Dual zone discharge of rechargeable batteries

A device for charging a rechargeable battery, the device comprising:

• a set of electrical contacts configured to receive a connection to the battery;
• and
• a control circuit comprising one or more processing devices, the control circuit configured to:
• determine that an amount of charge remaining in the battery is more than a threshold percentage of a capacity of the battery, wherein the battery is characterized by a discharging profile that includes (i) an upper plateau corresponding to a substantially constant first voltage and (ii) a lower plateau corresponding to a substantially constant second voltage that is less than the first voltage, and wherein the threshold percentage of the capacity of the battery corresponds to a transition between the upper plateau and the lower plateau,
• responsive to determining that the amount of charge remaining in the battery is more than the threshold percentage of the capacity of the battery, discharge the battery while being connected to the device until at least the threshold percentage of the capacity of the battery is discharged, and
• initiate charging of the battery when the amount of charge remaining in the battery is less than the threshold percentage of the capacity of the battery.