Review on ⚡ Efficient E-flite 1S USB Li-Po Charger: Rapid 300mA Charging by Jon Bishop

Charger works well but not safe for less than 300mah battery without modification. One of the resistors needs to be replaced for safe use with smaller batteries. Adafruit makes a similar product for something safe up to 100mAh. Being a 300mAh charger, it will charge 150mAh batteries at 2°C and 70mAh at a whopping 4.3°C. The C rating on the battery refers to discharging, not that Load. The maximum safe discharge rate is determined by multiplying the specified C rating by the battery capacity.