Can a Solar Panel Charge a Car or 12V Batteries?

Yes, a solar panel can charge a car or 12V batteries.

You can charge your 12V batteries and your car’s battery (which is also 12V) using a solar panel. You just need to make sure that the solar panel is also rated at 12V. Anything less than 12V will not work.

In this article, we will discuss 12V batteries and how to charge them using a solar panel. Moreover, we will have a look at the solar-battery charging time and discuss the best/recommended solar size for charging 12V batteries.

Let’s start by looking at 12V batteries and how to charge them using a solar panel.

How to Charge 12V Batteries Using a Solar Panel?

Charging a 12V Battery Using a Solar Panel
Charging a 12V Battery Using a Solar Panel

Solar panels are made of solar cells. Solar panels generate electricity by harnessing the energy of the sunlight. The electrical energy produced may be utilized immediately or stored in batteries for future use. The 12V batteries are widely used in solar energy storage applications.

In order to charge a car battery or 12V batteries, you will need to design a small solar PV system. In order to design the PV system, you will need the following material and tools:



Step-by-step PV System Design to Charge a 12V Battery

100W Solar 12V 50Ah Battery Charger Wiring Diagram
100W Solar 12V 50Ah Battery Charger Wiring Diagram

If you’ve got the required materials and tools, it’s time to design the system step by step.

#1 Step: Connect the 12V Battery to the Charge Controller

The first step is to connect your 12V battery to the charge controller. You can connect one end of the wires (which has rings) to the terminals of the battery. Make sure to properly connect the positive and negative wires to their respective battery terminals.

The other end of the wires should be cut off and stripped. Then you can connect the stripped ends of the wire to the charge controller using a screwdriver. Charge controllers have a battery mark as well as plus and minus signs on them, so make sure to connect it properly.

Your charge controller will be switched on if you’ve completed the procedure correctly. If you’re not sure, please consult your charge controller for further instructions.

Note: The wire we have suggested above in the materials has built-in fuses so no need to connect them manually.

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

Now, it’s time to connect your 12-volt solar panel to the charge controller. You can strip the ends of your solar panel wires and then connect them to the proper terminals of the charge controller. Once again, the terminals on the charge controller will have a solar panel mark on them along with the plus and minus signs.

That’s it!

Now the system design is complete and functional.

Note: It’s important to have a solar panel with at least 12 voltage levels in order to charge the 12-volt battery. The solar panel voltage must match the battery voltage.

But, wait, how do you know what is the right size of the solar panel to charge your 12V battery? And how long does it take to charge your 12V battery?

Follow along to find out.

How Long Does it Take to Charge a 12V Battery with a Solar Panel?

The time to fully charge your 12V battery depends on your solar panel size
The time to fully charge your 12V battery depends on your solar panel size

In order to answer this question and design your system correctly; you need to know your battery capacity. Typical small cars have 40 amp-hours (Ah) battery on average. Large cars and SUVs have 50Ah battery and larger cars, RVs and boats have 75+Ah of battery.

In our case, we’ve taken the 50Ah deep cycle battery into account. It takes approx. 10.5 hours of direct sunlight to charge a typical 12V 50Ah battery using a 100W solar panel.

Here is a table that shows quick charge time estimates for 5 most common solar panel sizes:

Solar Panel SizeBattery SizeFull Charging Time
50 Watt50Ah 12V17.5 hours
80 Watt50Ah 12V12 hours
100 Watt50Ah 12V10.5 hours
150 Watt50Ah 12V7.5 hours
200 Watt50Ah 12V5.9 hours

Needless to say, that these are just charging-time estimates for a 50Ah battery and these numbers will vary for other sizes of battery and solar panel combination.

What Size Solar Panel do you Need to Charge a 12V Battery?

You can charge your 12V battery with many different sizes of solar panels. Even, solar panels as small as 5W can charge your 12V battery but with a longer charging time.

It all comes down to one question: how quickly do you want to charge your battery?

So, based on the estimates above we can conclude:

50W and 100W solar panels are good choices and can be used as a trickle charger if charging time is not of concern for you. Because they can charge a 50Ah 12V battery slowly by trickle charging. Moreover, 50W and 100W solar panels are also cheaper to buy. These setups can also be used as portable solar chargers.

Also Read: Can a Solar Panel Charge a Power Bank? Choose the right charger.

100W, 150W, and 200W solar panels are the best choice if charging time is important for you. These solar panels can charge your 50Ah 12V battery faster. For instance, a 150W solar panel can charge your 12V 50Ah battery in 7.5 hours and 200W can charge it even faster in almost 5.9 hours.

Frequently Asked Questions

Will a solar panel charge a dead car battery?

Yes, a solar panel can charge a dead car battery. But you will need to have at least a 50W 12V solar panel and a charge controller. Depending on the dead battery capacity and sizing of the solar panel, it may re-charge the dead battery in 1-2 days.

What is a charge controller?

A charge controller is a device that prevents solar panels from overcharging your batteries or battery bank. It prevents both undercharging and overcharging of the battery. Charge controllers are categorized into two types: PWM and MPPT.

What is an MPPT Solar Charge Controller?

MPPT or Maximum Power Point Tracking is a technology that allows extracting maximum possible power from your solar panels with any given conditions. An MPPT charge controller is more expensive than a PWM solar charge controller.

Can you Overcharge a Battery with Solar Power?

Yes, if you’re not using a charge controller. Overcharging can quickly damage your 12V batteries if not at least degrade them over time. For example, it may even explode due to the venting of hydrogen gas which accumulates inside a battery because of overcharging.

What is a Solar Kit?

A solar kit is a set of components that come together to help you go off-grid with your home, cabin, or RV. It typically includes a solar panel(s), charge controller, battery, and all necessary connecting cables. A solar kit can help you make a good solar car battery charger (DC Charger).

Is a lithium battery more efficient than a lead-acid battery?

Yes, a lithium battery is more efficient than a lead-acid battery. On average, lithium batteries have an 80% depth of discharge (DoD), while lead-acid batteries have a 50% depth of discharge. However, lithium batteries are more expensive than lead-acid batteries.

Aimal Khan is the founder & CEO of Engineering Passion. He is an engineer and has obtained his bachelor's degree in energy engineering from Kandahar University.