Sourcing electrical connector, thick cable to thin?

[DickieT]

I'd wrap solder and heat shrink.

Yep, +1 for wrap and solder. Unlike most of the other suggestions it is, easy, cheap and 99.9 % reliable. A soldered and heat shrunk wrap joint is impervious to moisture. Soldering is not a difficult black art skill. If uncertain ask somebody to show you. The money spent on some of the other suggestion would go a long way towards a decent soldering iron and it will stand you in good stead for years to come. It will save you from all the chocolate box horrors I have had to fix over the years, these often causing their owners hours of grief. I have joints made this way (albeit with sleeving - pre heat shrink days) made 30 years ago and still fine.
(Friendly) rant over.
Good luck.

 

[nigelmercier]

All suggestions sound rather overkill to me. Presumably the existing 'thick' cable is stranded. I would reduce the existing cable by removing enough strands to fit the largest ring-crimp which will comfortably fit the new charger. (ideally gradually over several inches to reduce fatigue). Then suitably insulate.

+1