EGSA Battery and Starting Systems 1 — Questions and Answers
Question 1: What does the Cold Cranking Ampere (CCA) rating of a battery indicate?
- The battery's capacity in amp-hours at 77°F
- The current the battery can deliver for 30 seconds at 0°F while maintaining at least 7.2V (Correct answer)
- The maximum charging current the battery can accept
- The battery's reserve capacity at 25 amps discharge
Correct answer: The current the battery can deliver for 30 seconds at 0°F while maintaining at least 7.2V
CCA is defined as the discharge load in amperes that a battery can sustain for 30 seconds at 0°F (−18°C) while maintaining a terminal voltage of at least 7.2V for a 12V battery.
Question 2: What is the correct specific gravity reading for a fully charged lead-acid battery cell at 77°F (25°C)?
- 1.100 to 1.150
- 1.175 to 1.200
- 1.265 to 1.285 (Correct answer)
- 1.300 to 1.350
Correct answer: 1.265 to 1.285
A fully charged lead-acid battery cell should have a specific gravity between 1.265 and 1.285 when measured at the standard reference temperature of 77°F (25°C).
Question 3: What is the primary purpose of a battery equalizing charge?
- To quickly charge a deeply discharged battery
- To balance cell voltages and reverse sulfation in flooded lead-acid batteries (Correct answer)
- To reduce battery temperature during high-load operation
- To test battery capacity under full load conditions
Correct answer: To balance cell voltages and reverse sulfation in flooded lead-acid batteries
An equalizing charge applies a controlled overcharge to balance cell voltages across a battery string and help reverse mild sulfation that accumulates during normal cycling.
Question 4: When two 12V, 100 Ah batteries are connected in series, what is the resulting voltage and capacity?
- 12V, 200 Ah
- 24V, 100 Ah (Correct answer)
- 24V, 200 Ah
- 12V, 100 Ah
Correct answer: 24V, 100 Ah
Series connections add voltages while keeping capacity the same, so two 12V 100 Ah batteries in series produce 24V at 100 Ah.
Question 5: Which type of starting motor is most commonly used on diesel generator sets due to its high torque at low speeds?
- Permanent magnet motor
- Series-wound DC motor (Correct answer)
- Shunt-wound DC motor
- Compound-wound AC motor
Correct answer: Series-wound DC motor
Series-wound DC motors produce maximum torque at startup and low speeds, making them ideal for engine cranking applications where high breakaway torque is required.
Question 6: What is the recommended float voltage for a 12V sealed valve-regulated lead-acid (VRLA) battery?
- 11.8 to 12.0V
- 12.6 to 12.8V
- 13.5 to 13.8V (Correct answer)
- 14.4 to 14.7V
Correct answer: 13.5 to 13.8V
VRLA batteries are typically maintained on float charge between 13.5V and 13.8V for a 12V battery to keep them fully charged without overcharging.
Question 7: What is the function of a battery disconnect switch on a standby generator set?
- To regulate the charging voltage from the alternator
- To isolate the battery from the DC system for maintenance or to prevent parasitic drain (Correct answer)
- To control the rate of discharge during engine cranking
- To synchronize battery voltage with the AC output of the generator
Correct answer: To isolate the battery from the DC system for maintenance or to prevent parasitic drain
A battery disconnect switch allows safe isolation of the battery from all DC loads and chargers for maintenance, troubleshooting, or long-term storage to prevent parasitic discharge.
EGSA Battery and Starting Systems 1
What does the Cold Cranking Ampere (CCA) rating of a battery indicate?