PowerBank
This is a custom USB PowerBank, running off an old Macbook battery in 3S2P for nominal 12v. this runs a 4-way USB socket and has inputs for a solar panel.
After rescuing an old Macbook, the only useful part worth salvaging was the battery. I bought an aluminium project box and a 12v to 4-port USB converter, which was mounted to the front panel. A pair of 4mm "Banana" style jacks were originally wired across the battery, giving a 12v output, and access for charging. These have since been re-purposed as the input for a small 20 watt solar panel.
The USB ports are fuse protected, and switched to prevent them draining the batteries when not in use. The cells each have a protection circuit to prevent over and under charging. The solar panel connects directly to a MPPT charge controller, which is connected directly to the battery. A bar chart style battery monitor has been fitted to the back. It has a push button for measuring the voltage. A day of good sunshine can easily fill the batteries 75%. When not out camping, it spends its time with the solar panel in a window, keeping the battery topped up.
