On Fri, Jun 25, 2021 at 04:19 AM, Jim Sheldon wrote:

Also what is that PC board device next to the battery? 

Thanks for the positive feedback. The design was intended to allow individuals to add batteries of their own preference. That little square slot can be snapped off if not required. 
The pics also don't show any wiring etc. 

That PC board is the Battery Management System (BMS). You need this because it prevents overcharge, over-discharge, short circuit and so on. The low-current versions are sometimes difficult to find. This one https://www.electromannsa.com/products/3s-4amp-18650-lithium-battery-charger-protection-board?_pos=12&_sid=665207520&_ss=r&variant=31826331205704 is a 4 Amp version, in other words it will protect if there is a short that draws more than 4 amps. Hopefully there are 2A versions out there but I haven't found them yet.
Without such a device you can theoretically extract 1000A from an 18650 for a short time, with disastrous consequences. I am sure you will find similar items at your locale. 
With the BMS in place, the side panel can be screwed into the main body and the discharge and charge occurs through the same barrel connector.  

(I'm not looking for arguments with battery engineers, and I am not an engineer. This solution has worked for me, if you have a better solution, let me know)