Puzzle of the Week #458 - Phone Charger

This is my portable smartphone USB-C charger. It very handily and neatly docks onto the charging port of my android phone, without any need for a wire between them. To charge the charger there is a socket on the end as shown, which is also USB-C.

My question is, if you had a supply of chargers identical to this one, how many would you need to form a ring, where each charger was charging the next one in the chain?