Five free practice questions on battery and starting systems: content area B of the ASE A6 Electrical/Electronic Systems test, 9 of its 50 scored questions (18%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A hybrid sedan has no belt-driven generator. What keeps its 12-volt auxiliary battery charged while the vehicle is in Ready mode?
- A regenerative braking circuit wired to the 12-volt battery
- The motor-generator wired straight to the 12-volt battery
- A DC/DC converter fed by the high-voltage battery
- The high-voltage battery through a voltage-dropping resistor
Show the answer
C. Correct. The DC/DC converter steps the high-voltage battery's voltage down to a regulated charging voltage for the 12-volt system, doing the job a generator does on a conventional vehicle. If the 12-volt battery keeps running down, the converter's output is checked along with the battery.
Why not the others
A. Regenerative braking returns energy to the high-voltage battery through the inverter, not to the 12-volt battery. The 12-volt battery is charged by the DC/DC converter, which draws on the high-voltage battery.
B. The motor-generator works at the high-voltage system's voltage and feeds the high-voltage battery through the inverter. It is not wired to the 12-volt battery; the DC/DC converter supplies the low-voltage system.
D. A resistor would turn most of the energy into heat and could not hold a steady charging voltage as loads change. The 12-volt battery is charged by a DC/DC converter, which regulates its output.
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A flooded battery needs water added far more often than normal. Any of these could be the cause EXCEPT:
- a charger repeatedly left on at a high rate after the battery is full.
- generator output that stays below the battery's charging voltage.
- a crack in the battery case that lets electrolyte seep out.
- high underhood heat from a battery mounted close to the exhaust.
Show the answer
B. Correct. Water is lost mainly through gassing, which charging current drives when a battery is overcharged or hot; a generator that undercharges supplies too little current for heavy gassing. It would leave the battery discharged and sulfated, not low on water.
Why not the others
A. Charging past full turns the extra energy into gassing, which splits water into hydrogen and oxygen and lowers the electrolyte level. A charger left on at a high rate after full charge could cause the frequent topping up.
C. A cracked case lets electrolyte leak away, so the level drops and has to be topped up often; look for acid residue and corrosion on the tray. This could cause the complaint, and the battery is replaced.
D. Heat speeds evaporation and gassing, so a battery near a hot exhaust loses water faster than one in a cooler location. This could cause the complaint; any heat shield the vehicle came with should be in place.
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A technician is checking battery state of charge with a hydrometer. Technician A says a reading taken right after adding water to a low cell shows that cell's true state of charge. Technician B says the same hydrometer test can be used on each cell of a sealed AGM battery. Who is right?
- A only
- B only
- Both A and B
- Neither A nor B
Show the answer
D. Correct. Technician A is wrong: added water stays on top of the electrolyte until charging mixes it, so a reading taken right away is low and misleading; charge first, then read. Technician B is wrong: an AGM battery's electrolyte is held in glass mats and the cells cannot be opened, so its state of charge is read from open-circuit voltage instead.
Why not the others
A. Not A only. Technician A is wrong because fresh water floats above the electrolyte until charging mixes it, so the reading is falsely low. Technician B is also wrong, since a sealed AGM battery has no free electrolyte a hydrometer can draw.
B. Not B only. Technician B is wrong: the electrolyte in an AGM battery is absorbed in glass mats in sealed cells, so a hydrometer cannot be used. Technician A is wrong as well, because water just added has not mixed with the electrolyte.
C. Neither technician is right. Technician A would read diluted electrolyte that has not yet mixed, and Technician B describes a test that cannot be made on sealed AGM cells; open-circuit voltage is used for an AGM battery.
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A battery mounted under the rear seat has a vent tube attached to its case. What is the tube's purpose?
- It equalizes pressure between the cells as they charge
- It drains spilled electrolyte from the battery tray
- It draws cooling air across the top of the battery
- It routes hydrogen and acid vapor out of the vehicle
Show the answer
D. Correct. A battery inside the passenger compartment or trunk can give off hydrogen and acid vapor, and the vent tube carries them outside instead of letting them build up where people sit. A missing or disconnected tube is reconnected whenever the battery is replaced.
Why not the others
A. The tube is not there to balance pressure between the cells. It connects to the battery's vent and carries the hydrogen and acid vapor the cells give off out of the vehicle, so the gas cannot collect where people sit.
B. The tube connects to the battery's vent, not to the tray, so it carries gas rather than spilled electrolyte. Its purpose is to route hydrogen and acid vapor out of the vehicle.
C. The tube is too small to move cooling air and is connected to the vent, not open around the case. It carries hydrogen and acid vapor from the battery to the outside.
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A technician is measuring starter current draw with an inductive amp clamp around the battery cable. Technician A says the draw is the peak reading at the instant the starter engages. Technician B says the ignition or fuel system is disabled so the engine cranks without starting. Who is right?
- A only
- B only
- Both A and B
- Neither A nor B
Show the answer
B. Correct. Technician B is right: the engine must keep cranking for several seconds without starting so a steady draw can be read and compared with the specification. Technician A is wrong: the brief surge as the motor starts turning is far higher than the cranking draw, so the reading is taken once cranking settles.
Why not the others
A. Not A only. Technician A is wrong: the momentary inrush when the starter engages is much higher than the steady cranking draw the specification describes. Technician B is right that the engine is kept from starting so the draw can be read while it cranks.
C. Only Technician B is right. Disabling ignition or fuel lets the engine crank steadily for the reading, but Technician A would record the brief inrush surge, which is much higher than the cranking draw.
D. Technician B is right: the engine is kept from starting so a steady cranking draw can be read. Technician A is wrong, because the peak at engagement is a momentary surge, not the cranking draw.
02Answer key
| Question | Answer |
|---|---|
| Q1 | C |
| Q2 | B |
| Q3 | D |
| Q4 | D |
| Q5 | B |
03What area B covers
This content area covers the 12-volt battery and the starting system. It takes in battery types and multi-battery setups, state-of-charge, load and conductance testing, charging, keeping module memory alive during a battery swap, cables, hold-downs and vent tubes, jump-starting, and diagnosing a slow crank or no-crank with current draw and voltage drop tests, including telling electrical faults from mechanical ones.
The ASE test specification calls this content area “Battery and Starting System Diagnosis and Repair”. It carries 9 of the 50 scored questions, 18% of the test.
- Identify battery type, voltage and multi-battery wiring
- Test state of charge, load capacity and conductance
- Charge batteries and keep module memory during service
- Service cables, clamps, hold-downs, trays and vent tubes
- Jump-start safely with cables or a booster
- Measure starter current draw and circuit voltage drops
- Test starters, relays, solenoids and control circuits
- Separate electrical from mechanical cranking faults
04What the questions turn on
Charge before you load test
A load test means something only on a battery charged to the level the procedure requires, since a good battery at half charge can fail. Charging leaves a surface charge that makes open-circuit voltage read high, so it is bled off first.
Low draw versus high draw
Slow cranking with starter draw below specification means resistance is limiting current, so the next step is voltage drop testing both sides of the circuit while cranking. High draw with good circuits points to an engine that is hard to turn.
Where the meter leads go
A voltage drop reading covers everything between the two leads. Leads on the positive post and the starter battery terminal take in the cable and both end connections. On the ground side, the engine-to-negative-post reading has its own limit.
Parallel batteries stay at 12 volts
Two batteries joined positive to positive and negative to negative are in parallel: voltage stays at 12 volts and capacity adds. Each is disconnected and tested on its own, because a connected partner carries part of the load and masks a weak one.
05The other content areas
The A6 test has five content areas. Each has its own page of free questions:
The ASE A6 Electrical/Electronic Systems practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.