diode have same voltage same side

Discussion in 'General Electronics Chat' started by getzme4u, Aug 14, 2011.

  1. getzme4u

    Thread Starter New Member

    Aug 12, 2011
    hello sir,
    when diode ' s both side have same voltage 12v.
    e.g. 12 v 1amp adapter in one side ,then its positive leg with 1n4007 diode(forward direction ) connecting to 12 v 7 ah lead acid smf battery 's positive terminal and negative terminal of both are common .
    adapter will charge battery till battery get its full 12 v then after getting full charge diode's both side have same voltage 12 v
    then in that condition does adapter will give current to battey always or will stop current to charge battey ?

    please solve me problem soon thanks,i want to apply this in some industrial application.
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    As long as the diode is conducting, i.e. charging the battery, the voltage on the anode will be higher than on the cathode which is connected to your battery.

    If the voltage difference between anode and cathode becomes smaller than the forward voltage drop (1.1V@1A in your case) the current through the diode decreases and finally ceases. Since a battery has a self discharge and you have the diode's forward voltage drop, you won't be able to charge the battery to the same value you have on the anode.

    Btw, if it's a 12V battery, then that voltage is it's Nominal voltage, not it's Floating voltage. Floating voltage is what you charge your battery to and for a 12V/7Ah lead acid battery it may be between 13.6 and 13.8V.

    See the figure 2 in THIS datasheet.