The windings in the charger do warm up under charging use, hence the fan. I also know after a long time the windings in a car alternator or starter motor will loose effectiveness as heat changes the metal of the wire so it has higher resistance. In the case of a charger with a transformer or maybe even switching type a lessened magnetic field will drop voltage.
The other of dropping of voltage immediate after removing from charger is what I've seen as normal. The reason I think is that if the voltage is not higher from the charger over the battery, there would be no current flow to charge the battery.
The settling of the voltage after a few hours after charging by some amount of less than a volt is also just normal. My underwater scooter 12 volt 6ampere hour battery is always done this and it also works fine running the motor.
The other of dropping of voltage immediate after removing from charger is what I've seen as normal. The reason I think is that if the voltage is not higher from the charger over the battery, there would be no current flow to charge the battery.
The settling of the voltage after a few hours after charging by some amount of less than a volt is also just normal. My underwater scooter 12 volt 6ampere hour battery is always done this and it also works fine running the motor.
