This carrying like a book, the charger deploys 4 panels (3 solar panels and 1 panel for recharging).
The "charging panel" consists of a small pouch to protect the device recharging of the sun and overheating rays. The model I have has two and taken to charge two devices simultaneously. Operation is simple, plug and head the signs of the sun.
Refill according to climatic conditions:
Grand soleil: Fast charging of two devices
Sun and some clouds: normal charging two devices.
Cloudy weather: fast charging of a device.
Only clouds: slow refill of a device.
RAVPOWER book with his 4 carabiners machine so you can fix it when, for example, there is the wind. The unit has charged all the devices I've tested (iPhone, iPad, samsung, android tablet).
Personal opinion: I think the product is still very compact despite the 3 solar panels. In the "book", the product is the size of a book medium in size (Smaller than 21x29x7).
It is ideal for camping trips, hiking or even at home for sunny days (ecological).
Lots of advantages (charging two devices at the same time, compact, efficient, 4 carabiners, resistant materials) and no disadvantage for now (apart from the size, but still pretty well contained).
I strongly recommend this product that satisfies me!
