12v Battery Charger Circuit with Auto Cut off

Discussion in 'General Electronics Chat' started by green90, Oct 10, 2015.

  1. green90

    Thread Starter New Member

    Sep 3, 2015
    i saw this cct in circuit gallery and i have some question about it

    1-what will be the voltage on( cv or pin 5)coz it internally connect to voltage divider
    2-i think red led always on ..then what is purpose of it ?

    • Positive terminal of the upper comparator of 555 is connected with reference voltage in order to turn OFF the charger if the battery charges above 13.8V.
    • why they said Positive terminal ?????? i think ( cv or pin 5) is negative terminal

  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    It is another stupid circuit concocted by a newbie. The use of a 555 as a Schmitt-Trigger is not novel.

    How long do you think it will take to recharge a standard 65Ah automotive battery by passing the current through a 5Ω resistor? It's maximum current delivery will be about 200mA.
    green90 likes this.
  3. dl324

    AAC Fanatic!

    Mar 30, 2015
    Definitely one of the poorer ones I've seen...

    200mA isn't even sufficient for trickle charging; let alone charging hard enough and long enough to minimize sulfation.
    green90 likes this.
  4. samy555

    Active Member

    May 24, 2010
    1- V at pin 5 = zener voltage = 5.1V
    2- It is here to indicate that the charger is on, i.e connected to the power and not related to batt state
    green90 likes this.
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    ...if it survives having a 555 supply voltage greater than the rated absolute maximum.
    green90 likes this.