What is Proper Battery Voltage?

[GeoPappas]

I have searched the boards and have found different opinions on what proper battery voltage should be.

What should battery voltage be with the engine off?

What should battery voltage be with the battery running?

 

[Heywood]

Was actually harder to find than I first though. This is the generally offered information on the subject:

Start the car.
Test voltage across the battery terminals while the car is running.
Should be ~13.7-14.2VDC, if not, bad alternator or wiring/megafuse/grounds.

Shut the car OFF, turn on the headlights for 60 seconds.
test battery voltage across the terminals
should still be at or above 12.0VDC. If not, bad battery.

 

[GeoPappas]

Thanks for the reply.

Where did you get the info from?

During my search, I found the following voltage ranges for the battery while the car was running:

13.2 - 14.0
13.8 - 14.2
14.0 - 14.5

Yours is close to the second range.

Anyone else have any thoughts on this?

 

[contourspd98]

I would say that while the car is running it should be between 13.5-15V. And do as said before with the car off turn the headlights on for 60 seconds and then check voltage. The voltage shouldn't be less that 12.5V. At least that what my school said.

 

[Big Jim]

A fully charged battery with the surface charge removed (lights on for 60 seconds) should be between 12.4 and 12.6 volts. This is the base voltage. With the engine running at about 2000 RPM and no electrical load, the voltage should be .5 to 2.0 volts above the base voltage. The lower the battery charge, the lower the 2000 RPM voltage. Ideally, you should see about 14.6 volts with no added electrical load (lights off, heater A/C blower off, etc).

A very healthy charging system (including an exceptional battery and robust sized alternator may even be able to hold 14.6 volts at 2000 RPM with the heater blower on full and lights on high beam, but this is sort of an ideal situation if the component parts are optimally selected.

I hope this helps.

 

[projectSHO89]

Charging system test procedure.

Charging system test procedure.

Straight from the 96 service manual:

Base Voltage Test

NOTE: Prior to running this test, turn the headlamp bulbs (13007) on for 10-15 seconds to remove any surface charge from the battery. Then, wait until the voltage stabilizes before performing the base voltage test.



With the ignition off and no electrical loads on, connect the negative (-) lead of Rotunda 73 Digital Multimeter 105-R0051, or equivalent, to the battery ground cable (14301) clamp.

Connect the positive (+) lead of the voltmeter to the battery to starter relay cable (14300) clamp.

Read and record the battery voltage shown on the voltmeter. This is called base voltage and will be used in later tests.


No-Load Test

Connect Rotunda 88 Digital Multimeter 105-R0053 or equivalent to monitor engine speed.

Connect the leads of Rotunda 73 Digital Multimeter 105-R0051 or equivalent across the battery terminals.

Read the voltage (base voltage).

Start the engine (6007).

Run the engine at 1500 rpm with no electrical load.

Read the voltage. The voltage should be in the range of 14.1 to 14.7 volts. If the voltage increase is less than 2.5 volts over the base voltage, perform the following Load Test. If there is no voltage increase or the voltage increase is greater than 2.5 volts, perform the generator on-vehicle tests and generator bench tests in the Diagnosis and Testing portion of this section.


Load Test


With the engine running, turn the air conditioner on, if equipped, the blower motor (18527) on high speed and the headlamps (13008) on high beam.

Increase the engine speed to approximately 2000 rpm. The voltage should increase a minimum of 0.5 volt above the base voltage. If the voltage does not increase as specified, refer to Generator On-Vehicle Tests and Generator Bench Tests in the Diagnosis and Testing portion of this section.

If the voltage increased as specified, the charging system is operating normally. Proceed to the following battery tests.

Steve