EGSA Battery and Starting Systems 2 — Questions and Answers
Question 1: A battery charger for a standby generator is typically sized at what percentage of the battery's amp-hour (Ah) capacity?
- 1% to 3%
- 5% to 10% (Correct answer)
- 15% to 25%
- 30% to 50%
Correct answer: 5% to 10%
Battery chargers for standby applications are generally sized at 5% to 10% of the battery's Ah capacity to provide adequate float and recharge capability without overcharging.
Question 2: What hazardous gas is produced during the charging of flooded lead-acid batteries that requires adequate ventilation?
- Carbon dioxide
- Nitrogen oxide
- Hydrogen (Correct answer)
- Sulfur dioxide
Correct answer: Hydrogen
Flooded lead-acid batteries produce hydrogen gas during charging through electrolysis; hydrogen is highly flammable and can form explosive mixtures with air, requiring ventilation to prevent accumulation.
Question 3: What is thermal runaway in a VRLA battery, and what typically triggers it?
- Normal heat produced during engine cranking that dissipates after starting
- A self-reinforcing condition where increasing temperature causes increasing current, leading to battery destruction (Correct answer)
- The process of a battery warming up to optimal operating temperature in cold weather
- Overheating of the charging cables due to excessive resistance
Correct answer: A self-reinforcing condition where increasing temperature causes increasing current, leading to battery destruction
Thermal runaway occurs when elevated battery temperature reduces internal resistance, causing more current to flow, which generates more heat in a destructive feedback loop that can result in battery failure or fire.
Question 4: How does low ambient temperature affect a lead-acid battery's available capacity?
- Capacity increases proportionally with decreased temperature
- Capacity remains constant regardless of temperature
- Capacity decreases significantly as temperature drops below 32°F (0°C) (Correct answer)
- Capacity increases slightly then drops sharply below −20°F
Correct answer: Capacity decreases significantly as temperature drops below 32°F (0°C)
Cold temperatures increase electrolyte viscosity and slow electrochemical reactions, significantly reducing available capacity — a battery may deliver only 50% of its rated capacity at 0°F compared to 77°F.
Question 5: What instrument is used to measure the specific gravity of electrolyte in a flooded lead-acid battery?
- Multimeter
- Hydrometer (Correct answer)
- Clamp-on ammeter
- Ohmmeter
Correct answer: Hydrometer
A hydrometer measures the density (specific gravity) of the electrolyte relative to water, which directly correlates to the state of charge of a flooded lead-acid battery cell.
Question 6: According to NFPA 110, what is the maximum allowable crank cycle time for Level 1 emergency power supply systems before the starting system must rest?
- 5 seconds crank, 5 seconds rest, up to 3 attempts
- 15 seconds crank, 15 seconds rest, up to 3 attempts (Correct answer)
- 30 seconds crank, 30 seconds rest, up to 3 attempts
- 60 seconds continuous cranking before lockout
Correct answer: 15 seconds crank, 15 seconds rest, up to 3 attempts
NFPA 110 specifies that starter motors should crank for no more than 15 seconds, rest for 15 seconds, and repeat up to 3 times to prevent starter motor overheating while allowing successful engine starts.
Question 7: What is the purpose of a battery capacity test (load test) on a standby generator battery?
- To measure the float charging voltage under no-load conditions
- To verify the battery can deliver rated current for the required duration and confirm it is not degraded (Correct answer)
- To determine the exact amp-hour rating as labeled by the manufacturer
- To balance electrolyte levels across all cells simultaneously
Correct answer: To verify the battery can deliver rated current for the required duration and confirm it is not degraded
A capacity test applies a known discharge load and measures the battery's ability to sustain voltage above a minimum threshold for a specified time, revealing degraded capacity that float voltage alone cannot detect.
EGSA Battery and Starting Systems 2
A battery charger for a standby generator is typically sized at what percentage of the battery's amp-hour (Ah) capacity?