A DIY charger for 12V battery

Hello makers!

The schematic presented in this project is actually a constant current source to which a current limiting section composed of Q1, R2 and R3 has been added.

The moment the current required for charging is exceeded, it is diverted through Q1 and the output voltage drops. The output voltage is: 1.2x (RV1+R5+R4)/R4 volts. The current limiting occurs when the current is approximately 0.6/R3 amps.

For a 6V battery that requires a faster charge, the charging voltage is 3x2.45=7.35V (3 cells, at 2.45V per cell). So the total value for R5+RV1 is then about 585 Ohms. For a 12V battery the value for R5+RV1 is 1290 Ohms.

For the power supply to work efficiently the input voltage must be at least 3V higher than the output voltage needed to charge the battery.

RV1 is a standard potentiometer capable of handling enough watts for the application in which the circuit is used.

The LM317 must be cooled with a sufficiently large heat sink (ultimately it depends on how much you ask of it).

Except for the situation when the circuit is used for charging car batteries or accumulators, it can also be used as a stabilized voltage source in various applications.

The diode bridge D1 is rated at 2A, and the transformer is a voltage drop from 230Vac, I don't know what voltage it has in the secondary but I trust that I did it correctly.

Gerber files and BoM for PCB are available in the download section as well.

Enjoy it! 🤓

I just designed the PCB for my own use, I am not the original author so check the source link.

*Source:

https://2.bp.blogspot.com/-ZEuHsBYY0IY/VtiDgHi8ouI/AAAAAAAAONM/aonvi6pJgT4/s1600/Incarcator%2Bbaterii%2Bauto.gif