Apple recommends to replace the battery at an authorized center when it reaches around 80% of its useful life. This replacement takes place generally within the first year and 9 months from the purchase of the device.
During night, when left charging, the device keeps the battery at his end-of-charge tension long after it has reached 100% in order to preserve it fully charged until the morning. This condition produces an excessive stress in the lithium-ion cells of the battery.
Thanks to ASO (Automatic Shut Off) Witty is able to recognize energy required by the device and disconnect it from the power when its energy need has been fulfilled.
By using Witty you can double the lifespan of a battery to almost 4 years from its purchase.