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

Written by Eddie B. Robinson / Checked by Justin Tucker


Over the years, solar panels have become a popular alternative energy source, especially now that people have become more aware of the dangers of climate change. If you want to make a DIY solar system, it’s best to start with a solar system battery charger.

Most people like to use a 12V car battery with their simple solar system, but you might be thinking, “How long to charge 12v battery with solar panel?” The truth is, there are a lot of factors that can affect the energy production of your solar panels.


How Long To Charge 12V Battery With Solar Panel

First of all, you need to know how much current your battery can give every hour. You can see this in the specification on your battery provided by the manufacturer in terms of amps per hour or Ah. If you don’t see it, you should ask the seller since it will be hard to calculate the number of hours it will take to fully charge.

So for example, if you are using a 12V charge car battery with 100Ah, first we have to find out how much power it can provide. So multiply 12V by 100 Ah, and we get 1200wH.

Let’s say that your solar system is using a 200-watt solar panel. So, divide 1200wH by 200W, and you will see that your battery will need 6 hours of sunlight to fully charge.

To let you understand better, here is the equation:

12V x 100Ah = 1200 Wh

1200Wh / 200 W = 6 hours

Now, this is just assuming that you have the perfect condition for your solar panels. The label may say that it can produce 200W of energy, but it may not be able to provide that same energy all throughout the entire day.

The energy on the label was only achieved in a lab setting where they simulated the perfect condition, which, we know, is not something we can always get in the real world.

Some of the factors that can affect the energy production of your solar panel are cloudy days, shade, dirty panels, seasons (different seasons mean different angles for the sun), time of the day (there is less sunlight in the early hours of the day and late afternoon), and even temperature (your solar panel becomes less efficient when it gets too hot).

So with all of these factors, it is safe to assume that you may need another hour or two for your battery to be fully charged.

How To Charge Your Battery Properly


If you are new to solar panels, then it is important that you learn how to charge your battery properly. And let’s get something straight, plugging the cables from your solar panel directly to your battery is not the right way to do it.

Even if you are using a small solar panel to charge 12V battery, a very sunny day may produce more voltage than the safety limit of your battery, damaging it and making it useless. So to prevent that from happening, you are going to need a solar charge controller.

Solar charger controllers make sure that whatever voltage your solar panels have, what goes inside your battery will not pass the safety limit, which in our case is 12V. It will also prevent your battery from overcharging (meaning you can leave it alone) and discharging when there is low sunlight.

Electrical current flows from a higher voltage to a lower voltage, and low sunlight can make your solar panels have a lower voltage than your batteries, making the electricity that you have gathered flow back. Solar charge controllers prevent this by acting as a valve and letting electrical current flow in one direction to your battery.

Should You Consider What Type Of Battery You Should Use

Of course. The functionality of your solar system will largely depend on the type of battery that you will use. There are mainly two types of batteries that you can use for a solar panel system, the lead-acid battery and the lithium-ion battery. Each will differ in cost, capacity, voltage, and life span.

When looking at batteries, the first thing that you should look at is their capacity. The size of your battery will determine how many appliances you can power with your solar system.

Second, check out the life cycle of your batteries. Batteries can be expensive, so make sure that what you are using is a 12V deep cycle battery. This will make your solar system last for a long time without replacing your battery too often.

That being said, when it comes to the type of batteries, lithium-ion batteries will always beat lead-acid batteries. Why? Because lithium batteries can be charged with a higher current, unlike lead-acid batteries, which can overheat. Lithium batteries can even be discharged up to 80% of their capacity with no problem at all.

Most lead-acid batteries can only be discharged up to 50% or they will get damaged, significantly lowering their life cycle. Their charging speed also drops when they approach full capacity, unlike lithium batteries.

This makes lithium batteries more expensive, but the investment in the end is worth it.

Determining The Size Of Your Battery


As said before, the size of your battery will determine how many appliances you can power. So before you go to the store, you will have to determine how many appliances you would like to be powered by the battery.

Calculate the wattage of each device and multiply it by the number of hours it is used. So, for example, if you are using a 2oo watt TV for 3 hours a day, you are using 0.6 kWh per day on that device.

What Type Of Solar Panel Should You Use

There are three types of solar panels: Foldable, fixed, and flexible.

If you are using your battery as a portable generator, choose a foldable solar panel to make it easier to move around. Fixed and foldable solar panels are good if your solar system is just stationary, with foldable solar panels being easier to set up.

But regardless of the type, make sure that when you are solar charging, at least use a 100 watt solar panel for 12 volt battery. If you use something lower, it may not properly charge the battery.


Today, people have gotten into the trend of using alternative energy. Almost every house or business establishment you will see will have solar panels on their roof, which is good.

If you want to get into the trend, you can start by using your solar panel to store energy in a 12V battery for off-grid purposes. But it is important to know how long to charge 12v battery with solar panel so you know when you can use it. If you forget, just come back and read this article.

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