The battery must not be charged or discharged for at least 2 hours before the measurement. Charging or discharging during this time will falsify the measurement result.
- Switch off the ignition and all electrical consumers, remove the ignition key.
- Remove the negative terminal from the battery.
- Wait at least 2 hours. During this period of time, do not charge or discharge the battery.
- Measure the voltage at the terminals with a multimeter that provides measurement accuracy to tenths of a volt.
Battery voltage at no load | Degree of infection | Battery status |
11.70 V | 0% | Deep discharge. Capacity is almost zero |
12.20 V | 50% | Depending on the service life, sulfation of the plates occurs, which is removed only by charging with high currents. At the same time, the plates are subjected to strong tension and may crack, which leads to increased corrosion of the positive plates |
12.35 V | 65% | In rechargeable batteries with indicator «magic eye» the indicator color changes from green to black. The battery of a new or stored vehicle needs to be charged |
12.70 V | 100% | Maximum capacity |
Measurement result | Further actions |
Voltage at no load not less than 12.5 V | Voltage at no load is normal, test the battery under load |
Voltage at no load less than 12.5V | Charge the battery |
If, after charging, the voltage at the terminals with no load is below 12.5 V, then the battery must be replaced.
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