When poking around the internet for battery packs, this item from TalentCell piqued my interest due to its ability to supply 12V in an affordable package.
The case is put together with screws. It’s begging to be opened up to discover what’s inside. Thankfully, the contents are exactly were as advertised on Amazon. Inside are 6 18650 batteries in a 3S2P (3 series, 2 parallel) configuration.
A board with the DC I/O jack, the USB jack, an on/off switch, and LED voltage indicator lights. 
The backside of the board. It appears to be generic, as do the cells.
Each 18650 cell has a nominal output of 3000mAh and a voltage of 4.2V when fully charged. Put three of them in series and you get 12.6V. Put two groups of these three cells together and the capacity doubles to 6000mAh.
The cells are charged through a BMS, or battery management system. As you can see below, I had to peel back the tape holding the cells together to gain access to the BMS.
The BMS balances the groups of cells for longevity and safety.
So far, this battery pack has held up well. I don’t have any way to verify the amp-hour capacity of the cells, but I used it for a month as my primary station battery supply and it needed topping off after three weeks of daily usage.
This TalentCell battery pack continues to see regular usage in my shack, especially since I have made the DC barrel connector on my MTR3b compatible with it. Now I have one battery pack for all my SOTA and POTA radios.
Amateur Radio Station WB0ISG 