Battery Test

This procedure tests the battery condition and charging system of a 2008 Dodge Viper to determine if the battery requires replacement or if charging system issues exist.

Warnings

Tools required

Preparation

1. Park vehicle on level surface and apply parking brake
2. Turn off all electrical accessories including lights, radio, and climate control
3. Turn ignition to OFF position and remove key
4. Allow vehicle to sit with all systems off for at least 30 minutes prior to testing for accurate resting voltage readings
5. Open hood and locate battery in engine compartment on passenger side near firewall

Procedure

1. 1

   Inspect battery condition
   Visually inspect the battery for physical damage, cracks in the case, corrosion on terminals, and electrolyte leaks. Check that the battery hold-down clamp is secure. Note the battery date code - batteries older than 4-5 years are more likely to fail testing. Clean any corrosion from terminals using a wire brush if necessary before proceeding with electrical tests.
2. 2

   Test resting voltage
   Set digital multimeter to DC voltage. Connect the red probe to the positive battery terminal and black probe to the negative terminal. Record the voltage reading. A fully charged battery should read 12.6-12.8 volts. 12.4 volts indicates approximately 75% charge, 12.2 volts indicates 50% charge, and below 12.0 volts indicates a discharged or defective battery. If voltage is below 12.4 volts, the battery should be charged before proceeding with load testing.
3. 3

   Check for parasitic draw (if battery drains when parked)
   If the vehicle exhibits battery drain symptoms, test for parasitic draw. Ensure all doors are closed, lights are off, and all accessories are off. Disconnect the negative battery cable. Set multimeter to DC amperage (10A scale initially). Connect multimeter in series between the negative battery cable and negative terminal. Wait 2-3 minutes for all vehicle modules to go to sleep. Normal parasitic draw should be below 50 milliamps. Draw above 100 milliamps indicates a potential electrical drain issue that should be diagnosed separately.
4. 4

   Perform battery load test
   Reconnect negative cable if it was removed for parasitic draw testing. Using a battery load tester or electronic battery analyzer, follow the tester manufacturer's instructions to apply a load test. For a load tester, apply a load equal to half the battery's cold cranking amp (CCA) rating for 15 seconds. The voltage should not drop below 9.6 volts during the test at 70°F or above. For an electronic analyzer, enter the battery's CCA rating as marked on the battery label or per the vehicle's factory specification, and follow prompts. The tester will indicate Pass, Charge and Retest, or Replace.
5. 5

   Test charging system output
   Start the engine and allow it to idle. Connect the multimeter to the battery terminals with red probe on positive and black probe on negative. With engine at idle, voltage should read 13.8-14.5 volts, indicating the alternator is charging. Increase engine speed to approximately 2000 RPM and verify voltage remains in the 13.8-14.5 volt range. Turn on major electrical loads (headlights, blower motor on high, rear defrost) and verify voltage does not drop below 13.5 volts. Voltage below 13.5 volts under load or above 15.0 volts indicates a charging system problem requiring further diagnosis.
6. 6

   Perform starter circuit voltage drop test (if cranking is slow)
   If the vehicle exhibits slow cranking symptoms, perform a voltage drop test on the starter circuit. Set multimeter to DC voltage. Connect the red probe to the positive battery terminal and black probe to the starter motor positive terminal (B+ stud on starter). Have an assistant crank the engine while observing the voltage reading. Voltage drop should not exceed 0.5 volts. Excessive voltage drop indicates high resistance in the positive side of the starter circuit due to corroded connections or damaged cables. Repeat test on negative side by connecting red probe to negative battery terminal and black probe to starter motor housing. Voltage drop should not exceed 0.3 volts.
7. 7

   Document test results
   Record all test results including resting voltage, load test outcome, charging system voltage at idle and under load, and any voltage drop measurements. Compare results to specifications. A battery that fails load testing or shows voltage below 12.4 volts after charging should be replaced. Charging system voltage outside the 13.8-14.5 volt range indicates alternator or voltage regulator issues. Excessive voltage drop in starter circuit indicates cable or connection problems requiring repair.

Reassembly

1. No disassembly is required for this testing procedure
2. If battery terminals were cleaned, apply a light coating of dielectric grease or battery terminal protector to prevent future corrosion

Verification

• Verify all test results are documented and compared against specifications
• If battery passed all tests and charging system voltage is within specification (13.8-14.5V), battery and charging system are functioning properly
• If battery failed load test or shows low resting voltage after charging, battery replacement is required
• If charging system voltage is out of specification, further diagnosis of alternator, voltage regulator, or wiring is required

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle