Power management system

A power management system comprising:

• a secondary battery pack;
• a battery measurement unit configured to measure a battery voltage VBAT of the secondary battery pack and a charge/discharge current IBAT, wherein, when the secondary battery pack is detected, the battery measurement unit measures a battery voltage VBAT1 in a state in which no load is connected to the secondary battery pack and a battery voltage VBAT0 and a load current IBAT0 in a state in which a dummy load is connected to the secondary battery pack;
• an initial resistance calculation unit configured to calculate an initial value ZBAT_init of the internal resistance of the secondary battery pack based on the Expression ZBAT_init=(VBAT1−VBAT0)/IBAT0 using the battery voltage VBAT and the charge/discharge current IBAT;
• and
• an aging evaluation unit configured to hold a reference value ZBAT_pre of the internal resistance acquired beforehand for the secondary battery pack before it ages, and to estimate an aging degree of the secondary battery pack based on a relation between the initial value ZBAT_init and the reference value ZBAT_pre.

A method for managing a secondary battery pack wherein a model of the secondary battery pack is made assuming that its internal resistance RINT is represented by the sum of a fixed component RF and a variable component RV,

• and wherein a correspondence relation between a state of charge SOC which indicates a relative remaining capacity with respect to a full-charge state of the secondary battery pack and an open circuit voltage OCV of the secondary battery pack is acquired beforehand,
• and wherein the method comprises:
• measuring a charge/discharge current IBAT and a battery voltage VBAT;
• calculating the internal resistance RINT;
• calculating a voltage drop VDROP by multiplying the internal resistance RINT by the charge/discharge current IBAT;
• estimating the open circuit voltage OCV of the secondary battery pack by adding the voltage drop VDROP to the present battery voltage VBAT;
• and
• acquiring the present state of charge SOC_ocv that corresponds to the present open circuit voltage OCV, based on the aforementioned correspondence relation.

A power management system comprising:

• a battery measurement unit configured to measure a battery voltage VBAT of a secondary battery pack, a charge/discharge current IBAT, and a temperature T;
• and
• a remaining capacity detection unit configured to calculate the remaining capacity of the secondary battery pack based on the battery voltage VBAT, the charge/discharge current IBAT, and the temperature T,
• wherein an internal resistance RINT of the secondary battery pack is modeled assuming that the internal resistance RINT is represented by the sum of a fixed component RF and a variable component RV,
• and wherein the remaining capacity detection unit comprises:
• an internal resistance calculation unit configured to calculate the internal resistance RINT;
• a voltage drop calculation unit configured to calculate a voltage drop VDROP by multiplying the internal resistance RINT by the charge/discharge current IBAT;
• an open circuit voltage calculation unit configured to calculate an open circuit voltage OCV of the second battery pack by adding the present battery voltage VBAT to the voltage drop VDROP;
• and
• a first charge state estimation unit configured to acquire a present state of charge SOC_ocv that corresponds to the present open circuit voltage OCV based on a correspondence relation between a state of charge SOC which indicates a relative remaining capacity of the second battery pack with respect to a full-charge state of the secondary battery pack and the open circuit voltage OCV of the secondary battery pack.