The Mini-Battery-Supervisor is a tiny circuit which makes it possible use a battery pack as power supply for low-power USB electronic appliances, while keeping the ability to connect a USB cable when needed. 

More precisely, the Mini-Battery-Supervisor has four purposes:

It reduces the voltage provided by the battery to 5V, which is the maximal voltage expected by USB powered appliances;

It monitors the battery voltage to cleanly cut the appliance power supply when the battery is fully unloaded, in order to protect the appliance and the battery;

It makes it possible to connect simultaneously the battery and an external USB host to the appliance, for configuration and diagnosis purposes;

It features a rugged panel-mount USB Micro-B connector, that can be integrated in the front panel of an enclosure for instance.