One of the battery fast charging circuits

Fast and efficient charging is to charge with a current that is ten to dozens times higher than that of ordinary conventional charging. When the voltage of the battery rises to
the specified value (vaporization point), the polarization phenomenon in the battery has become serious, and charging should be stopped. Then the battery is discharged with a large current instantaneously
, the voltage of the battery drops rapidly, and the polarization phenomenon disappears quickly, and then the battery is continued to be charged with a large current, and
the cycle repeats. When charging in this way, the temperature rise will not be very high, the charging speed is fast, and the efficiency can reach 90%, which can extend
the service life of the battery.
    Using fast charging , the charging time can be shortened from about 20 hours to 1-2 hours, and the electric energy can be saved by 20%-25
%.
    The circuit is shown in the figure. It can be used as a 12V car battery charger.
    Adjusting the potentiometer RPi can change the discharge time interval. When debugging, pay attention to the charge and discharge time interval to be adjusted to
suit the electrochemical reaction speed in the battery. When the battery voltage is low, the electrochemical reaction is fast, so the time interval should be shorter
; when the battery is close to full, the interval should be longer.