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A Guide on Charging a phone with a Solar Panel

We are constantly on our phones checking for messages, browsing the internet, gaming and watching videos.  These activities drain your phone and you will need to recharge the battery more than once in a day.  A phone battery can run out at inopportune times and you may not have access to a power source or even a charger. A solar panel is a great option for powering your devices in emergencies, off-grid and portable uses. But can you charge a phone battery with a solar panel?

The good news is that you can charge your phone with a solar panel but there are some ground rules. The size and the wattage may vary as a panel that is too small may charge your device too slowly and a panel to large may be too bulky or may not work with your device. Solar panels are conventionally made for powering households. You should never directly charge your phone using these solar panels as they may damage your device.

foldable solar panel

A solar panel charger rated at 20 watts and 5V will charge your device directly. We have listed these solar cell phone chargers in another article but you can make any solar panel work using the right configurations.  We look at these later in the article. But first let’s look at the ground rules.

1. Never Directly Charge your Smartphone Using a Solar Panel over 5v

A phone battery is a lithium-ion type of battery that come in a cell with a 3.7 V.  A 5V voltage is the recommended voltage for charging and is the output voltage for most chargers. A higher voltage is likely to damage your phone’s battery.

If you are using a solar panel charger to directly charge your battery make sure it does not exceed this voltage.

2. Ensure the Ports are the right one for your device

A Solar Panel Charger can come with either a Micro USB, Type C or USB Ports. Depending on the type of phone you use it is important to check for compatibility. These ports also have different outputs and may not be fast charging ports.

3. You don’t have to fully charge your battery

Solar panels are dependent on the availability of sunlight and sunlight may vary time to time.  You will most likely find the best times to use the full capability of your solar panel between 12 and 4 pm depending on cloud cover.

Even if you happen to get 30 mins to an hour you actually don’t need to fully charge your phone’s batteries. The Lithium-ion batteries in your phone will be at optimum between 30 to 70% charge. Even when buying your phone the battery is usually charged up to 40% and is stored at that capacity.  High voltages  and draining the battery cause it to age faster as it goes through its “cycles” faster.

Charging your phone in short bursts throughout the day is probably the best way to keep your phone going in both the short and long term.

4. Fast Charging will only work to a certain percentage

Continuing from the previous point a phone battery has two phases of charging; the first phase of the fast charge and the second phase of the trickle charge. The battery will charge quickly up to 70% and when it enters the second phase of trickle charge it will take longer to  get to 100%.

So when using a solar panel if it happens to be charging slowly and the battery has already reached 70% just know that this is normal and not because of any issues in your set up.

5. Lithium-Ion Batteries in your phone have overcharge protection

You don’t have to worry about overcharging the battery as it has in built IC chip that cuts off the charge current. But this is for the small 5v charger. For a bigger solar panel you must use a charge controller which we talk about later.

6. Avoid Extreme heat and Cold

When using your solar charger to charge your phone you only need to expose your solar panel to the sun and not your phone.  Direct sunlight will cause your device to overheat. The operating temperature of a lithium battery is between 32 and 95 degrees Fahrenheit. 

Most modern chargers will come with pouches with a cable from the solar panels. This will allow you to place the phone away from direct sunlight while charging.

We’ve looked at using a 5v solar charger to directly charging your cellphone battery. Now let’s look at other set ups that use a solar panel to charge your devices including your battery.

Using a Solar Power Bank

A Solar power bank charger has a battery pack alongside the solar panels. You don’t have to hook your phone directly on the solar charger and you only charge from the battery bank. In most types the solar panel is quite small and solar charging is only as a backup option. It is important you charge the bank via an AC source. 

Use Charge Controller

A charge controller is the heart of the solar system.  It ensures that the batteries is safe and the system operate optimally. You should never connect a battery to a solar panel without a charge controller.  It protects the battery from overcharging, the battery reverse charging at night and even under charging the battery.

Charge Controller with 5V USB Output

Some controllers have a 5v USB output that you can connect your cable to and charge your phone.

A MPPT controller can even improve performance during cloudy days and increase the amps coming from the panels by looking for the Maximum Power Point.

AC power from an Inverter

An inverter is connected to the battery and converts the DC power from the batteries to AC power.  With AC power you can directly connect the phone charger to the AC output and charge as you would with electricity.

In this scenario the solar panel charges the battery and the inverter provides AC power to charge your phone.

Portable Power Station

A power station combines a lithium battery, inverter and controller all into one.  The addition of a solar panel makes this system be referred to as a solar generator.

A power station can provide enough power to charge your phone, laptop and even power a mini fridge.  It all depends on the size of the battery bank within it.