery at this point.
3. Connect the Charge Controller to the Solar Panel
You may notice that your solar panel has special, pre-attached cables on it. These are MC4 connector cables, and most solar panels have them. You will need MC4 solar adapter cables to connect your panel to a charge controller.
Starting with the solar panel’s positive cable, you’ll want to connect the MC4 inline fuse with a positive extension cable and then to the MC4 adaptor cable.
With the negative cable you’ll want to connect the negative extension cable to the MC4 adaptor cable.
- Do not let the exposed wires touch each other*
Follow your solar panel’s instruction manual to connect to the charge controller. It should say something like this.
Connect the negative solar cable to the charge controller first and then connect the positive one. Again, your charge controller should light up to indicate the connection was properly made.
4. Lastly, Place the Solar Panel in the Sun
Last step! Place the solar panel in the sunlight and you’re good to go! The charge controller should somehow indicate that the battery is now charging at this stage.
How Long Does It Take a 12-V Battery To Charge With Solar Panels?
A lot of factors decide how long this process takes, but we have found that our setup usually takes around 7 hours of constant sunlight to charge our batteries to 50% capacity.
Solar power is pretty cool and is a great way to charge your drained car batteries. In order to do so safely and without damage to your battery, however, you should always use a charge controller to help controller the amount of power transferred from the solar panels to your battery.