NETA Battery and UPS Systems Testing 4

Question 1

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

Accepted Answer

Overcharging from the charger or inverter

Answer

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.

Question 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?

Accepted Answer

50% above baseline

Answer

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

Question 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?

Accepted Answer

IEC 62040-3 UPS performance classification

Answer

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

Question 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?

Accepted Answer

Cell has elevated internal resistance causing excess heat

Answer

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.

Question 5

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

Accepted Answer

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

Answer

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.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Battery and UPS Systems Testing 4