New battery pack with solar assistance

I recently decided to upgrade my battery for a new Raspberry Pi 3 Piratebox (but this can apply to any Piratebox). I wanted a pure solar power solution but this was impractical, so I compromised with the
Aisla Solar Power Bank 20000mA/h which should power my rig for a long time.

What I like about it is that it holds a lot of power anyway but will also top-up using the built-in solar panel. This link to a short video shows it in action: it is facing a window with a lot of light and the blinking LED shows it is receiving a charge from the solar panel. The manufacturer states that the "solar panel charges very slowly" but I will need to test it out to see how long it takes. This is about the largest capacity (portable) power bank that I could find.

I have heard the built in panels are mostly for show some times not even connected to the battery so be sure to let us know how it turns out

I'd be interested in hearing how it works out. I started running one on a Nexus 4, and the battery was shot within a few hours (3-4). Though to be fair, poor battery life is why I finally kicked it in the first place.