The schematic diagram:
- Assemble the circuit on a good quality PCB.
- F1 can be a 2A fuse.
- T1 can be a 230V primary, 35V/3A secondary step down transformer.
- LM317 must be fitted with a heat sink.
- If 3A Bridge is not available, make one using four 1N5003 diodes.
- 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.
- 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 battery charger is specifically designed for two 12V/7AH/6 cell lead acid batteries in series OR a 24V/7AH/12 cell lead acid battery.
Watch the video: