Power Systems & Reliability · SOP

Facility UPS Uninterruptible Power Supply Battery Health Audit

Standard procedure for in-depth health verification, impedance testing, and thermal imaging of stationary VRLA/Lead-Acid battery banks in 3-phase UPS systems to ensure runtime reliability and prevent thermal runaway.

Estimated Time
45 min per string
Difficulty
Advanced
Regulation
NFPA 70E / CSA Z462
Version
2.1
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Purpose

Establish baseline battery string impedance values, identify weak or marginal cells before they fail under load, and ensure upstream protective device coordination remains valid as internal resistance rises. A systematic failure to trend impedance data is the leading cause of preventable UPS runtime loss during mains disturbances.

Scope

Applies to all stationary Valve-Regulated Lead-Acid (VRLA) and Flooded Lead-Acid (VLA) battery strings supporting critical process UPS systems rated above 50 kVA. This audit covers open-rack and enclosed cabinet configurations commonly found in heavy industrial manufacturing and data centre environments.

Safety Precautions
  • LOTOVerify UPS static bypass is engaged and battery breaker is locked in open position. Verify absence of DC voltage with calibrated voltmeter before proceeding.
  • ARCCategory 2 arc flash suit, insulating rubber gloves (Class 00 minimum), safety glasses with side shields, and steel-toed boots. No exceptions.
  • TOOLInsulated tools only. Verify torque wrench calibration against certificate prior to use.
  • H₂Ensure ventilation is active and hydrogen gas monitor is functional before opening battery cabinet or cover.
Required Tools & Materials
  • Fluke 500 Series Battery Analyzer (or equivalent BITE3/PITE)
  • Infrared Thermal Imaging Camera (≥160x120 resolution, ±2°C accuracy)
  • Digital Multimeter, CAT III / 1000V rated, with calibrated leads
  • Insulated Torque Wrench (10–50 N·m range, with current calibration certificate)
  • Personal Protective Equipment (Arc Flash Cat 2, Rubber Gloves Class 00)
  • SOP Log Sheet or ServiceGrid Mobile App for data capture

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Procedure: Step-by-Step
1 Pre-Job Brief & LOTO. Perform shift turnover. Review one-line diagram and battery manufacturer O&M manual. Confirm static bypass is stable. Lock out battery breaker and tag. Verify zero DC voltage at breaker terminals with calibrated DMM.
2 Visual & Thermographic Scan. Open cabinet doors. Allow 5 minutes for thermal stabilization. Scan all intercell connections, terminals, and jar sides. Flag any component exhibiting temperature >+5°C above ambient string temperature for immediate investigation.
3 Float Voltage Measurement. Using your calibrated DMM, measure total string voltage at the battery breaker terminals. Record exact value. Compare to manufacturer’s recommended float voltage range.
4 Cell-Level Voltage & Impedance. Using the BITE3 analyzer, test each cell in sequence. Record voltage (Vdc) and internal resistance (mΩ). Calculate percentage deviation from the string average. Immediately flag cells beyond ±5% voltage variance.
5 Intercell Connection Resistance. Measure resistance across each intercell connector using the micro-ohmmeter function. Compare to baseline installation values. Flag any connection exceeding 20% above baseline for re-torque.
6 Data Analysis & Pass/Fail Criteria. Apply IEEE 1188 criteria: cells exceeding 25% impedance deviation from the string average are deemed marginal; cells exceeding 50% deviation are failed and must be flagged for scheduled replacement.
7 Reconnection & Restoration. Close battery breaker. Verify UPS rectifier accepts the DC bus without alarm. Remove LOTO tags and locks from breaker. Reset static bypass to normal operation. Confirm system status on UPS front panel.

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