Charging A 12V Battery With Solar Panels? What You Need To Know


12V Battery With Solar Panels

When you install a solar panel system in your home or office, you will almost certainly connect it to batteries. It allows you to run appliances without incident, even at night. If you intend to run an entirely off-grid solar panel system or RVing and camping, then having an idea of what type of panels will charge up your batteries is beneficial information. However, you can only use such batteries if they are the right size for your solar array.

If you’re using the standard 12V battery and want to know how many panels will charge up or what size solar panel to charge 12V battery, then you’re in the right place. Keep on reading for more information about solar panels for 12v batteries.

An Overview Of Deep Cycle Batteries

Deep-cycle batteries, as opposed to car batteries, are designed for short bursts of power and then recharged or replaced by the vehicle’s engine and are intended to provide a consistent stream of electricity over their lifetime.

Deep-cycle batteries, typically used with solar panels to collect and store power generated by the sun for future use, can provide energy continuously over long periods—with proper care and maintenance. Most manufacturers recommend that you discharge a deep cycle battery no more than 45%, but it can be safely discharged up to 80%. Going beyond this point may decrease the life of the battery.

Numerous varieties of deep-cycle batteries are commercially available today. Among the most common choices are:

  • Lithium iron phosphate
  • Flooded lead-acid
  • Sealed lead-acid

Where Can I Purchase Deep Cycle Batteries For Solar Panels?

Because solar panels require specific deep-cycle batteries, it can be challenging to find them. Fortunately, most solar panel manufacturers and suppliers offer these batteries in most cases—they’re either included in your solar kit or sold separately.

You can also find other varieties of deep-cycle batteries, such as 24V and 48V models. Due to their high efficiency and long life span (which makes them ideally suited for use with solar panels), you are likely to encounter many different types of these batteries at either a solar panel supplier or a battery supplier.

How Much Time Does It Take To Charge A 12V Deep Cycle Solar Battery?

Even if you have a powerful enough solar panel to charge your 12V deep cycle solar battery, you may still want to know how long it will take. Unfortunately, the time required to charge a 12V deep-cycle solar battery is highly variable.

The primary factor is the current weather in your area. A typical solar panel will charge an average-sized 12V deep cycle solar battery in 5 to 8 hours, depending on the weather. On a sunny day, the battery will charge much faster than if it is cloudy. Similarly, your batteries will charge faster in the summer than in the winter.

What Size Of Solar Panel Is Required To Charge A 12v Battery?

Even if you have a high-performance 12V deep-cycle battery, it will only be useful if properly charged. To that end, you must use appropriately sized solar panels capable of charging your 12V batteries. Fortunately, you can charge your 12V battery with almost any size solar panel, even if it takes a long time.

However, connecting your solar panel to a 12V battery will not charge it. Instead, a charge controller will be required to provide regulated electricity from your solar panels to your 12V batteries. Such charge controllers also protect batteries from problems like overcharging.

The solar panel size you need is determined by two variables: The capacity of your battery (in amp hours) and how long it takes to charge in peak sun hours. Let’s go into detail.

Battery Capacity

12V battery capacity is typically expressed in amp-hours (Ah). The number is printed on your battery’s specification sheet or engraved on its outer surface. The total capacity and voltage of a bank (of batteries) can be calculated if you want to know how long it will run any given load before recharging is needed.

To better understand this, consider a 100-watt solar panel connected to a battery. If you use a 12V solar panel rated for 100 watts and operating at peak efficiency, the actual voltage output will be around 18V. As a result, a 100-watt panel will provide approximately 5.5 amps of electrical output because power wattage is the product of voltage and current. To put it another way, a 100-watt solar panel will generate 5.5 amps per hour.

Discharge Rate

Calculating your discharge rate while batteries are charging is crucial if you plan to continue using the batteries. You can make sure your solar panels are strong enough to run your appliances and charge your batteries by estimating the amount of energy used by your constantly running appliances, such as your air conditioner, lights, and refrigerator.

Calculating wattage from amp-hours and voltage allows you to understand how much power a battery can store. If your appliances consume 300 watts, for example, the same battery could run one of them for about 12 hours before it was drained. You can calculate how much power various appliances consume by multiplying the voltage and amperage of the device. A 3-amp appliance with 120 volts will use 360 watts (3 x 120 = 360).

When you know the appliance ratings, you can calculate total energy use. We can estimate solar panel size by calculating the expected discharge rate for each load.

What’s Next?

Let’s take that same 12-volt, 300 amp-hour battery (with a 3600 watt-hour capacity), and assume an expected daily discharge of 2800 watts. Those numbers will help us figure out how big our solar panels need to be to keep our appliances running—and then fully charge the whole system when night falls.

You need 2800Wh of power to run these devices on their own. If your solar panels provide an excess of this amount, you can charge the batteries for use at night or when it’s cloudy.


After going through this guide on what size solar panels you need to charge 12V batteries, you should be able to easily select the right type of panels for your needs. You can also find information about common types of 12V batteries used with solar charging systems in this article.

It can be daunting when you first start researching battery options. You must know the difference between amp hours and volts, sealed lead acid from flooded—there are many considerations. You can get a battery bank that works for you and your family by doing some basic math to determine your energy needs and reading up on the various battery options available.

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Preeti Shah is a person who loves checking out different styles and designs of houses. She took interior designing in college and is practicing in the field of home improvement for five years now. In her spare time, she is usually searching the web for interesting and fascinating home designs.


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