The objective of the project was to create a case for a single cell Li-ion battery with built-in charger. Charging will be via the USB port, while the case will include a flying lead for connecting to MCU modules that can run at 3.3v via a regulator.
Alternate versions with a 5v buck converter or a 3.3v regulator included would be extremely useful.
Required components are are the charging module and a battery holder, together with whatever is needed for the flying lead. The case was designed to be a tight fit for the battery holder, with a separate compartment for the charger module and a cutout at the end for the USB port. The charger module is not designed to power the load, so the user is required to remove the load before applying power through the USB port.
The flying lead ends in a two-pin female socket that can be connected to a solderless breadboard or directly to the module using Dupont leads. A small inductor core with the lead looped through it serves as the strain relief, while a rubber plug is used to to provide a clean border for the hole in the case.
A short length of clear plastic rod, rounded at the top and lightly polished at both ends, is inserted into a raised section in the lid of the case so that the light from the charger LED is visible. The plastic piece is actually a section of sprue from a plastic model kit.
The lid is a simple press fit on the base. Two holes were molded into the bottom of the base so that the battery can be pushed out of the holder if required. The base also includes a locating peg for the holder.
This site was last updated 27th January 2022.