The EH-7P is a charging AC adapter that is used to charge the EN-EL15b rechargeable Lithium-ion battery while it is in the camera’s battery compartment and the camera is connected to the charger.
The EH-7P cannot be used to charge an EN-EL15 or EN-EL15a Li-ion battery. Those batteries must use the MH-25a battery charger.
The EH-7P can be used to power the camera for shooting however the EN-EL15b battery will not charge while the camera is turned on. With the camera turned off, the battery will be charged.