charger is build around a
(click to download datasheet) adjustable
The charge starts when a battery is
connected between pins JP1-JP4 or JP2-JP4
example, if a battery is connected to JP1-JP4
pins then the current that flows cause a
voltage drop to R1, then D1 causes a voltage
drop of 0,7 volts and Ô1 conducts. Then
through transistor's emitter flows a current
that comes from
Adjustment pin of LM317.
prevents current to flow from battery back
to the charging circuit. Resistors R1,R2 and R3
adjusts the charging current and it's value
is given from : Rx=(1,25 + 0,1) / I , where
x = 1,2,3.
I is 1/10
of the battery's charging capacity. For
example if battery has a rated capacity of
1700mA then É=170.
voltage must be at least 3 times the
battery's voltage. For example an input
voltage of 25V can charge a 8,4V (9V)
R3 is 1/2
Watt and R1 and R2
it's 1/4 Watt.
Download PCB in PDF