Method for estimating state of health of a battery in a hybrid vehicle

1. A method for estimation of State-of-health (SOH) characteristics of a battery in hybrid vehicles, comprising:

charging and discharging the battery at least one time within an upper region of a State-of-charge (SOC) window, wherein the battery:

i) is charged to a first predetermined level in the upper region of the SOC window during a first time period;

ii) is charged by a first charge current impulse for pushing the SOC level of the battery to a level above the first predetermined level and outside the SOC window, during a second time period;

iii) is discharged by an electrical machine to a second predetermined level within the SOC window;

charging and discharging the battery at least one time within a lower region of the SOC window wherein the battery:

i) is charged to a third predetermined level in the SOC window, during a third time period;

ii) is discharged by an electrical machine to a fourth predetermined level in the SOC window;

iii) is discharged by a second current impulse, for pushing the SOC level of the battery to a level below the fourth predetermined level and below the SOC window, during a fourth time period;

calibrating a battery management unit comprised in the hybrid vehicle by using the reached levels outside the SOC window for determining correct upper and lower edges of the current soc window;

estimating the SOH characteristics of the battery during the charge and discharge periods by using the battery management unit for determining the condition of the battery in comparison to a new and unused battery by comparing the current SOC window with a standard SOC window,

wherein; the first and third time period is longer than the second and fourth time period respectively; and

the first predetermined level represents a higher voltage, than the second predetermined level and the third predetermined level represents a higher voltage, than the fourth predetermined level.

2. The method according to claim 1 , wherein the charge current impulse is created by means of a combustion engine of the vehicle powering the electrical machine in generative operation.

3. The method according to claim 1 , wherein the discharge currents impulse is created by the electric machine in a motoring operation driving a combustion engine of the vehicle.

4. The method according to claim 1 , further comprising the step of:

a. connecting the battery of the vehicle to a charge pole, wherein the charge current pulse and the discharge current pulse is created by means of the charge pole.

5. The method according to claim 3 , wherein the combustion engine acts as a brake by its friction.

6. The method according to claim 3 , wherein the combustion engine acts as an engine retarder.

7. The method according to claim 1 , wherein the method further comprises the step of:

a. calibrating the SOC window by using the estimated SOH characteristics.