Method and device for calculating state of health of battery
A method for calculating state of health of battery, performed by a processing control circuit, includes: charging a battery under test to an upper voltage with a first constant current through a charging circuit and an electrical measuring circuit, discharging the battery under test to a lower voltage with a second constant current through the charging circuit and the electrical measuring circuit, obtaining an accumulated discharge capacity from the upper voltage to the lower voltage through the electrical measuring circuit, and calculating a state of health of the battery under test at least according to the accumulated discharge capacity and a design capacity.
1. A method for calculating state of health of battery, performed by a processing control circuit, comprising:
charging a battery under test to an upper voltage with a first constant current through a charging circuit and an electrical measuring circuit;
discharging the battery under test to a lower voltage with a second constant current through the charging circuit and the electrical measuring circuit;
obtaining an accumulated discharge capacity from the upper voltage to the lower voltage through the electrical measuring circuit; and
calculating a state of health of the battery under test at least according to the accumulated discharge capacity and a design capacity,
wherein calculating the state of health of the battery under test at least according to the accumulated discharge capacity and the design capacity comprises:
calculating a sum of the accumulated discharge capacity, an unused capacity and an aged capacity, and dividing the sum by the design capacity to obtain a quotient, wherein the unused capacity is a difference between a current state of charge and a full state of charge that is pre-stored by a memory connected to the processing control circuit, and the aged capacity is a difference between a current capacity and the design capacity; and
using the quotient as the state of health.
2. The method for calculating state of health of battery according to claim 1 , wherein the upper voltage and the lower voltage correspond to a common charge level range of the battery under test.
3. The method for calculating state of health of battery according to claim 1 , wherein before charging the battery under test to the upper voltage with the first constant current through the charging circuit and the electrical measuring circuit, the method further comprises:
charging a control battery with a constant voltage;
stopping said charging when charge level of the control battery reaching maximum charge level;
discharging the control battery with a third constant current;
obtaining a charge-voltage relationship from the maximum charge level to minimum charge level of the control battery when the charge level of the control battery reaching the minimum charge level;
obtaining an open circuit voltage characteristic according to the charge-voltage relationship;
setting the upper voltage according to the open circuit voltage characteristic and an upper limit of a common charge level range of the battery under test; and
setting the lower voltage according to the open circuit voltage characteristic and a lower limit of the common charge level range.
4. The method for calculating state of health of battery according to claim 1 , wherein calculating the state of health of the battery under test at least according to the accumulated discharge capacity and the design capacity further comprises:
obtaining the current state of charge corresponding to the upper voltage through the electrical measuring circuit.
5. The method for calculating state of health of battery according to claim 1 , wherein before charging the battery under test to the upper voltage with the first constant current through the charging circuit and the electrical measuring circuit, the method further comprises:
charging the battery under test to a default initial voltage.
6. A device for calculating state of health of battery, comprising:
a charging circuit;
an electrical measuring circuit;
a memory configured to store an upper voltage, a lower voltage, a design capacity and a full state of charge of a battery under test; and
a processing control circuit connected to the charging circuit, the electrical measuring circuit and the memory, and configured to perform:
charging the battery under test to the upper voltage with a first constant current through the charging circuit and the electrical measuring circuit;
discharging the battery under test to the lower voltage with a second constant current through the charging circuit and the electrical measuring circuit;
obtaining an accumulated discharge capacity from the upper voltage to the lower voltage through the electrical measuring circuit; and
calculating a state of health of the battery under test at least according to the accumulated discharge capacity and the design capacity,
wherein calculating the state of health of the battery under test at least according to the accumulated discharge capacity and the design capacity comprises:
calculating a sum of the accumulated discharge capacity, an unused capacity and an aged capacity, and dividing the sum by the design capacity to obtain a quotient, wherein the unused capacity is a difference between a current state of charge and the full state of charge, and the aged capacity is a difference between a current capacity and the design capacity; and
using the quotient as the state of health.
7. The device for calculating state of health of battery according to claim 6 , wherein the upper voltage and the lower voltage correspond to a common charge level range of the battery under test.
8. The device for calculating state of health of battery according to claim 6 , wherein the processing control circuit is further configured to perform:
controlling the charging circuit to charge a control battery with a constant voltage;
stopping said charging when charge level of the control battery reaching maximum charge level;
discharging the control battery with a third constant current;
obtaining a charge-voltage relationship from the maximum charge level to minimum charge level of the control battery when the charge level of the control battery reaching the minimum charge level;
obtaining an open circuit voltage characteristic according to the charge-voltage relationship;
setting the upper voltage according to the open circuit voltage characteristic and an upper limit of a common charge level range of the battery under test; and
setting the lower voltage according to the open circuit voltage characteristic and a lower limit of the common charge level range.
9. The device for calculating state of health of battery according to claim 6 , wherein the processing control circuit is further configured to obtain the current state of charge corresponding to the upper voltage through the electrical measuring circuit.
10. The device for calculating state of health of battery according to claim 6 , wherein the processing control circuit is further configured to control the charging circuit to charge the battery under test to a default initial voltage before charging the battery under test to the upper voltage with the first constant current through the charging circuit and the electrical measuring circuit.
11. The device for calculating state of health of battery according to claim 6 , wherein the electrical measuring circuit comprises a voltage sensor configured to detect the upper voltage and the lower voltage of the battery under test.
12. The device for calculating state of health of battery according to claim 6 , wherein the electrical measuring circuit comprises an analog coulombic integrator configured to detect the accumulated discharge capacity of the battery under test.