Based on a 555, this 80's American documentation circuit detects the voltage of a battery and can then disconnect the charger. The transistor may be a general purpose type.
This circuit came out in an English publication of 1976, but it can be easily assembled using...
This interesting circuit was found in a 1968 documentation. The transistor can be a...
This circuit uses a Hall sensor in the feedback of signals that produce oscillations. The circuit is...