This lead acid battere charger circuit is designed in response to a request from
Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in
series.Anyway he did not mentioned the no of cells per each 12V battery. The no of
cells/battery is also an important parameter and here I designed the circuit assuming
each 12V battery containing 6 cells. When two batteries are connected in series, the
voltage will add up and the current capacity remains same. So two 12V/7AH batteries
connected in series can be considered as a 24V/7AH battery.
The circuit given here is a current limited lead acid battery charger built around the
famous variable voltage regulator IC LM 317. The charging current depends on the value
of resistor R2 and here it is set to be 700mA. Resistor R3 and POT R4 determines the
charging voltage. Transformer T1 steps down the mains voltage and bridge D1 does the job
of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of
current from the battery when charger is switched OFF or when mains power is not available.
Notes.
Assemble the circuit on a good quality PCB.
T1 can be a 230V primary, 35V/3A secondary step down transformer.
If 3A Bridge is not available, make one using four 1N5003 diodes.
LM317 must be fitted with a heat sink.
R2 = 0.85 ohm is not a standard value. You can obtain it by combining a 6.2 ohm and 1
ohm resistors in parallel.
F1 can be a 2A fuse.
To setup the charging voltage, power ON the charger and hook up a voltmeter across the
output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready
and you can connect the batteries.
This charger is specifically designed for two 12V/7AH/6 cell lead acid batteries in
series OR a 24V/7AH/12 cell lead acid battery.
Read more: http://www.circuitstoday.com/24v-lead-acid-battery-charger-circuit#ixzz1Pls7sC8t
