How Long to Charge 12v Battery with Solar Panel?

by Malcolm Woods

Solar power is the best way to get free energy. With our current condition of the environment, we should really avoid burning fossil fuel. Now, I am not going to go over all the go green stuff.

You are here because you want to know how long it takes to charge a 12V car battery with a solar panel.

The short answer is, in most cases, depending on the size of the battery, it will take around 5 - 8 hours to fully charge a 12-volt car battery with a solar panel that can produce 1 amp of current.

For an effective charge, you need to make sure that the panel is directly facing the sun and no obstacles in between.

Now, the charging time will vary depending on the solar panel size and amp output. A large panel can charge a car battery faster than a solar charger with a small panel.

What Size Solar Panel Do I Need to Charge 12V Battery?

 What Size Solar Panel Do I Need to Charge 12V Battery?
What Size Solar Panel Do I Need to Charge 12V Battery?

A dedicated solar car battery charger can typically output 13.6V to 17.0V depending on the model you choose. They are made to charge regular car batteries and can also power any 12-volt devices.

For portable off-grid systems, these solar chargers are perfect as they can be used for RVs, small cabins, boats, and cars. Some even feature a converter to charge your smart devices.

Size-wise, a standard solar panel is 65×39-inches, which is used to charge a 12V 100-watt battery. The standard size for a commercial purpose solar panel is 77×39-inches.

How Not to Charge A Car Battery with a Solar Panel?

Okay, this part is dedicated to all the newbies out there that have never charged a car battery with a solar panel. This is a demonstration of how not to charge a car battery from a solar-powered charger.

First of all, you take the cable from the solar panel and make sure you don't plug it directly into the battery. And the reason you don't do that is because, although initially, you get a nice and safe charging voltage, which will be around 13.5 volts, it can very rapidly climb above that.

A car battery is meant to take in charge at around 12 volts. At these high voltages, the battery will start gassing.

It will start producing hydrogen and oxygen, and because of that, the electrolyte will start bubbling. If this goes on, eventually the battery will be destroyed.

So, what's the proper way?

The proper way involves the use of a solar charge controller. You can connect one end of the controller to the battery and then connect the other end with the solar panel.

This helps regulate the voltage so that it doesn't cross the safety limit. The charge controller monitors the voltage of the battery and does something called pulse width modulation.

With this controller, the battery will not go above the target limit or the safe float voltage. You can leave this setup connected indefinitely, and no damage will be done to the battery.

Can I Charge A Battery Directly from A Solar Panel?

If you are using a dedicated solar-powered car battery charger, yes, you can. If you are opting for a DIY method, make sure your charging system has a charge controller to regulate the voltage.

Can A 10-Watt Panel Charge A 12V Battery?

Yes, a 10-watt solar panel can charge a 12V battery, but the panel must be a 12V with a 10-watt specification. Every 10W 12V panel will have a peak voltage of 13.8V, which can easily charge a car battery.

How Long Will It Take To Charge A Deep Cycle Battery?

Batteries used in RVs, cars, and boats are called deep cycle batteries. They are designed to discharge and then recharge, and this goes on and on.

You can do it hundreds or thousands of times, and that's why car batteries last a long time.

Understanding Amp Hours

The batteries used in your vehicle will have a specific Amp Hour rating. They are usually 20 or 100 hours. Sounds complicated? Well, it's simpler than you think.

The amount of current that is supplied from the battery over a certain period of hours is called amp hours. For example, if you have a 350ah battery, it can supply 35 continuous amps for 10 hours or 17.5 for over 20 hours.


In a 6-volt 360ah battery, the total watt will be 2160 watts, which is 360ah x normal 6V. It can also be specified as 2.16kWh. To increase amp hours and voltage to the desired level; batteries are wired in parallel and/or series, just like a solar panel.

Are Solar Car Battery Chargers Any Good?

If you opt for the high-end models with dedicated controllers and maintenance features, it should be good enough. On top of keeping your battery healthy and topped up, they can also power other electronic devices.

How to Use A Solar Panel To Charge A Lead Acid Battery?

First of all, you need to get yourself a solar panel and a voltmeter. Make sure you get a standard size panel and avoid buying the larger ones.

When you connect the solar panel to the battery, you will see the voltage rise, and when it reaches to near 14V, it means the battery is fully charged.

When the battery is fully charged, remove the connection. You don't want to overcharge the battery or charge it too fast. Make sure to check the battery's owner manual to see how many amps your battery can handle.

If you are familiar with trickle charging, there are some solar chargers that are designed for the sole purpose of maintaining the battery's charge level.

They don't produce too much voltage to damage the battery. In other words, if you keep your vehicle on idle for too long, get a trickle charger.

Related: Our Reviews of Top Quality Silfab Solar

Final Thoughts on Solar Panel Buyers

There is no solid answer for How Long to Charge 12v Battery with Solar Panel. That's why you should understand certain terms like ah, watt, voltage, etc.

If you don't want to know all the details, get yourself a dedicated solar car battery charger and remove all the guesswork.

About Malcolm Woods

Malcolm Woods is a blogger who enjoys writing about technology and solar power. He has a passion for learning new things, and loves to share his knowledge with others. Malcolm is also an advocate for sustainable living, and believes that everyone has a responsibility to do their part in preserving our planet.

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