A battery charger is not usually part of an independent power plant
because mains electricity is not usually available where an independent power plant is used. Mobile applications such as motor homes and boats may use a battery charger when mains electricity is available and it is more convenient to recharge the storage battery bank from the mains.

Charging storage batteries is a critical process; incorrect management of the charging process will damage the storage battery bank and may reduce its working life by half or more, and the storage battery bank is the most expensive single component in a hybrid independent power plant.

To get the best life from your storage batteries the charger must perform a three-stage process. Not all battery charging performs the full three-stage process.  
The very simplest battery chargers monitor the charge in the storage battery bank and stops charging it when it is fully charged. 

More complex battery chargers also disconnect the load circuit when the charge in the storage battery bank is too low, and there is likelihood of damaging it. The most sophisticated battery chargers will perform the complete three-stage charging process.