I received the eBay Solar Power Bank yesterday. It came with zero charge. I plugged it into a charger and it was passing through. I let it charge overnight - all charge lights were steady. I unplugged it from the charger and get no power from the USB ports - so something is wanked in it apparently.
I decided to open it up and it has two batteries in it. I can see faint printing on them stating 3500 mAh - so it seems the advertised 80K mAh is more than slightly optimistic.
Also, it is sold as waterproof and it is not sealed in any way inside or out.
If the sun ever comes out here I might see if there's voltage coming from the solar panel. I'll be contacting the seller, but I suspect the return policy will be more trouble/cost than it's worth. < update> free to return, so it's going back. Don't know if there will be a plan B.