This car battery monitor was featured in the January 1988 issue of Radio Electronics magazine. The circuit uses common transistors and has 3 levels of indication made with common LEDs.
Indicated as an amplifier block for various applications, this circuit was obtained in a 1966...
The circuit shown makes it possible to power CD-players, tape players and other devices that use 2...
I found this simple circuit in an English magazine from 1984. The circuit can be assembled easily...