I also have a Ramoss 20,000mAh, and love it.
Yes it's heavy and takes long to charge... BUT, it IS 20,000mAh!!! That's around 6 charges for a modern phone.
I got my wife a sailing 6 to get through the rolling blackouts. Now she uses it pretty much exclusively to charge her iPhone with the added bonus of no power surges and it cuts out when it's fully charged.