This is the BMK low-amperage 1S Lipo DIS-charger:  text from BMK

This storage discharger is specifically designed for use with Micro JST 1.25mm batteries. Users can easily configure it for a discharge current of 50mA or 100mA. By default, it operates at a maximum output of 100mA and is suitable for all 1S LiPo batteries with a capacity of 50mAh or higher.

Using the Discharger

• Connect the battery.
• If the battery is fully charged, automatic discharging may occur.
• If not, simply click the button to start the process.
• The red LED will automatically turn off when the battery reaches a storage voltage of 3.8v.

Note: No need to watch while discharging. It will completely shut off on its own and you can safely leave it connected.