What to Look for In A Solar Battery Charger

What to Look for In A Solar Battery Charger

By Renogy UK
Renogy UK
renogys blog Mar 2nd 2022

Want to keep your electronic devices connected while you’re off the grid? Be able to recharge your phone while away from home? Or switch to clean, renewable energy for your car or RV batteries? A solar battery charger is what you need.

A solar battery charger allows you to harness the energy of the sun for your personal electronic devices. It can quickly become an essential part of many solar power set ups. In this article, we’ll dive into how solar chargers work, how to choose a solar battery charger, and key specs for a portable battery charger.

How do Solar Chargers work?

A solar charger is a device that uses sunlight to generate electricity. It’s made up of a solar panel and an external battery pack - together they harness energy from the sun to charge your electronics.

A solar charger can be used to charge all kinds of electric devices. It can charge a laptop, car or RV batteries, personal fan, light - and many people use them for charging a phone. The size of the solar charger varies greatly too, ranging from a handheld device - perfect for when you need something lightweight and only have small electronics needing charge - and can be much as large as a table for charging car or RV batteries.

The solar charger can’t directly transfer electricity into these devices, so it stores electricity in the power, making it available for later using something called a charging supercapacitor. This charging supercapacitor is a life-saver when the sun has gone down, or your summer camping trip ended up with a lot of rain. It means you can charge your devices when you need them, not just when it’s a sunny day.

Think of a good solar charger as kind of like a traditional rechargeable battery. It stores power until you need it, and only uses the energy you need - anything leftover waits until you plug another device in.

So… how do solar chargers work? Well in a nutshell, when the sun hits the solar panels in the device, the solar cells generate electricity. Then that flows into a lithium ion battery pack, which then stores and regulates power to your devices when you have them plugged in.

Want to know the technical details? Well here goes.

The sun strikes the surface of the solar battery charger and is absorbed by the individual solar collars that make up the solar module. Then, photos from the sunlight activate electrons to create an electric field. That’s where the charger’s voltage comes from. The electrons travel to the solar battery charger, which stores the electricity until you are ready to charge your electronic device.

Some devices use direct current electricity to charge their batteries, while others use alternating current electricity. If your device uses direct current electricity, a charge inverter will switch it to alternating current electricity - a more usable form.

The final step is when you plug in your electronic device, and electricity is expelled out of your solar battery charger and into the device.

If that sounds a little complicated think of it like this: All you need is the sun, your solar battery charger, and you’ll be able to recharge devices without a worry.

A common question people ask is - can a solar panel overcharge a battery? The answer is yes, it can. To avoid this you’ll need to have a solar charge regulator connected - or have a small solar panel that only delivers trickle current and maintains a float charge. If you would like to have your solar panels charging all the time (for example, with a solar car battery charger), it would be wise to invest in a solar charge controller. Solar charge controllers regulate incoming solar power to maintain batteries and prevent overcharging.

Do solar battery chargers really work?

Now that we have established how solar battery chargers use the sun to generate electricity and store power, you may be wondering - but do solar battery chargersreally work?

The answer is yes! But there are some limitations you should be aware of, depending on your charger needs. Solar battery chargers can take some time to charge your electrical devices. Practically, the best devices to charge using a solar charger are small electronics.

You can use solar battery chargers to charge your phone. But keep in mind the solar battery charger will be slower than your phone’s original charger - and you’ll need to ensure your solar battery charger has the right USB port to connect to your phone’s charging cable.

Solar battery chargers can be used to charge a laptop, but the charging time can be long. They can also be used for small devices such as a light or fan.

Solar battery chargers can be used to charge car and RV batteries, but this can take multiple days to charge. In this circumstance, you could consider using them alongside portable solar panels for RVs.

How to choose a solar battery charger?

Now you’re probably wondering what to look for in a solar battery charger.

First of all, there are a few solar panel options available. You can purchase the solar panels only (either rigid or semi-flexible), which can technically directly power a device - although we definitely don’t recommend it. That’s because the solar panels may not contain any circuitry to regulate the flow of electricity into your device. Plugging your device directly into it could damage your device. If you are set on a direct power connection, be sure to purchase solar panels with a regulated USB output for small electronic devices.

We recommend that instead, you purchase solar panels with integrated storage batteries or solar panels with separate storage batteries. We’ll cover the key specs for your portable battery packs in the next section.

Here’s what to consider when choosing a solar battery charger.

Surface area

If you are already a fan of using solar power, you’ll know that when it comes to solar panels - size matters. If you’re not already a fan of solar power, we hope we can convince you to start!

Essentially, the bigger your solar panel is, the more sunlight it collects and the faster this solar energy is converted to power stored in your battery. Smaller solar panels definitely have their benefits. They are lighter and easier to pack, carry and attach to your backpack, kayak or bike - but they do take longer to charge a battery.

A larger solar panel is also best when you might not have great exposure to the sun. So if the area you’ll be using it in is prone to cloudy days, or you’re traveling in winter when there’s less light, investing in a larger solar panel might be a wise choice.

You might be surprised to learn how vastly charge times can change for the same battery. Depending on the surface area of your solar panels and the weather conditions, your charge time could vary from 4 to 16 hours of sunlight!

If you’re going to an area and have high power needs, you may consider using a solar panel to harness energy in addition to your solar battery charger.

Output capacity

Think about how much you might need to use your solar battery charger and its output capacity. Solar panels are rated in watts - the higher the number of watts, the more electricity generated. So if you have a high need for electricity, it’s best to invest in a solar battery charger with a high number of watts.

You can calculate the current in amps by dividing power in watts by the voltage in volts. Take the example of 12 volt (12V) solar panels rated at 100 watt (100W). When you measure the output, the voltage will be about 18 volts (18V). Watts equals volts times amps, so amperage will be 5.5 amps. This panel will produce 5.5 amps per hour (ah).

To calculate how many solar panels it takes to charge a 100ah battery, you can use the same calculation. Charging your battery at 12 volts (12V) and 20 amps will take five hours to charge a 100ah battery. Multiple 20 amps by 12 volts and you get 240 watts - that’s the size of solar panel you would need to charge a 100ah battery. You could choose to use a 300 watt solar panel, or three 100 watt solar panels.

Semi-flexible or rigid panels

The solar panels you choose will depend on what type of trip you’ll be using them for. If you’re tight on space, or on the move, consider semi-flexible solar panels rather than rigid panels. Semi-flexible solar panels can be rolled or folded, and many are actually larger than rigid panels when opened up. You may like to even invest in an attachment for your solar panel, so they can be securely fastened to your backpack, bike, kayak or camping solar panels for your tent.

Key Specs for Portable Battery Packs

As we mentioned previously, you can choose from an integrated storage battery or a separate storage battery. The integrated storage battery is all-in-one, and has everything you need to plug and power up. Choosing a separate storage battery gives you the flexibility to leave the solar panels behind while you take just the battery, but you will need to pay careful attention to the output connector.

Whichever you choose, it’s important not to overlook the specifications of your portable battery pack when looking for a solar battery charger. Of course, solar panels are very important - but the battery determines if you can actually recharge your device!

Read on for some of the key specifications you should consider for your portable battery pack.

First of all - and maybe the most important - storage capacity. This is how much charge the battery can store for use later on your electronic devices, before it needs to be recharged.

You can get an idea of how many recharges you have available in your portable battery pack by comparing its storage capacity to the battery in your device. This may be stated in milliAmp hours (mAh), Amp hours or watt hours (wh). You can convert watt hours to milliAmp hours with this formula: (wh/Volts) x 1000 = mAh.

To be able to recharge your device, your portable battery pack needs to have enough storage capacity and output voltage to move energy into the device. To check if you have enough, find out the storage capacity of the battery in your device. It’s simpler if your device uses AA batteries - for other devices like your cell phone, read the technical specs to find out.

Now for a little more math… It’s important to remember that the output of your solar battery charger (measured in volts) has to equal the input battery voltage of your electronic device. If it’s lower you might end up accidentally draining your electronic device’s battery rather than charging it!

Most portable battery packs can easily charge your cell phone, but you’ll need to invest in something with a much higher storage capacity to recharge your laptop. As a general guide, a small electronic device that can be charged with a USB cable (like a cell phone) needs a 5 volt (5V) output rating. Larger electronic devices like a laptop could need 12 volts (12V) - 24 volts (24V). Think about what you need to charge before purchasing your portable battery packs.

It’s also important to consider the size and weight your portable battery pack will take up. The bigger and heavier they are, the more storage capacity they have. Do you need a lot of power? Or just something to provide an emergency charge? Establishing your power needs will help ensure you’re not carrying around extra weight for nothing.

Tip: If you purchase your solar panel and battery separately, check its output connector and how to connect to a separate battery pack. Your options could include a USB, connector, or DC output with voltage control.

Extra tip: Always fully charge your devices before heading off on a trip. You want to use your portable battery packs to recharge when you need it, not because you forgot to plug it in at home!


A solar battery charger is the ideal addition to your solar setup. It will allow you to recharge your electronic devices just by using the power of the sun - revolutionizing your trips off-grid in a tent, bike, or kayak or by foot. With the right set up, you’ll never need to worry about being without your essential power again!

Check out the Renogy website for a variety of chargers to meet your solar powering needs.