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Can you Charge your Marine Battery with a Solar Panel?

Can you Charge your Marine Battery with a Solar Panel?

With the sun shining brightly and your marine battery undercharged, you are yearning to charge your battery and go for a nice boat ride.

But you don’t have a traditional battery charger available. You don’t even have a trickle charger. So what should you do?

You remember the solar panels that you have in your backyard. Solar panels have done a great job of saving you on your home’s electricity bill.

But could solar panels also charge your marine battery? If they could, how would you hook them up?

Let’s get those unused solar panels in from the backyard and find out.

Can You Charge A Marine Battery On A Solar Panel?

ECO-WORTHY 1.6KWH 400W 24V Complete Solar Panel Kit

There are still doubters, but you can absolutely charge a marine battery with solar panels. Solar power skeptics have existed for decades, but these are the same skeptics who are paying more for their home electric bills because they refuse to add solar panels to help power their homes.

The real question is: how effective will you be in charging your marine battery using solar panels?

The effectiveness of a solar panel for charging is measured in “full sun” ratings. Basically that refers to the length of time the panel has been exposed to full sun.

Full sun means the panel has been exposed long enough to form a sharp-edged shadow. At full sun level, 1000 watts of power are produced per square meter of panel.

Solar panels have been used effectively in small boats, sailboats, and racing boats. 

Panels have extended charge time. They have even eliminated the need for engine charging completely in some instances.

There are measurable environmental advantages as well. Solar panels have resulted in less carbon monoxide in the atmosphere.  

So the next time you are cruising along in your boat and enjoying the fresh air as it blows in your face and straightens your hair, remember that solar panels have helped make that possible.

How Many Solar Panels Do You Need To Charge A Marine Battery?

numbers of solar panels

But how many solar panels will you actually need? A deep cycle battery with a 100 Ah designation that is discharged by one-half of its capacity will take two solar panels to effectively charge it.

The panels would need to have a 100 watt rating, and the charging would take approximately one day.

With this principle as a guide, you can determine other charging times.

One hundred watt panels would complete the charge in approximately fifteen hours. Two hundred watt panels would complete the charge in about ten hours. Three hundred watt panels would take about five hours.

Keep in mind, the sun provides peak absorption for approximately five hours per day. So our three hundred watt panel would actually need a day to complete the job.

A marine battery has even been charged by solar panels with as low as five watts, although it took an entire year to complete the charge.

Obviously, you don’t want to wait that long, but if panels with only five watts are effective, little doubt remains that the task is possible.

The limitation is in the battery itself. You will notice in your battery manual that there is a maximum number of watts that it can handle. 

Batteries that charge slowly will still do so with solar panels.

What Size Solar Panel Do You Need To Charge A Marine Battery?

solar panel size

So if two solar panels are enough to complete the charge, what size should the panels be? 

Depending on the condition of your battery, and the weather conditions when you are charging, you may need to go as high as 120 watt-sized panels. 

Besides the panel size, positioning is also important. Be sure that your panels are positioned perpendicular to the rays of the sun. 

Avoid charging in a shadowed area. To increase effectiveness, ventilate the back of the solar panels

Don’t confuse your car battery with your marine battery. While the primary job of a car battery is to start the vehicle, a marine battery must keep working to keep the onboard components powered during the voyage.

Solar is so effective in charging marine batteries, that batteries which are completely dependent on solar energy are available for marine use. Many boaters have chosen to go completely solar by purchasing solar generators as well. 

Experience the natural wonder of solar power and see if you are hooked.

How To Hook Up A Solar Panel To A Marine Battery?

Newpowa 210W 24V Monocrystalline Solar Panel

It is easy to hook a solar panel to a marine battery if you follow a few simple steps.

First, mount your solar panels. If you have a roof or overhang on your boat, this is the ideal spot to mount the panels.

Next, use the zell protectors that are included in the solar panel package to connect the wires from the solar panels together. This will result in the formation of one wire.

Connect this wire to a solar charge regulator. A solar charge regulator has two purposes, it accepts the voltage from the solar panel, and it also provides an output voltage.

The output voltage that comes from the solar power regulator is used to charge the marine battery.

Finally, connect the charge regulator to the battery posts. Once the motor is running, you should not disconnect the charge regulator.

You can even charge more than one battery with additional charge regulator connections. Typically, you would have one battery to start your motor and another to power your onboard components.

Use the diagram included in the following youtube video to make your hook up even simpler. Following this diagram, along with the instructions that come with your charge regulator, will result in a hook up that is completed correctly.

Connecting solar panel & charge controller to boat battery

Can I use a 24 Volt Solar Panel To Charge A Marine Battery?  

Newpowa 210W 24V Monocrystalline Solar Panel Designed for 24V Charge System Off Grid Yes, a 24 volt solar panel can be used to charge a marine battery. This is primarily because solar panels provide constant current.

A concern arises when the power of the sun is diminished, such as on a cloudy day. In this case, consider using a power tracker.

This device ensures that the panel is providing its best charge, even when light levels are diminished.

You will find that there are two types of power trackers. You can choose a single or a dual axis tracker 

Single access trackers can be used to track the sun from east to west. Since dual axis trackers rotate on two axes, they are able to utilize the sun rays directly.

The makers of dual trackers claim that they improve power output by twenty to forty percent. By following the movement of the sun, dual trackers have greater exposure to the sun. So, in theory, they should produce more energy.

Regardless, a 24 volt solar panel can be used to charge a marine battery. It is up to you to decide if a power tracker is worth the extra investment.


So we have seen that a marine battery can definitely be charged by solar panels. But the sun typically provides peak power for only five hours per day. 

So an entire day of charging will not equate to twenty-four hours of constant charging.

You will need two solar panels to charge your marine battery. Be sure to arrange your panels perpendicular to the sun. Avoid charging where shade is present.

You will need a minimum of 100 watt sized solar panels to successfully complete the charge. 

So if you don’t have a traditional charger, consider using solar panels. Or switch to solar panels altogether, and help to keep the atmosphere clean.