[Jason] shows us how we can use a PPS-capable USB-C charger for topping up our Li-Ion battery packs, in a project named DingoCharge. The wonderful write-up answers every question you have ...
Many people have phone and tablet chargers all over ... The rechargeable lithium-battery pack is housed in one of the earmuffs. The battery pack is 3.7 V and has a gray exterior.
The UniPal Plus is a universal battery charger which claims to be capable of charging "practically all" 3.6/3.7 or 7.2/7.4v Lithium-Ion batteries and can charge over 300 different camera batteries.