What Size Solar Panel is Needed to Charge a 12V Battery? – Everything You Need to Know About Charging a 12V Battery with Solar Panels

Updated July 6, 2023

What Size Solar Panel is Needed to Charge a 12V Battery? – Everything You Need to Know About Charging a 12V Battery with Solar Panels

If you are planning to run a fully off-grid solar power system, or you want to use solar energy to meet some or all of your power needs while you are RVing and camping, understanding what type of solar panels you will need to charge your batteries is very useful information.

If you would like to know more about charging a standard 12V battery with clean and environmentally-friendly solar electricity, you have come to the right place. We will tell you what size solar panels you will need to charge your battery, how long it will take to charge a battery with solar power, and what sort of solar equipment you can use to make sure everything runs efficiently.

What are Deep Cycle Batteries?

Before we dig into how long it takes to charge a 12V battery and explain what size solar panels you will need, it is worth explaining what deep cycle batteries are and how they function.

While a deep cycle solar battery might look like the standard automotive batteries you would see in a car or RV, they are actually quite different. What makes them stand out is the fact that deep cycle batteries are specifically designed to handle the repeated charging and discharging that occurs at rapid rates when you are using solar power.

Where car batteries are designed to provide a quick burst of power to start the engine of a vehicle, deep cycle batteries are meant to be used as a power bank that can be used to supply power to any number of connected electronic devices and appliances, including lights, televisions, smartphones, laptops, refrigerators, and just about anything else you can think of.

This is why it is so important that you actually choose a high-quality deep cycle solar battery if you are planning on storing solar electricity to satisfy your power needs. While it is possible to charge an automotive battery using solar electricity, it is better to use a deep cycle battery for running your electronics.

Outside of solar storage applications, you often find deep cycle batteries inside of small, fully electric vehicles, like golf carts and electric go karts.

Where Can You Find Deep Cycle Solar Batteries?

If you planning to store solar electricity, so you can use it at your convenience, we encourage you to take a look at our Complete Collection of Deep Cycle Solar Batteries. We carry a wide range of solar batteries from some of the most reputable brands in the solar industry. In addition to the standard 12V deep cycle batteries, we also carry a variety of 24V and 48V options.

If you are on a budget, but you would still like to purchase a reliable 12V deep cycle solar battery, we highly recommend you take the BattleBorn 100Ah 12V LiFeP04 Deep Cycle Lithium Solar Battery into consideration.

Unlike traditional lead acid batteries, the BattleBorn can be 100% discharged. It also charges up to five times faster and holds a charge ten times longer than traditional batteries.

This rugged and reliable lithium-ion solar battery can work for just about any storage application. Whether you are looking to store solar electricity for your RV, boat, home, or fully off-grid system, this highly efficient deep cycle battery is the perfect choice.

What Size of Solar Panels Would You Need to Charge a 12V Battery? 

Now that you understand what type of battery you should be using with a solar power system, we can look into what sort of solar panels you will need and how long those panels would take to charge your battery. 

The truth is, as long as you are using 12V solar panels, you can use any style of solar panels to charge a 12V battery; however, it is not quite as simple as connecting your solar panels directly to your battery. For starters, you will need a charge controller, which is a device that regulates the flow of electricity from the power source, meaning the solar panels, to the battery. These devices make sure the battery does not overcharge, which can lead to permanent damage.

In most cases, you will also need to connect a power inverter, which will convert the DC power your solar panels generate into AC power, which is what most appliances and electronic devices require.

To connect everything together, you will need to use the appropriate types of cables and connectors. For more information, consider taking a look at our Solar Panel Connectors Guide, which will tell you everything you need to know about using solar panels connectors and extension wires.

What are Amp Hours?

Understanding amp hours is one of the most important steps in figuring out your solar panel requirements for your specific battery. Essentially, an amp hour is a rating used to explain the amperage a particular battery can provide in one hour. Most deep cycle batteries will explain their amp hour rating by listing an Ah number. 

Once you know the Ah rating of your 12V battery, you can calculate the amp rating for your solar panels and learn how long it will take to actually fully charge your battery.

To calculate the current that your solar panels produce in amps, simply divide the power in watts by the voltage in volts.

How Many Solar Panels Would You Need to Charge a 12V 200Ah Battery?

It is important to remember that solar panels will not function at 100% efficiency at all times. Not only are weather conditions and the way the panels are installed factors, a certain level of efficiency is lost as the power flows through your charge controller and power inverter. Then, of course, most batteries do not hold a full charge, as their storage capabilities deplete over time. 

If, for example, you were using a 200Ah 12V battery and it was only able to store 80% of that power due to depletion issues, the battery might only be capable of storing 160Ah worth of electricity.

Given that a typical 100 watt solar panel can produce an average of roughly 30Ah per day (check 100 watt solar panel specifications), which is based on an average sunny day, you would need three 100 watt solar panels, or a single 300 watt solar panel to fully recharge your battery. Again, this assumes it is a sunny day and you are also using an efficient charge controller and power inverter.

How Long Does It Take to Charge a 12V Deep Cycle Solar Battery? 

Again, charge times are dependent on a variety of factors. The number and quality of solar panels you are using, the efficiency of the charge controller and power inverter, the quality and state of the battery, and, of course, the amount of sunlight the solar panels are able to absorb, will all play a role in determining how long it takes to charge your particular 12V battery.

However, in cases where the amp hour rating of the battery is matched with the amps produced by the solar panels, fully charging a drained battery will take between five and eight hours. Again, there are many factors that would impact the amount of time it would take. As you would expect, charge cycles are much slower on cloudy days, while sunny days almost always result in much quicker charge times. 

Buying Solar Equipment  

If you are on a budget, but would still like to purchase high-quality solar equipment, you should consider taking a look at the Renogy brand. Renogy has earned a solid reputation for offering high-quality solar equipment at affordable prices.

Whether you are looking to purchase additional solar panels, a more efficient charge controller, a reliable power inverter, or even purchase a new deep cycle solar battery, you will find exactly what you need by browsing our Complete Renogy Solar Collection. We carry a full range of Renogy products and offer them at the low prices that has made Renogy such a popular solar brand. 

Solar Power Generators:

If you are just starting out, you might want to consider a solar power generator, rather than a traditional solar power system that relies on a deep cycle battery for power storage. 

In simple terms, a solar generator acts as an all-in-one solar power station. The best solar generators will contain a high-capacity solar battery, an efficient power inverter, and an integrated charge controller. Rather than having to purchase each piece of solar equipment separately, or as part of a solar kit, you get everything you need in one convenient and portable package. Best of all, they can be charged quickly and efficiently using the same solar panels you would use to charge a standard 12V solar battery.

For more information about solar generators, we recommend reading our Review of the Goal Zero Yeti 3000X. Not only do we review the Yeti 3000X, we explain three alternatives that offer the same convenient solar storage, but at more affordable prices.

Final Thoughts 

While it is technically possible to use any size solar panel to charge a 12V battery, less powerful solar panels will take a significantly longer stretch of time to fully charge the batteries. The important thing is purchasing efficient solar equipment and positioning your solar panels in the best location possible.

If you have questions about choosing the correct solar panels for your existing battery, or you would like recommendations for equipment you can use to build an efficient solar power system, do not hesitate to reach out to us. We are always eager to help new solar enthusiasts get started!

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