What Size Solar Panel To Charge a 100Ah Battery?

What Size Solar Panel To Charge a 100Ah Battery?

Many outdoor lovers opt for a standard 12V 100Ah battery when camping. Some still prefer the traditional lead acid batteries, while others opt for a 100Ah lithium battery instead for its multiple perks. Whichever one you get, you'd need a good set of solar panels if you plan on using solar energy to charge your power pack.

Now, when you say "good set of solar panels" the first thing that would probably come to your mind is overall quality and performance. You want something that can withstand outdoor conditions, easy to install, and preferably with a charging efficiency of 15% to 21%. While this is understandable for optimal charging, a lot of solar power users forget that these factors are not all there is to it when it comes to choosing solar panels.

Whether you have fixed solar panels, flexible solar panels, or solar mats/solar blankets, another thing you always need to take into account is their size. You could have the best solar panels and still not achieve maximum charging efficiency because you got the wrong size for the battery pack that you have.

In fact, sizing your solar panels should be one of the first steps you need to consider before all the extra features you want. Luckily, it's quite simple to know what size of solar panels you need as well as what you need to keep in mind if you're going to switch to solar soon.

What Size Solar Panel To Charge a 100Ah Battery?

Actually, you can charge a 100Ah battery with a 3-6 watts solar panel. However, this will take ages and can be an inconvenience if you're off grid camping or anywhere without access to a mains power. You'd need something with a higher wattage to reduce the time you need for charging and this can easily be determined by this formula:

Amp hours/peak sun hours = amps

Amps x battery voltage = your solar panel's size

Given this, if you have a 12V 100Ah battery and you're getting around 5 peak sun hours in your location per day, it's safe to assume that you would need a 240W solar panel to top off your power pack effectively. It's always safe to go a little over what you initially need with solar energy, so a 300W solar panel would probably be your best option here.

It's also up to you if you want a single 300-watt solar panel, two 150W solar panels, or three 100W solar panels. You might need to size up your RV for this or check your budget to see which set-up would be best for you and of course, choose a reliable solar charge controller as well, like an MPPT regulator.

What Other Factors Affect Charging Efficiency?

If you're done sizing up your solar panels, it's time for you to know what other things to look out for which may impact your charging performance.

Solar Panel Age

Solar panels typically last for an average of 25 years before they show signs of decline. They would still be able to generate power but won't be as efficient as when you first had them so if yours are particularly old, you might want to observe them during the charging time.

Mounting Orientation

Where your solar panels are facing impacts their efficiency as well. Make sure they catch the sun for long hours and face them where they'll get more direct exposure. In houses, panels facing south mostly generate more electricity, however, this may be different for RVs which are constantly moving.

Solar Panel Shading

Shading is one of the biggest concerns when charging with solar panels since this can result in power loss. To prevent this, some solar cells install bypass diodes, providing a path for the current that allows the string of solar cells to continue generating energy at a reduced voltage.

Weather Condition

Unfavourable weather such as a cloudy or rainy day will decrease the efficiency of your solar panels and increase charging time. However, there is also a misconception that high temperatures are better for your panels, which is not true as it can reduce their performance due to high resistance. This can be countered with thermal management though, which also improves the lifespan of your solar modules.


Solar panel maintenance includes regular checking and cleaning. Cracks and dirt build-up also affect quality and may even reduce the service life of your panels over time. Make it a habit to frequently inspect them and ensure you have enough knowledge on how to clean your solar panels to enjoy maximum output.

All set to buy your camping and RV solar panels? Visit Outbax now for a wide range of them! Our solar panels for sale are all shade-tolerant and have bypass diodes to deliver energy even in unfavourable weather conditions. We also have a range of LiFePO4 batteries that will make the best solar batteries for pairing with your solar panels, including bundle sets complete with solar charge controllers!

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