Performance Testing Lead-Acid Stationary Batteries; Myths, Misunderstandings and Mistakes

1. Performance Testing Lead-Acid Stationary Batteries; Myths, Misunderstandings andMistakes Rick Tressler Sr. Training Engineer Alber IEEE PES Energy Storage & Stationary Battery Committee Sunday Technical Sessions June 12, 2016

2. Presentation Topics • Myths • Negative effects of performance testing • Equalizing a VLA battery before a test • Equalizing a VRLA battery prior to a performance test • Misunderstandings that Lead to Mistakes • Test termination at 100% capacity • Failure to bypass weak cells • Load bank cable sizing • Test termination at first cell final voltage • High rates on small connectors

3. Myths

4. Myth #1 • Performance testing ruins a battery • A lead calcium, flat plate, 1.215 S.G. battery can deliver about 50 cycles to 80% DOD when tested at the 5 hour rate to 1.75 VPC • IEEE based testing results in about 6 cycles to about 50% DOD • Test at 1 to 2 hour rate at the corresponding higher current instead

5. Myth #1 (continued) • Example test schedule • Test #1 Acceptance test at installation • Test #2 Performance test within 2 years of installation – weeds out early failures • Tests #3-5 Performance test at 5 year intervals (20 year expected service life) • Test #6 Begin testing annually until reaching 80% rated capacity

6. Myth #2 • Always equalize a VLA battery before a test • What kind of test? • It’s appropriate prior to Acceptance tests • Equalize charging when new is termed Initial, Commissioning or Freshening charge • No less than 3 days but not longer than 30 days on float prior to testing after completing charge

7. Myth #2 (continued) • Performance testing? • Do not equalize unless the intent is to baseline/benchmark capacity (Acceptance test) • Usually performed to reflect maintenance practices • Batteries do not get equalized before an emergency outage occurs

8. Myth #2 (continued) • The elusive “72 hour” equalize before a test rule • Where did it come from? • Probably the result of some urban battery legend • Equalize a battery for 72 hours, regardless of type, size, application, then run a test – NO! • There is no one-size-fits-all equalize procedure

9. Myth #2 (continued) • Table clearly indicates the equalize time varies widely

10. Myth #3 • Equalize VRLA batteries prior to a Performance test • This should not be conducted unless specifically indicated by the battery manufacturer • Generally part of the commissioningprocedure only

11. Misunderstandings

12. Misunderstanding #1 • Terminating a Performance Test When Battery Capacity Reaches 100% • Example 58 cell battery • Published time -1 hour rate • Published final voltage – 1.75 VPC • Battery final voltage should be 101.5 V

13. Misunderstanding #1 (continued) Oops! Should be 101.5

14. Misunderstanding #2 • Failure to bypass weak cells • Testing with a failed cell in the circuit prior to 90%-95% of expected time can skew test results • Before 90%, discontinue or pause the test, bypass the cell, then resume

15. Misunderstanding #2 (continued) • Cell failure occurs later than 90%-95%? • Continue the testing to the specified final battery voltage • Caveats • Bypassing cells is allowed once during a test • Maximum downtime to be not longer than 10% of test time or 6 minutes, whichever is shorter

16. Misunderstanding #3 • Failure to Correctly Size Load Bank Cables • Voltage drop must be considered when load banks are being operated near or at full load rating • May not be able to achieve required load current • Cable overheating also a concern

17. Misunderstanding #3 (continued) • Example • Cable Size (CM) = 12.9 × loop conductor × load ÷ max drop • 12.9 × 100 × 450 amperes ÷ 3.0 v • Cable size = 193,500 CM (4/0 cable, 211,600 CM) – 1 conductor per polarity recommended

18. Misunderstanding #4 • Terminating a Test When the First Cell Reaches Final Voltage • Such action renders the test invalid • Test termination criteria is the point in the test when overall battery voltage occurs, not when the first cell reaches the average end-of-discharge voltage

19. Misunderstanding #4 (continued) • Cell voltages vary during discharge • Perfect uniformity is not achievable • There is always cell voltage variation

20. Misunderstanding #5 • High Test Currents with Small Intercell Connectors • 8 hour battery tested at the 1 to 2 hour rate • Exercise caution; avoid excessive voltage drop and possible overheating of connectors • Consult battery manufacturer if in doubt • Do no harm to the battery

21. Summary • Testing requires a good understanding of batteries • Proper technician training is essential • An understanding of the applicable IEEE recommended practice should be more than casual • Maintain copies of current standards in your digital library • Documented procedures are extremely useful • Seek answers to questions before testing • Be prepared for the unexpected

22. Performance Testing Lead-Acid Stationary Batteries; Myths, Misunderstandings andMistakes Rick Tressler Sr. Training Engineer Alber IEEE PES Energy Storage & Stationary Battery Committee Sunday Technical Sessions June 12, 2016