battery charging circuit

Discussion in 'General Electronics Chat' started by kppp, Jul 21, 2008.

  1. kppp

    Thread Starter Member

    Apr 23, 2008
    I am implementing a battery charging circuit for rtc, battery is used in Ni-MH
    Circuit is:
    Vcc=5v connected to p-junction of diode, n-junction of diode is connected to resistor and resistor is connected to +ve terminal of battery, -ve terminal of battery is connected to ground.

    Junction between +ve terminal of battery and resistor is used as Vbat=3v and given to rtc

    My doubt is how battery discharges i.e path for battery discharge?
    is it self discharged, or it has hardware path for discharge?
    is battery discharges through VCC when switched off or through ground?

    My system works for 10 minutes and then it hanges. And I found that Vbat=4.7V
    Then I switch off the machine and switch on after sometime, that time it works for 10 minutes and again hangs
    Is it because of charging of battery??

    thank u all...
  2. fabelizer

    New Member

    Mar 7, 2009
    rtc has a ground...

    Lithium would be the usual back up chemistry for an RTC.

    What is system Vcc? A resistor alone as a charging circuit will ruin your battery, and will try to charge it to Vcc....slowly.

    You will need to post a circuit sketch to get any real help here, but if I were you, I would find a schematic using the same RTC chip you are using, and copy the back up circuit.