System and method for monitoring a DC power system

• US 10,228,424 B2
• Filed: 07/03/2018
• Issued: 03/12/2019
• Est. Priority Date: 05/11/2015
• Status: Active Grant

• Current Assignee: Hindlepower, Inc.
• Original Assignee: Hindlepower, Inc.
• Inventors: Hindle, William A., Hindle, Nicholas C., Beck, Robert, Meisner, Larry S.
• Primary Examiner(s): Aurora, Reena
• Application Number:
  US16/026,566
• Publication Number:
  US 20180313903A1
• Time in Patent Office: 252 Days
• Field of Search: 324434
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: G01R 31/44 Testing lamps
• CPC Class Codes: H01M 10/4285 Testing apparatus
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00

Abstract

The present application discloses an integrated direct current (DC) subsystem monitoring system for monitoring and reporting status of a utility substation, the DC subsystem monitoring system having the ability to actively monitor and report on changes in the float current and current capacity of the system, as well as to monitor for ground faults.

Claims

1. A method for performing a capacity test on testing a battery bank comprising at least one battery, the battery bank being part of a load circuit in which the battery bank, a charger, and a system load are arranged in parallel, the battery bank having a nominal capacity and a set of capacity factors, the set of capacity factors including first and second capacity factors K_t1 and K_t2, the method comprising:

(a) electrically disconnecting the battery bank from the charger and the system load;

(b) placing the battery bank in electrical contact with a capacity test circuit operationally configured to apply a constant resistance across the battery bank;

(c) maintaining the battery bank in electrical contact with the capacity test circuit until the battery bank reaches a predetermined end voltage;

(d) measuring a time to end voltage TD₂ comprising a period from the start of step (b) to the end of step (c);

(e) measuring a temperature that is indicative of a temperature of the battery bank and calculating a temperature correction factor T_cf based on the measured temperature;

(f) calculating an average current I_avg consisting of the mean of a first set of measurements of a current flowing through the capacity test circuit, each of the measurements of the first set of measurements being taken at first frequency during the performance of step (c);

(g) calculating an average capacity factor K_t that is equal to the nominal capacity divided by the average current I_avg;

(h) calculating a rated discharge time t for the capacity test performed in steps (a) through (d) as a function comprising a linear interpolation between first and second capacity factors K_t1 and K_t2; and

(i) calculating a percentage C of the nominal capacity as a function of the rated discharge time t, the measured time to end of-voltage TD₂, and the temperature correction factor T_cf.

2. The method of claim 1, wherein step (h) further comprises calculating a rated discharge time t for the capacity test performed in steps (a) through (d) based on the following formula:

3. The method of claim 1, wherein step (i) comprises:

(j) calculating a percentage C of the nominal capacity based on the following formula;

4. The method of claim 1, wherein the battery bank includes a plurality of battery cells, and the measured temperature of step (e) comprises an average temperature of at most 10% of the plurality of battery cells.

5. The method of claim 4, wherein the measured temperature of step (e) consists of a temperature of only one of the plurality of battery cells.

6. The method of claim 1, further comprising:

(k) measuring an inter-cell connection resistance of the battery bank and determining whether the inter-cell connection resistance is within a predetermined range;

wherein step (k) is performed prior to step (a).

7. The method of claim 1, further comprising:

(1) measuring an electrolyte level of the battery bank and determining whether the electrolyte level is at a predetermined value;

wherein step (1) is performed prior to step (a).

8. The method of claim 1, further comprising:

(m) verifying whether one or more DC system failure back-up precautions are active;

wherein step (m) is performed prior to step (a).

9. The method of claim 1, further comprising:

(n) electrically disconnecting the capacity test circuit from the battery bank, and reconnecting the battery bank to the charger and the system load;

wherein step (n) is performed after step (c).

10. The method of claim 1, wherein the first frequency is at least 0.0167 Hz.

11. The method of claim 1, wherein the first frequency is at least 0.1 Hz.

12. A method for performing a capacity test on a battery bank comprising at least one battery, the battery bank having a nominal capacity, the method comprising:

(a) connecting the battery bank to a capacity test circuit, the capacity test circuit being configured to apply a constant resistance across the battery bank;

(b) measuring a current flow through the capacity test circuit at predetermined intervals from the start of step (a) to when the battery bank reaches a predetermined end voltage, yielding a plurality of current flow measurements;

(c) calculating an average current I_avg consisting of a mean of the plurality of current flow measurements;

(d) calculating an average capacity factor K_t that is equal to the nominal capacity divided by the average current I_avg; and

(e) calculating a percentage C of the nominal capacity based on the average capacity factor K_t.

13. The method of claim 12, wherein the battery bank includes a set of capacity factors including first and second capacity factors K_t1 and K_t2;

and the method further comprises;

(f) calculating a rated discharge time t for the capacity test performed in steps (a) through (b) as a function comprising a linear interpolation between first and second capacity factors K_t1 and K_t2.

14. The method of claim 13, wherein step (f) includes calculating a rated discharge time t for the capacity test performed in steps (a) through (b) based on the following formula:

15. The method of claim 13, further comprising:

(g) measuring a time to end voltage TD₂ comprising a period from the start of step (a) to the end of step (b);

wherein step (e) includes calculating the percentage C of the nominal capacity as a function of the rated discharge time t and the measured time to end voltage TD₂.

16. The method of claim 15, further comprising:

(h) measuring a temperature that is indicative of a temperature of the battery bank and calculating a temperature correction factor T_cf based on the measured temperature;

wherein step (e) includes calculating a percentage C of the nominal capacity as a function of the rated discharge time t, the measured time to end voltage TD₂, and the temperature correction factor T_cf.

17. The method of claim 12, wherein each of the predetermined intervals is equal to a single measurement interval, the measurement interval being less than one minute.

18. The method of claim 17, wherein the measurement interval is less than ten seconds.