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What Size Solar Panels To Charge 100Ah Battery

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Pairing solar panels and solar batteries is one surefire way to power any outdoor adventure. Whether you're going tent camping or hopping in your RV to go someplace nice, this combo will ensure that you never run out of power, especially on a sunny day. Usually, campers use a 100Ah battery to pair with their solar panels. Given this, among the big questions you have to consider is: what size of solar panel do you need to charge a 100Ah battery?

First things first-the main function behind this setup is that your solar panels can generate energy from the sun during the day and transfer it to solar battery storage for later use. Now, solar panels come in different types. We have fixed solar panels or flexible solar panels which are usually used for homes and RVs. There's also an option to go for portable solar panels especially if you don't go camping that often or you only have a handful of appliances to power. 

However, aside from the type of solar panel you'll be using to charge your battery bank, the more important factor to consider is your solar panel's size. You want to make sure it's sized properly to be able to effectively top off your power pack and avoid issues with insufficient power, especially in an off-grid camping setup. Read on for a little guide on choosing your solar panel size and other items you will need when installing your solar power system.

What Size of Solar Panel Do You Need to Charge a 100Ah Battery?

You can actually charge a 100Ah battery whether it's a lead-acid or lithium battery with 5W-10W solar panels but this could take very long. You will need a bigger power output for a faster recharge plus, the number of hours it will take to fully top off your battery pack is also dependent on its state of charge and the solar charge controller you're using. For example, if you have a lead-acid battery discharged at 50%, this could take a shorter time to charge compared to a fully discharged lithium battery with a fast-charging feature. 

This lead-acid battery at 50% capacity can take 12.5 hours to fully charge if you're using a 100W solar panel and under favourable weather. If you want to be able to recharge it within a day, better go for bigger-sized panels such as a 200W solar panel. This calculation may also vary if you're using a different type of battery like an AGM battery or LiFePO4 battery. Every power pack has different charging features with some charging at a slower rate than the others and vice versa. 

How Many Solar Panels Are Needed To Charge a 100Ah Battery?

Determining the number of solar panels you will need to charge a 100Ah battery is not confined to these two components alone. You need to have an estimate of your peak sun hours per day as well. Luckily, there's an easy way to calculate this. You just need to divide your battery capacity by the number of peak sun hours and multiply the amps you get with your battery's voltage. 

For example, if you have a 12V 100Ah battery and 5 hours of maximum sunlight exposure in a day, the computation would go like this:

100Ah / 5 hours = 20 amps

20a amps x 12V = 240W

Since you'll need a 240W output for this, it's up to you if you're going to get two 120W solar panels, three 100W solar panels and so on to be able to charge your battery. This is dependent on the space you have for installation as well, so make sure you buy solar panels with a high-efficiency rate so you maximise whatever roof space is available to you.

What Is the Importance of a Solar Charge Controller?

A solar charge controller is a type of switch that regulates the current generated by your solar panels which will then flow into your battery. Usually, 12V solar panels generate more voltage than what your battery needs and this can cause overcharging. Your solar charge controller or regulator's main job is to ensure that the current transferred into your battery is compatible with its original voltage. 

Once your battery is fully charged, your regulator will also automatically shut off the supply of electricity. When your battery is not being charged during the evening, the solar charge controller continues to function to prevent a reverse current from flowing back into the panel and discharging the battery even when it's not in use. 

There are two types of solar charge controllers: the Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT) regulator. A PWM regulator works by sending continuous long pulse charges to the battery and sending shorter ones after it's fully charged. This type of controller is often recommended for smaller solar panel operations that won't need to use your system's maximum power output. 

An MPPT solar charge controller, meanwhile, tracks both the solar panel's output and voltage level required by the battery to match them for an optimal charging process. This regulator is considered more efficient and is naturally priced higher since it can handle solar systems and batteries of different voltages.

Solar charge controllers are not needed in every kind of system but are highly recommended mainly to protect your battery. The general rule here is that you can skip installing the regulator if you have less than 5W per 100Ah of battery capacity. In some cases, you can also go without a solar charge controller for lead-acid batteries topped off by low-current charging. 

More from Outbax

Get the best quality batteries and solar panels for a wallet-friendly price tag. Here at Outbax, all our power packs are LiFePO4-based and are suitable for deep cycle applications for superior performance. They're available in different voltages and capacities too, perfect for all kinds of outdoor adventures. As for our solar panels, they come in a variety of types as well plus, we also have solar panel accessories to help you out with installation or quick fixes. 

All these camping gear are shipped free within Australia, so hurry and get one for your next outing. If you're not a fan of complex setups, you can also have a look at our award-winning inverter generator section. They're handy, fuel-efficient, and of course, affordable too!

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