>>1933466>>1934241Also, if you’re interested in the stuff, get yourself a cheap multimeter and soldering iron and start fucking around. Just make sure you respect the electrons because lithium batteries can pack quite a lot of power into a little thing, you will get sparks and smoke very quickly if you cross a wire.
If you ever see these $5 power banks about the size of a lipstick tube, they’re just a lithium cell (often 18650) and a protection board with USB in/out. The USB in takes 5V from the charging cable, converts that to the proper voltage and current to charge the 3.7v lithium cell, and then the USB Out steps that 3.7V back up to 5V (the voltage all the USB chargers use) and limits the current to protect the cell as well as cutting off the power when the cell voltage gets too low.
