Charging Lithium Ion batteries is complicated. You can buy simple charge circuits that will charge one cell (or cells in parallel) at up to 1A and stop when it is full. They are based on the TP4056 chip. They usually also have a DW01 protection chip on to turn the output off if the battery gets too low.2 * 3.7 volts is 7.4 volts. Feed into a regulator to get 5 volts. The combined charging voltage would be 8.8 but the batteries could be charged in parallel from USB 5 volts or in series from 12 volt.
Charging in series is harder. You have to monitor each cell and be able to balance the charge if one cell charges faster than the other There are balancing modules for that.
For a Zero or Zero 2W I sometimes use a UPS module with one 18650 and a 5V input and output. They charge the cell when power is on, and provide 5V all the time. You can get ready made units for a Pi that just need the battery.
Statistics: Posted by rpdom — Thu May 09, 2024 12:07 pm