Battery float management

• US 7,772,851 B2
• Filed: 07/02/2004
• Issued: 08/10/2010
• Est. Priority Date: 07/02/2003
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Power Quality Co (Eaton Corporation PLC.)
• Inventors: Hunter, Phillip, Al-Anbuky, Adnan
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): Berhanu; Samuel
• Application Number:
  US10/568,260
• Publication Number:
  US 20070080668A1
• Time in Patent Office: 2,230 Days
• Field of Search: 324/429, 324/430
• US Class Current: 324/430
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: H01M 10/121 Valve regulated lead acid batteries [VRLA]
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/4285 Testing apparatus
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention relates to a new VRLA battery float model. The model covers the steady state and transient float charge behavior of both positive and negative electrodes. Backup analysis verifies the internal polarization distribution for a conventional 2V-cell polarization behaviors can be identified without the need for a physical reference electrode. The estimated individual electrode polarization allows early detection of common failure modes like negative plate discharge as well as a reference for float voltage optimisation. Furthermore, the positive polarization relating to minimum grid corrosion may be correlated with the occurrence of the peak of a “Tafel” like resistance used by the model. The model encourages utilisation of low signal perturbation for testing a cell'"'"'s state of health and state of charge conditions while at float.

Claims

1. A method for determining polarization of an electrode of a VRLA battery, the method including the steps of:

allowing the battery to discharge for a selected period of time, monitoring the battery voltage during the selected period, detecting a first change in the battery voltage during the selected period of time and a second change in the battery voltage during the selected period of time, and associating the first change with polarization of a negative electrode and the second change with polarization of a positive electrode, and determining the polarization of the electrode from the associated change in the battery voltage during the selected period of time.

2. A method as claimed in claim 1 including detecting the magnitude of the change in voltage to determine the polarization of the electrode.

3. A method as claimed in claim 1 including comparing the polarization of at least one electrode with an expected polarization value or range of polarization values to determine parameters of a float charge to be applied to the battery.

4. A method as claimed in claim 1 wherein the step of discharging comprises open circuit charge leakage.

5. A method as claimed in claim 1 wherein the step of discharging comprises closed circuit enforced discharging.

6. A method as claimed in claim 1 wherein the step of discharging occurs as part of a current perturbation applied to the battery.

7. A method as claimed in claim 6 wherein the polarization of the negative electrode is determined.

8. A method as claimed in claim 1 further including the step of using the difference between the battery voltage prior to discharge and the polarization detected to determine the polarization of the other electrode.