10$ power bank / battery charger combo that you can use for day to day stuff but also outdoors.
- usb in - usb out (was that so hard?)
- It supports low power solar charging
- light (30g)
- they can be chained in series and will charge simultaneously if they get enough power, or one by one if they don't
- each charger is obviously self contained so no single point of failure
- on the negative side, it supports 3v rechargeable batteries only