Battery Basics
What is the nominal voltage of a typical automotive battery?
12 volts.
Approximately what voltage should a fully charged, rested 12-volt lead-acid battery measure?
12.6–12.8 volts.
What color is typically used for the positive jumper cable?
Red.
What setting should a multimeter use to measure automotive battery voltage?
DC volts.
What does DTC stand for?
Diagnostic Trouble Code.
What does CCA stand for?
Cold Cranking Amps.
What safety equipment should be worn when working around automotive batteries?
Safety glasses or appropriate eye protection.
What color is typically used for the negative jumper cable?
Black.
How is a voltmeter connected when measuring battery voltage?
In parallel, across the battery terminals.
What connector is commonly used to connect a scan tool to a vehicle?
The OBD-II diagnostic connector, also called the DLC.
What component recharges the battery while the engine is running?
The alternator.
What does a battery load tester evaluate?
How well the battery maintains voltage while supplying a load.
Where should the final negative jumper connection normally be made?
At the manufacturer-designated ground point on the disabled vehicle, away from the battery.
Approximately what voltage might a conventional charging system produce with the engine running?
Often around 13.5–14.8 volts, although modern systems vary.
What information does freeze-frame data provide?
A snapshot of selected operating conditions when a fault was recorded.
What does reserve capacity describe?
How long a battery can supply a specified electrical load under standardized test conditions.
Why should you avoid load-testing a discharged battery?
It may give misleading results and place unnecessary stress on the battery.
In what order should jumper cables normally be removed?
In reverse order of connection, following the vehicle manufacturer's procedure.
Why should resistance normally be measured only on a de-energized circuit?
External voltage can damage the meter or cause inaccurate readings.
What is live data on a scan tool?
Current operating information reported by vehicle control modules.
Name three common automotive lead-acid battery types.
Flooded, AGM, and EFB.
Why should a cracked, leaking, or frozen battery never be load-tested or jump-started?
It presents serious acid, explosion, and injury hazards.
Why should you consult service information before jump-starting a modern vehicle?
Some vehicles require designated connection points or have special procedures to protect the vehicle and its electrical systems.
A vehicle measures 12.5 volts with the engine off and 12.3 volts while running. What should you investigate?
A possible charging-system problem, while checking the manufacturer's system design and test procedure.
Why should a technician not automatically replace the component named in a DTC description?
The code identifies a detected condition or circuit/system problem, not necessarily the failed component.