#Several Li-Ion Power Supply Options A collection of Li-Ion power supply designs for embedded use.
##Protected vs non-protected Cells Li-Ion cells come in protected and non-protected variants. In general, protection is achieved by an additional circuit that is integrated into the battery cell. Most 18650 cells come as "Protected" so the core cell will be disconnected when the cell voltage falls below a certain threshold level (typically 2V5 to 3V0).
##Non-protected Cell Circuit It's based on an extended TP4056 application (datasheet) that is sold at many places. In addition to the TP4056, it includes a DW01-G (datasheet) protection circuit and a 8205A MOSFET (datasheet). This article on Instructables discusses the board in very detail: ESP8266 - Li-Ion Battery rechargeable battery power solution
###Protected Cell Circuit A simpler board is this one - plain TP4056 application note implementation. It's discussed here in detail: Charger module with TP4056 controller
###Charge Current Selection Both boards have in common that the charge current is set to 1 A by an SMD resistor. Current can be reduced by increasing the resistor according to the TP4056 Datasheet.
##Voltage Regulation Both boards provide the raw battery voltage that can be in the range of 4V2 downto 3V0. Output voltage has to be regulated to the desired level. Several LDO regulators are availble for 3V3, this article chooses the PAM3101 . It comes in SOT23-5 package and can be deployed on a generic breakout board (eg Anvilex SOT23-6).