Method for determining amount of water to be added to a NiCd cell

• US 6,258,479 B1
• Filed: 08/20/1999
• Issued: 07/10/2001
• Est. Priority Date: 08/20/1999
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Rudai, Patrick M., Palanisamy, Thirumalai G., Hoenig, Steven, Singh, Harmohan
• Primary Examiner(s): Chaney, Carol
• Assistant Examiner(s): Martin, Angela J.
• Application Number:
  US09/378,256
• Time in Patent Office: 690 Days
• Field of Search: 429/90, 429/91, 429/92, 429/93, 429/61, 429/63, 429/50, 429/51, 429/49, 320/116, 320/118, 320/119, 320/120, 320/121, 320/122
• US Class Current: 429/61
• CPC Class Codes: H01M 10/484 for measuring electrolyte level, electrolyte density or electrolyte conductivity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Deficiencies in the electrolyte level of the cells of NiCd battery can be detected by measuring the internal resistance of the cells. Initially, data is collected for a battery type and capacity, correlating measured internal resistance with the amount of water that must be added to bring the cell resistance to an acceptable value. Subsequently, cells of other batteries of the same type and capacity can be measured to determine how much water must be added and the levels quickly restored. The polarization value of the cells can be used lieu of the internal resistance in the same fashion.

Claims

1. A method for determining the amount of water to be added to individual cells of a NiCd storage battery of a given rated capacity, said method comprising the steps of:

measuring(the internal resistance or determining the polarization value sequentially of each of the individual cells of the NiCd battery;

comparing the internal resistance or polarization value for each cell of the NiCd battery against a prior determined table correlating said values and amount of water to be added for a NiCd battery of said given capacity; and

adding to each cell individually the amount of water as determined from said prior determined table.

2. The method for determining the amount of water to be added to individual cells of a NiCd battery in accordance with claim 1 wherein the step of measuring the internal resistance of each cell comprises the steps of:

passing a step charge, a pulse, or a discharge pulse of current through each cell, the charge current and pulse width being the same as utilized for the creation of said prior predetermined table; and

measuring the resultant differential change in voltage across each cell.

3. The method for determining the amount of water to be added to individual cells of a NiCd battery in accordance with claim 1 wherein the steps of measuring the polarization value of each cell comprises the steps of:

passing constant current through the cell, said constant current being of the same value as utilized for the creation of said prior predetermined table; and

measuring the resultant change in voltage across each cell.

4. The method for determining the amount of water to be added to individual cells of a NiCd battery in accordance with claim 2 wherein the step of measuring the internal resistance or polarization of the individual cells includes the step of positioning onto the battery a battery terminal contact fixture having individual spring loaded contacts which physically engage the battery terminals of each of said cells.