Maximum and minimum power limit calculator for parallel battery subpacks

1 . A battery system comprising:

M battery subpacks that are connected in parallel and that include battery control modules that calculate power values for said battery subpacks;

a control module that receives said power values from said M battery subpacks and that calculates a power value for said battery system based on a power level of one of said battery subpacks times a first factor, wherein said first factor is equal to a sum of one plus ratios of power values of others of said M battery subpacks divided by said power value of said one of said battery subpacks.

2 . The battery system of claim 1 wherein said power values from said battery subpacks are maximum power values.

3 . The battery system of claim 1 wherein said power values from said battery subpacks are minimum power values.

4 . The battery system of claim 1 wherein said battery control modules include:

a voltage module that measures a voltage V across at least one battery during first and second periods;

a current sensor that measures current I supplied by the at least one battery during said first and second periods; and

a limit module that estimates a sum of a polarization voltage V P and an open circuit voltage V φ of the at least one battery at said second period based on said voltage V and current I of the at least one battery at said first period and an ohmic resistance R 0 of the at least one battery.

5 . The system of claim 4 wherein said limit module calculates at least one of a maximum current limit I max and/or a minimum current limit I min for the at least one battery at said second period based on said sum, at least one of a maximum voltage limit V max and/or a minimum voltage limit V min , respectively, and said ohmic resistance R 0 of the at least one battery.

6 . The system of claim 4 wherein said first period occurs before said second period.

7 . The system of claim 5 wherein said limit module calculates at least one of a maximum power limit and a minimum power limit of the at least one battery based on said at least one of said maximum current limit I max and/or said minimum current I min limit, respectively, and said at least one of said maximum voltage limit V max and/or said minimum voltage limit V min , respectively.

8 . The battery system of claim 4 wherein said battery subpacks include N batteries that are connected in series with said at least one battery.

9 . The battery system of claim 1 wherein said battery control module includes:

a voltage module that measures voltage V across at least one battery at first and second periods;

a current sensor that measures current I supplied by the at least one battery at said first and second periods; and

a limit module that estimates a sum of a polarization voltage V P and an open circuit voltage V φ of the at least one battery at said second period based on said voltage V and current I of the at least one battery at said first period and an ohmic resistance R 0 of the at least one battery.

10 . The system of claim 9 wherein said limit module calculates at least one of a maximum voltage limit V max and/or a minimum voltage limit V min for the at least one battery at said second period based on said sum, at least one of a maximum current limit I max and/or a minimum current I min limit, respectively, and an ohmic resistance R 0 of the at least one battery.

11 . The system of claim 9 wherein said first period occurs before said second period.

12 . The system of claim 10 wherein said limit module calculates at least one of a maximum power limit and a minimum power limit of the at least one battery based on said at least one of said maximum current limit I max and/or said minimum current I min limit, respectively, and said at least one of said maximum voltage limit V max and/or said minimum voltage limit V min , respectively.

13 . The battery system of claim 9 wherein said battery subpack includes N-1 batteries connected in series with said at least one battery.