Handy Test Battery and Charger
This provides a handy portable logic-level power source for bench top use during testing.
It is based on a 2AH 16500 Li-Ion battery and has these modules:
1. A charger with USB input and JST output connectors,
2. A DC-DC converter.
It has switches to provide these outputs:
1. 4.2V from the charger if the USB is connected.
2. Direct from the battery,
3. Fixed and variable voltage from the DC-DC converter,
The charger has a switch to select 3 charging currents in the constant-current region: 100, 200 and 500 MA. Its maximum output voltage is 4.2V.
The DC-DC converter has a recessed slide switch to select its output voltage: 3.3. 5. or variable 0.8 to 9V. The slide switch is so tiny and recessed it needs a tool such as a tweezer to operate.
A switch connects the battery. Another switch selects whether the output positive (red) terminal is connected to the battery or the DC-DC converter, It has a center-off position.