Method and apparatus for monitoring the operational state and stand-by of a battery

• US 5,218,288 A
• Filed: 01/29/1991
• Issued: 06/08/1993
• Est. Priority Date: 03/26/1990
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Mickal, Hermann, Fischer, Dietmar
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US07/647,470
• Time in Patent Office: 861 Days
• Field of Search: 320/13, 320/43, 320/44, 320/48, 307/66
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

A method and apparatus for monitoring the operational state (C_R) and stand-by (t_St) of a battery averages battery currents (I_B) and battery voltages (U_B) and determines the operating mode (charging L_A, or discharging, E_n) from the direction of the battery current (I_B). When discharging (E_n), a discharge power (P_En) is calculated form the average battery current (I_Bm) and battery voltage (U_Bm). The average cell voltage (U_BZ) is determined by dividing the average battery voltage (U_B) by the number of cells (Z_Z) in the battery. The cell discharge power (P_EnZ) is determined by dividing the discharge power (P_En) by the number of cells (Z_z) in the battery. Consequently, the cell discharge time (t_p) is known since it is proportional to the cell discharge power (P_EnZ). The cell discharge power (P_EnZ) is then compared with stored families of curves of cell voltage versus withdrawn capacity (C_En) and cell discharge power (P_EnZ). The withdrawn capacity (C_En) is determined from the average cell voltage (U_BZ) and the previously determined cell discharge power (P_EnZ). The withdrawn capacity (C_En) is subtracted from the maximum capacity (C_max) to determine the residual capacity (C_R), which is multiplied by the discharge time (t_p). Consequently with the aid of only one family of curves and without large expenses, the operational state (C_R) and the stand-by (t_St) of a battery can be monitored.

Claims

1. A method for monitoring an operational state (C_R) and a stand-by (t_St) of a battery comprising the steps of:

a) sensing a plurality of actual values of battery current (I_B);

b) sensing a plurality of actual values of battery voltage (U_B);

c) averaging the plurality of actual values of battery current (I_B) to determine an average battery current (I_Bm);

d) averaging the plurality of actual values of battery voltage (U_B) to determine an average battery voltage (U_Bm);

e) determining whether the battery is in a charge or a discharge mode (L_A, E_n) from a direction of the battery current (I_B);

f) calculating a discharge power (P_En), if the battery is in a discharge mode (E_n), from the average battery current (I_Bm) and the average battery voltage (U_Bm);

g) calculating an average cell voltage (U_BZ) from the average battery voltage (U_Bm) and the number of cells (Z_Z) in the battery;

h) calculating a cell discharge power (P_EnZ) by dividing the discharge power (P_En) by the number of cells (Z_Z) in the battery;

i) comparing the cell discharge power (P_EnZ) and the average cell voltage (U_BZ) with a plurality of families of curves of the average cell voltage (U_BZ) versus a withdrawn capacity (C_En) as a function of the cell discharge power (P_EnZ), to determine the withdrawn capacity (C_En);

j) subtracting the withdrawn capacity (C_En) from a maximum capacity (C_max) to determine the residual capacity (C_R); and

k) multiplying the residual capacity (C_R) by a discharge time (t_P), which is proportional to the calculated discharge power (P_EnZ), to get the stand-by (t_St) of the battery.

2. A method for monitoring an operational state (C_R) and a stand-by (t_St) of a battery, and for determining whether the battery is damaged, comprising the steps of:

a) bringing the battery into a discharge mode at a first time (T1);

b) sensing a plurality of actual values of battery current (I_B);

c) sensing a plurality of actual values of battery voltage (U_B);

d) averaging the plurality of actual values of battery current (I_B) to determine an average battery current (I_Bm);

e) averaging the plurality of actual values of battery voltage (U_B) to determine an average battery voltage (U_Bm);

f) calculating a discharge power (P_En) from the average battery current (I_Bm) and the average battery voltage (U_Bm);

g) calculating an average cell voltage (U_BZ) from the average battery voltage (U_Bm) and a number of cells (Z_Z) in the battery;

h) calculating a cell discharge power (P_EnZ) by dividing the discharge power (P_En) by the number of cells (Z_Z) in the battery;

i) comparing the cell discharge power (P_EnZ) and the average cell voltage (U_BZ) with a plurality of families of curves of the average cell voltage (U_BZ) versus a withdrawn capacity (C_En) as a function of the cell discharge power (P_EnZ), to determine the withdrawn capacity (C_En);

j) subtracting the withdrawn capacity (C_En) from a maximum capacity (C_max) to determine the residual capacity (C_R);

k) multiplying said residual capacity (C_R) by a discharge time (t_P), which is proportional to the discharge power (P_EnZ), to get a first stand-by (t_St1) of the battery;

l) bringing the battery into the discharge mode at a second time (T2) and repeating steps b) through j) to determine the residual capacity (C_R) at the second time (T2) wherein the second time (T2) is separated in time from said first time (T1) by a predetermined length of time (t_A);

m) multiplying said residual capacity (C_R) at the second time by the discharge time (t_P) to get a second stand-by (t_St2) of the battery;

n) subtracting the second stand-by (t_St2) from the first stand-by (t_St1) to obtain a difference value (t_diff); and

o) comparing the difference value (t_diff) with said predetermined length of time (t_A), whereby if the difference value (t_diff) is outside of a predetermined tolerance band of the length of time (t_A), the battery is detected to be damaged.

3. An uninterruptible power system comprising:

a) a battery having an input and an output;

b) a rectifier having an output coupled to the output of the battery and converting ac voltage to dc voltage;

c) an inverter having an input coupled to the output of the battery, having an output, and converting dc voltage to ac voltage;

d) a power supply switch-back device having an input coupled to the output of the inverter; and

e) a controlling system coupled to the input and the output of the battery;

f) a circuit monitoring an operational state (C_R) and a stand-by (t_St) of the battery integrated into said controlling system.

4. An apparatus for monitoring an operation state (C_R) and a stand-by (t_St) of a battery comprising:

a) means for sensing voltage from said battery;

b) means for sensing current from said battery;

c) a microprocessor, said microprocessor being electrically connected to said means for sensing voltage from said battery and said means for sensing current from said battery;

d)a memory providing input to said microprocessor;

said microprocessor receiving a plurality of battery voltages and a plurality of battery currents, and calculating the operational state (C_R) and the stand-by (t_St) from the plurality of battery voltages and currents and the input from the memory; and

e) a display displaying the operational state (C_R) and the stand-by (t_St) of the battery,

wherein said memory contains a family of curves of a cell voltage (U_BZ) versus a withdrawn capacity (C_En) at a constant discharge power to be output from said memory and input to said microprocessor.

5. An apparatus for monitoring an operation state (C_R) and a stand-by (t_St) of a battery comprising:

a) means for sensing voltage from said battery;

b) means for sensing current from said battery;

c) a microprocessor, said microprocessor being electrically connected to said means for sensing voltage from said battery and said means for sensing current from said battery;

d) a memory providing input to said microprocessor;

said microprocessor receiving a plurality of battery voltages and a plurality of battery currents, and calculating the operational state (C_R) and the stand-by (t_St) from the plurality of battery voltages and currents and the input from the memory; and

e) a display displaying the operational state (C_R) and the stand-by (t_St) of the battery,

wherein said memory contains a family of curves relating a cell voltage (U_BZ) to a withdrawn capacity (C_En) and time to be output from said memory and input to said microprocessor.

6. An apparatus for monitoring an operational state (C_R) and a stand-by (t_St) of a battery comprising:

a) means for sensing voltage from said battery;

b) means for sensing current from said battery;

c) a microprocessor, said microprocessor being electrically connected to said means for sensing voltage form said battery and said means for sensing current from said battery;

d) a memory providing input to said microprocessor;

said microprocessor receiving a plurality of battery voltages and a plurality of battery currents, and calculating the operational state (C_R) and the stand-by (t_St) from the plurality of battery voltages and currents and the input from the memory; and

c) a display displaying the operational state (C_R) and the stand-by (t_St) of the battery,

wherein said memory contains a family of curves of a cell voltage (U_BZ) versus a withdrawn capacity (C_En) at a constant discharge power and time to be output from said memory and input to said microprocessor.