12V Battery Charger

[ultimatekiller]

Greetings!
I am now doing a 12V battery charger for my final year project. I have found a circuit of it, but i counldn't explain it by my own. Can any one explain this? Thanks

Below shows the datasheet of some main components:
LM350: https://pdf1.alldatasheet.com/datasheet-pdf/view/11671/MOTOROLA/LM350/datasheet.pdf
LM301A: https://pdf1.alldatasheet.com/datasheet-pdf/view/11671/MOTOROLA/LM350/datasheet.pdf
2N2905: https://pdf1.alldatasheet.com/datasheet-pdf/view/44080/SIEMENS/2N2905/datasheet.pdf
1N457: https://pdf1.alldatasheet.com/datasheet-pdf/view/49983/FAIRCHILD/1N457/datasheet.pdf

 

[Roff]

Greetings!
I am now doing a 12V battery charger for my final year project. I have found a circuit of it, but i counldn't explain it by my own. Can any one explain this? Thanks

Below shows the datasheet of some main components:
LM350: https://pdf1.alldatasheet.com/datasheet-pdf/view/11671/MOTOROLA/LM350/datasheet.pdf
LM301A: https://pdf1.alldatasheet.com/datasheet-pdf/view/11671/MOTOROLA/LM350/datasheet.pdf
2N2905: https://pdf1.alldatasheet.com/datasheet-pdf/view/44080/SIEMENS/2N2905/datasheet.pdf
1N457: https://pdf1.alldatasheet.com/datasheet-pdf/view/49983/FAIRCHILD/1N457/datasheet.pdf

I can explain it, but I won't attempt it unless you understand feedback and op amps. Do you?

 

[Diver300]

This was discussed ad nauseum recently:-

https://www.electro-tech-online.com...needed.33539/?highlight=battery+charger+lm301

 

[soemyint]

12V Lead Acdic Battery Charger with LM350

I want to 2A 12V Battery Charger with auto cutoff. I found so many Battery chargers on website. But i haven' LM350 regulator. I want to current limit (e.g. 2A, 1.5 A, 1A....300MA) maximum of 2A. How to do?

 

[rjvh]

you can use a lm 317 and change R1 to 240Ω

I know some people that build this circuit and only chanced the lm without adjusting the resistor it was working but the data sheet for the LM317 shows in every configuration 240Ω and is recomended

the max current will be 1.5 Amp and you should cool you LM317 if you want these curents

Robert-Jan

 

[audioguru]

you can use a lm 317 and change R1 to 240Ω

No.
The more expensive LM117 uses 240 ohms. The cheaper LM317 uses 120 ohms so its output voltage doesn't rise without a load. It is shown as an LM117 with a 240 ohm resistor on the first page of the datasheet and many LM317 circuits use 240 ohms by mistake.

 

[Roff]

Just to clarify what Audioguru said:
LM317 will work with 240 ohms so long as the total output current is 10mA or more. In fact, it will work with values even higher than 240 ohms, but the output voltage is equal to

(Vref/Rref+Iadj)*Rset + Vref, where Rset is the resistor from Adj to GND,

so if you make Rref too high, Iadj will be significant and make the output voltage less predictable.
If you expect to get the correct output voltage with no load, then, as Audioguru says, you should use 120 ohms or less.