For 1990-2009 cars only
- Measure the battery voltage at the battery terminals using a digital multimeter.
- Set the battery charger on the highest setting.
- If necessary, disable the polarity protection circuitry:
- The required battery charge time varies according to the voltage capabilities of the battery charger. A charger of less than 14 volts could take up to 16 hours before the battery appears to be accepting current.
- To determine the amount of hours the battery may need to be charged, the following calculation can be made:
- When the green dot appears in the hydrometer, discontinue charging.
- If the green hydrometer dot is not visible after an ampere-hour charge equal to twice the reserve capacity rating, replace the battery. Refer to Battery Replacement
- After charging, load test the battery. Refer to Battery Not Operating Properly .
| • | A reading of less than 11 V indicates that the initial charging will be very low. |
| • | It could take some time before the battery accepts current in excess of a few milliamperes. |
| • | This circuitry, available on most chargers, prevents charging unless the charger leads are properly connected to the battery terminals. |
| • | A completely discharged battery may not have enough voltage to activate this circuitry, even though the leads are properly connected, implying that the battery will not accept a charge. |
| • | Most chargers have an override or a bypass function so that the charger will turn ON and charge a low voltage battery. |
| • | The reserve capacity rating on the battery label is the number of ampere-hours of charge required in order to produce the green hydrometer dot. |
| • | After the meter on the charger starts to show current flow, note the number of amps being accepted. |
| • | Determine the reserve capacity of the battery. Refer to Battery Temperature Versus Voltage Drop . |
| • | Divide the reserve capacity by the number of amps shown on the meter to determine how many hours of charging is needed. |
