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

Presentation Topics Myths Misunderstandings that Lead to Mistakes 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

Myths

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

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

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

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

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

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

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 commissioning procedure only

Misunderstandings

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

Misunderstanding #1 (continued) Oops! Should be 101.5

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

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

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

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

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

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

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

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

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