Measuring the battery's resting voltage (Audi A4 B6)

To check the battery status, you can use an accurate multimeter (reading accuracy ±0.02 V). Based on the value of the resting voltage, you can judge the battery charge level.

1. If the measurement is performed with the battery installed in the vehicle, turn off the ignition and disconnect the ground cable from the battery (grounding). Before the measurement, the battery should not be under load for at least two hours. During these two hours, the battery should not be charged either.

2. Connect the voltmeter to the battery terminals. All consumers must be switched off.

3. If the meter shows 12.5 volts or more, the battery is OK. The following table shows the relationship between the resting voltage and the battery condition.

Voltage (V)	12.66 and more	12,48	12,3
The battery is charged	100%	by 70%	by 50%

4. However, if after filling the electrolyte and charging the battery the open circuit voltage does not exceed 12.5 volts, the battery must be replaced. The voltage between the terminal clamps should be measured several times!

(The original article is available on the online resource «AUDIMANUAL.ru»)