Subaru Legacy BN/BS (2015-2019) Service Manual: Charge

• Do not bring an open flame close to the battery when working.

• Prior to charging, corroded terminals should be cleaned with a brush and common caustic soda solution.

• Be careful while charging the battery because it produces flammable gasses.

• Observe instructions when handling the battery charger.

• Before charging the battery on the vehicle, disconnect the battery ground terminal to prevent damage of generator diodes or other electrical units.

• The charge control feature and specifications for judgment of charge completion depend on the device. Follow the instruction manual of the charger used.

• Keep the electrolyte temperature at 45°C (113°F) or less while charging. Stop charging when the temperature exceeds this value.

• Constant current charging

This method makes it easy to charge to 100%, since the electrolyte is agitated by the gassing occurred at the end of charging. However, the time for charging is comparatively long because the current value is kept constant.

• Constant voltage charging

This method completes charging in a short period of time due to the large current. However, it is difficult to charge to 100% because no gassing occurred at the end of charging and the electrolyte is not agitated. Therefore, the combined use with the constant current charging is preferable.

• Quasi-constant voltage charging

This method is widely used for commercially available chargers.

Compared to the constant voltage charging whose charging current at the beginning of charging becomes large, it reduces the charging current by lowering the voltage at the initial stage, resulting in battery load reduction. The time for charging is comparatively long. However, this type of chargers can be manufactured comparatively inexpensive due to the simple control circuit (or manual settings). After the initial stage of charging is completed, it gradually raises the charging voltage so that the charging current is within the specification, until the battery is fully charged.

• Constant voltage/current charging

In addition to the constant voltage charging, this method controls the upper limit of the current.

The constant current charging is applied at the beginning of charging, and the constant voltage charging is applied at the end. This makes battery charge comparatively efficient in a short period of time. Charging by generators is similar to this method.

Amount of discharge (Ah) = Remaining capacity (%) calculated by specific gravity - 5 hour rate capacity (Ah)

Amount of charge (Ah) = Charging current value (A) - Time for charging

• Quick charging is accompanied by a large amount of heat generation. Charging should be completed in up to 30 minutes regardless of battery size.

• Quick charging is used to recover the battery until it can start the vehicle. For full charging, use the normal charging method.

• Keep the electrolyte temperature at 55°C (131°F) or less while quick charging. Stop charging when the temperature exceeds this value.