Open Circuit Voltage, Measuring

Open Circuit Voltage, Measuring

Special Tools and Equipment







- VAG 1526A


WARNING!
Battery plugs must always be threaded in so they seal properly for charging, voltage measurement and load measurement.

Make sure the following notes are observed, since a proper measurement can otherwise not be ensured.


NOTE:
- If the open-circuit voltage is being measured on a battery installed in a vehicle, it is imperative to disconnect the Ground (GND) strap.
- Power-consuming devices must not be connected to the battery for at least 2 hours before the measurement is taken.
- Loads may not be applied to the battery for at least 2 hours before the measurement is taken.


Procedure


NOTE:
- Obtain radio code before disconnecting battery.
- Be sure to activate vehicle features (radio, clock, electric window regulator, engine) when the battery is re-connected.







- Remove cover above the battery (arrows).


NOTE: For vehicles without separate battery cover: Remove plenum cover.







- Disconnect battery Ground (GND) strap (arrow) with the ignition switched off.
- Measure voltage between the battery terminals.
- If meter indicates 12.5 volts or more, battery is in good condition.
- The battery's resting voltage should never fall below 12.5 volts, if it does, the battery should be recharged immediately. Battery, Charging
- Measure voltage between the battery terminals again.
- The battery resting voltage may not fall below 12.7 volts
- If the resting voltage is not OK, replace battery.