Doohan iTango User Manual page 30

20%-80% if possible for cycle use.
⑥Do not store the battery in the environment if temperature is higher
than 40 degrees Celsius, otherwise it will cause irreversible capacity
fading of the battery.
⑦At low temperatures, the capacity of lithium batteries will capacity
fading in varying degrees: the available capacity for reference: -10 ℃ is
70%, 0℃ is 85%, and 25 ℃ is 100%.
⑧The most suitable storage capacity of the battery is 50%., long-term
storage will lead to irreversible capacity fading of the battery if less than
10% or higher than 90% of the power,If long-term storage of batteries,
please keep the battery at -10 ℃~ to 30℃, and to minimize capacity