This is the scheme diagram of electric car battery charger. As shown the circuit is a conventional power supply, followed by a regulator LM338 which is controlled by an operational amplifier which is responsible for controlling the state of charge to detect the precise moment that must stop and actuate the LED indicator.
The resistive divider enables three stages, first take the reference voltage for the operational amplifier and, on the other, control the regulator LM338 through the output of op. Thus, the load shedding occurs when the current falls below Amp medium, when the circuit starts to oscillate by driving the transistor current is passed to LED causing it to glow to indicate the end of the load.
Note that the rectifier bridge is 10 amps (50V or higher voltage) so it is not for soldering on printed circuit but screwed to the metal cabinet of the computer and connect through crimpeadas terminals. The initial filter capacitor can be welded onto the plate or may be embraced in the cabinet by means of two plastic seals and welded in parallel with positive and negative terminals of the diode bridge. The power switch is the type used in percolators which are inside the neon gas lamp that lights to turn on the computer. Pay close attention to how this switch is connected since it is very common to confuse the terminals and shorting line 220. LM338 regulator must be mounted outside the printed circuit on a suitable heat sink of at least 10 x 10 cm in area. If you want, you can place a DC ammeter in series with the positive terminal of the battery for departure to visually monitor the status of load current. This instrument can be either analog or digital, but is now much more attractive digital. The positive terminal of the instrument connects to the circuit and goes into the battery negative (toward the positive terminal). 0.1 ohm resistor to be mounted on the plate, but raised 2 or 3 cm of this to prevent heat alters the pertinax. You may place a buzzer sound while the LED shines. This must be connected between the anode of the LED and emitter of the transistor and must be of the electronic type, with oscillator included therein.
To use this electric car battery charger, simply place the battery to be charged, turn on the system and press the button that starts to load. At the end the LED will illuminate and switch off the system and remove the battery terminals.