RESTORING CAPACITY TO A VRLA AGM BATTERY by addition of Water and Catalysts

1. RESTORING CAPACITY TO A VRLA AGM BATTERY by addition of Water and Catalysts PES/SCC-29 meeting 9/30/01 Bloomingdale, IL Peter DeMar Battery Research and Testing, Inc.

2. Site Conditions • Microwave communications site. • Twelve cells. • Climate controlled at 65 to 80 degrees F. • Quality communication rectifiers. • On site automatic generator backup. • Infrequent loss of AC power to the site.

3. BATTERY INFORMATION • Mfg. GNB • Model 75A-23 • Rating 825 AH • Mfg Date March 1992 • Orientation Vertical

4. Inspection Checks • During each inspection we checked the following items. • Over-all voltage • Individual cell voltage • Individual cell impedance • Cell temperatures • Intercell connection resistance • Ambient temperature • Charge current

5. As found conditions7/14/00 • Average cell impedance 467 microhms. High 592 microhms. Low 386 microhms. • Charge current 3.6 amps. • Ambient temperature 72 degrees. • Average cell voltage of 2.266. High 2.29 volts. Low 2.26 volts. • Capacity as tested on 5/18/00 was 32% of the published 3 hour rating to 1.75 VPC.

6. Corrective actions Thirty ounces of water was added to each cell. • Cat-Vent assemblies were added to each cell. • All work was performed with the battery in service.

7. 7/14/00 follow up inspection • Two hours after the completion of the Rehydration process we again inspected the battery. • The average impedance had dropped from 467 microhms to 296 microhms. • There were still 3 cells that were substantially higher than the rest. Two of these had been the highest before the process.

8. 7/19/00 load test • Battery was reinspected. • Charge current had dropped from 3.6 amps to 2.2 amps in just 5 days. • The average impedance had dropped from 467 microhms to 274 microhms. There were still three cells that were higher than the rest by a significant amount. • We ran the load test at the three hour rate. The battery lasted 133 minutes. Which equates to 66%. This is a 206% increase from the as found capacity.

9. Actions following 7/19/00 load test • An additional 8 ounces of water was added to cells 7 and 8. • The string was placed back on float charge.

10. 6/10/01 load test • The battery was reinspected just prior to the load test. • Float current had dropped to .9 of an amp • Average impedance was 271 microhms • Load test was run at the three hour rate to 1.75 VPC. • Test was terminated at 166 minutes. This equates to 92%. Which was a 288% increase from the as found capacity.

11. Float Voltages

12. FLOAT CHARGE CURRENT

13. CELL IMPEDANCE

14. STRING CAPACITY

15. Summary • Average impedance dropped from 467 microhms to 271 microhms. These cells were 172% higher that they should have been. • Charge current dropped from 3.6 amps to .9 of an amp. These cells were requiring 400% more charge current than they should have. • String capacity increased from 32% to 92%.

16. Conclusion • The general condition of a VRLA AGM battery string can be determined from a thorough inspection, which includes charge current, and internal ohmic values, as long as the correct ohmic values have been calculated or are known as compared to a load test. • Individual cell float voltages are meaningless in predicting cell capability. • Adding water and Catalysts to VRLA AGM cells will restore capacity that is lost due to either dry out, or lack of compression, and will maintain that restored capacity.