Automotive Batteries Questions and Answers

Answer: A

A sound battery holds above 9.6 volts through a fifteen second load test at twenty five degrees. The cranking limit of 10.5 volts is genuinely used as a criterion during starter testing, which makes that option a real figure from a related test. The shared behaviour explains why these belong together and the differences explain why both exist. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: B

Cranking voltage should stay above about 9.6 volts, and a lower figure with normal starter current points to the battery. Starter current is measured too but reflects the starter and the engine, which makes the second option a related measurement wrongly attributed. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. A symptom that appears under one condition and not another is what narrows the diagnosis quickly.

Answer: C

Leaving a battery discharged lets soft sulphate crystallise into a hard form that resists conversion, permanently reducing capacity. Terminal corrosion and plate shedding are genuinely different failure modes of the same battery. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. The order in which the effects act is what decides the outcome, so it is worth establishing first. Framing the question as which quantity the change acts upon makes the answer follow without calculation.

Answer: D

Sulphation proceeds while a battery sits discharged, so a maintenance charger or periodic charging preserves it. Disconnecting the terminal does stop the drain, which makes the last option genuinely helpful though not sufficient on its own. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Checking which component actually carries the load settles most questions of this kind at once. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: A

A smart charger reduces to a float voltage once charged and can be left connected indefinitely. An unregulated trickle charger overcharges eventually and boils the electrolyte away, which is precisely why the last option is a trap. Naming what changes and what stays the same is the reliable route through questions of this shape. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Framing the question as which quantity the change acts upon makes the answer follow without calculation.

Answer: B

Charging electrolyses water into hydrogen and oxygen, and a spark near the vents can ignite it violently. Acid mist is genuinely produced as well, which makes the last option a real secondary hazard. Ventilation and no naked flames are the rules. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. The shared behaviour explains why these belong together and the differences explain why both exist. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: C

The final connection sparks, so it is made to an engine earth point remote from the vented gases. Connecting last at the flat battery is exactly the wrong thing to do. The sequence exists specifically to keep the spark away from hydrogen. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. The quantity that varies and the quantity that does not are worth naming before any substitution is attempted.

Answer: D

Removing the earth first means a spanner touching the body while loosening the positive cannot short the battery. Reconnection is the reverse. It is one of the oldest and most useful workshop conventions. The order in which the effects act is what decides the outcome, so it is worth establishing first. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision.

Answer: A

Semiconductors conduct heavily in reverse and destroy themselves within seconds, taking control units and the alternator with them. Fuses are far too slow to protect them. It is one of the most expensive errors possible. Checking which component actually carries the load settles most questions of this kind at once. Naming what changes and what stays the same is the reliable route through questions of this shape. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: B

Clocks, alarms and control units in sleep mode draw a small quiescent current, typically under fifty milliamps once everything has gone to sleep. Self discharge is a separate internal phenomenon, which makes the last option a genuinely different quantity. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Most errors here come from carrying a result across from a neighbouring case where it does not hold.