Charging powerbanks with solar panels

Charging powerbanks with solar panels

This is not a brand new idea. However, it's a good opportunity to keep your power banks charged for the next recording, if you are far out in the fields.
We're talking about solar panels for hitchhikers.

They are available in different sizes and power classes. The size you need depends on your power bank's capacity and how many hours of sunlight your area gets. As a general rule, it's best to choose a power class that is one level higher than your power bank needs. 

These solar panels usually provide a voltage of 5 V and have USB-connectors.
For this example, let's assume you are using a 20W solar panel. Since power (W) is voltage (V) multiplied by current (A) - the math is easy.
Your power bank has a capacity of 20,000 mAh, which is 20 Wh written differently. 
So, if it's a bright and sunny day and the solar panel provides 20 W consistently, the power bank should recharge in an hour, right? - Well, not quite.
There are losses inside the solar panel, so it usually provides between 12 and 18 W.
Also, the charging circuits inside the power bank cause additional losses, and the batteries inside the power bank cannot be charged at full capacity all the time. 
Therefore, the actual charging time is usually about 3-4 hours. 
If in doubt choose the solar panel that is completly waterresistant, as it may rain, but be kind of sunny at the same time!

These numbers are changing significantly, if you are using solar panels with higher wattage.
BUT ... keep an eye on the output voltage of your panel. The voltage MUST be the one your power bank can handle!!! Double check and then double check again!

But yes! If you're out in the middle of nowhere, this will keep you going!

A 20-watt solar panel costs about 25 USD. 
They are also
... much lighter than an additional power bank!
... can recharge the same power bank several times!
... may provide an additional rain-protection for your gear