Power storage device and power storage system

A power storage system comprising:

• a secondary battery;
• sensors;
• a micro controller unit;
• and
• a memory including a transistor,
• wherein the memory comprises a first memory region and a second memory region,
• wherein the secondary battery is configured to operate in a first operation mode and a second operation mode,
• wherein the sensors are configured to obtain information of the secondary battery,
• wherein the micro controller unit is configured to determine whether the secondary battery is in the first operation mode or the second operation mode in accordance with the information, and in the case where the secondary battery is in the first operation mode, the micro controller unit stores the information in the first memory region, and in the case where the secondary battery is in the second operation mode, the micro controller unit stores the information in the second memory region, and
• wherein the transistor comprises an oxide semiconductor film including a channel formation region,
• wherein the first operation mode is a charge mode including a constant-current charge mode and a constant-voltage charge mode,
• wherein the second operation mode is a discharge mode including a rapid discharge mode,
• wherein a remaining battery power, a voltage, a current, and a temperature at a start time of each the constant-current charge mode, the constant-voltage charge mode, and the rapid discharge mode and an ending time of the corresponding mode are stored in the first memory region,
• wherein a time period from the start to end of each the constant-current charge mode, the constant-voltage charge mode, and the rapid discharge mode is stored in the first memory region, and
• wherein maximum value of current flowing during the rapid discharge mode is stored in the second memory region.