# Working of Solar charger circuit

1. Mar 29, 2014

### NafeesAhmed

Hello everyone !
can you please tell me how this whole circuit is working ?
specially these ones,

1.whats happening at LM317's pins(in adjust and out) ?
2. whats the purpose of zener here?
3. purpose of transistor nd how is it working ?

last question!
how much time it will take to charge that 6v(4.5Ah) battery if we use 12v(3watt) solar panel?

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2. Mar 29, 2014

### davenn

3. Mar 31, 2014

### Staff: Mentor

The homework sub-forum is the correct place for posting this question (or rather, these 4 questions).

4. Mar 31, 2014

### NafeesAhmed

LOL :D its not homework

5. Mar 31, 2014

### NafeesAhmed

as far as i know to calculate output of lm 317 we use this equation
vout= 1.25*(1+R2/R1)
and in my case vout is 8.194v.
please tell me what about about the incoming voltage? why dont we consider that volatge in this equation? what if my inut volatage is around 8 volts? what would happen then?

6. Mar 31, 2014

### Staff: Mentor

Look on the datasheet for the minimum input-output differential voltage specification (sometimes called the "dropout" voltage).