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Battery and UPS Systems Testing Flashcards

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Read the first 7 Battery and UPS Systems Testing flashcards as text

  1. When performing an AC ripple current test on a VRLA battery, what does excessive ripple current primarily indicate?

    Answer: Overcharging from the charger or inverter

    Excessive AC ripple current on VRLA batteries indicates a malfunctioning charger or inverter is imposing harmful alternating current that accelerates plate corrosion and shortens battery life.

  2. According to NETA MTS, what is the recommended maximum acceptable internal ohmic resistance increase for a lead-acid battery cell compared to its baseline before the cell is considered failed?

    Answer: 50% above baseline

    NETA MTS guidelines indicate a cell with internal ohmic resistance exceeding 50% above its established baseline should be flagged for replacement consideration.

  3. A UPS system is tested under a step-load change from 0% to 100% rated load. The output voltage dips by 12% and recovers within 20 ms. This result should be evaluated against which performance specification?

    Answer: IEC 62040-3 UPS performance classification

    IEC 62040-3 classifies UPS performance by output voltage deviation and recovery time under load transients, making it the applicable standard for this test.

  4. During a thermal imaging inspection of a battery string, one cell shows a surface temperature 15°C above adjacent cells. What is the most likely cause?

    Answer: Cell has elevated internal resistance causing excess heat

    A cell with elevated internal resistance dissipates more power as heat (P = I²R) during charge and discharge cycles, causing it to run hotter than neighboring cells.

  5. What is the primary purpose of equalizing charge on a vented lead-acid battery string?

    Answer: To bring all cells to a uniform state of charge and reverse sulfation

    Equalization applies a controlled elevated voltage to bring lagging cells up to full charge and dissolve minor sulfation, equalizing the state of charge across the entire string.

  6. When sizing a battery string for a UPS, the term 'end voltage' refers to what?

    Answer: The minimum cell voltage allowed before the battery is considered discharged

    End voltage is the minimum per-cell voltage threshold established by the manufacturer below which the battery should not be discharged to prevent irreversible damage.

  7. A stationary battery capacity test is stopped early when one cell reaches its end voltage while the string voltage is still above the minimum. What action should be taken?

    Answer: Stop the test and record the elapsed time and capacity delivered as the actual capacity

    Per IEEE 450/1188, a capacity test must be terminated when any cell reaches its end voltage, and the capacity delivered up to that point represents the true available capacity of the string.