I am planning a device consisting of a load, a battery, and an external power source.
The idea is that the battery powers the system until the external power is plugged in -- then, the external source provides the power and charges the battery.
I am working with a 8.2V battery pack, and would like to add an auto charging circuit to this battery, such that it start charging when the battery has been discharged a certain amount, and stops charging when the battery is fully charged.
I would like to know what is a good way to accomplish this, and what voltage source/level I should be using to charge the battery safely.