12v Battery Charger Circuit using LM317 (12v Power Supply)

[queennikki1972]

Thinking about building this project.

https://circuitdigest.com/microcontroller-projects/12v-battery-charger-circuit-diagram-using-lm317 but I need someone to tell me if the circuit is incorrect and also decipher the BOM..

Specifically the recommended wattage for all resistors and (Diode- Nn007  (3)) Do they mean 1n4007 for example? They also mention a 0.05R - Shunt Resistor/wire but I dont see on the schematic.

I wont be using the Arduino nano or lcd

[queennikki1972]

Nevermind on the diodes, i see that it should probably be 1.5 amp diodes

[woodchips]

What a bizarre circuit!

Look in any application note for the 117 for a LA battery charger that is far more subtle. It uses a low value, 0.5 ohm or so. series resistor between the out terminal and the voltage divider going to the adjust pin. This automatically adjusts the charge current as the voltage rises, work out how!

[queennikki1972]

found it! Very simple circuit instead of this one.

http://www.ti.com/lit/ds/symlink/lm117.pdf page 24

[Zero999]

Thinking about building this project.

https://circuitdigest.com/microcontroller-projects/12v-battery-charger-circuit-diagram-using-lm317 but I need someone to tell me if the circuit is incorrect and also decipher the BOM..

Specifically the recommended wattage for all resistors and (Diode- Nn007  (3)) Do they mean 1n4007 for example? They also mention a 0.05R - Shunt Resistor/wire but I dont see on the schematic.

I wont be using the Arduino nano or lcd

Connecting an LM317 current limiter in series with a voltage regulator circuit, like that is a bad idea, because it requires a lot of voltage headroom to work. The LM317 voltage regulator circuit, needs an input voltage of about 3V more than the input. The current regulator circuit needs an additional 1.25V, as that voltage is dropped across the sense resistor: 4.25V. An LM317 voltage and current regulator in series, require an input voltage of around 7.25V more than the output voltage. Then the diode on the output will drop even more voltage.

A 12V transformer is much to low for this circuit. It needs an 18V transformer to stand any chance of working properly.

found it! Very simple circuit instead of this one.

http://www.ti.com/lit/ds/symlink/lm117.pdf page 24

Yes, that's a better idea. Figure 34, on page 26, is also a good idea, if sensing the current on the negative terminal of the battery, is acceptable.

[queennikki1972]

http://www.ti.com/lit/ds/symlink/lm317.pdf page 13 battery charging circuit "RS" means current sensing resistor? Im sorry for asking such dumb questions

[MarkF]

Here is a circuit I found online some time ago.  There was a description but I didn't save the URL.
I have not built it but looks interesting to play around with.

   

[queennikki1972]

MarkF that makes more sense to me. I assume that 1R0 is 1W means 1 WATT resistor.

[MarkF]

This is not where I initially found the circuit.  But here is a write up.
https://sites.google.com/site/donutscience/various-projects/the-easiest-diy-lithium-polymer-battery-charger/the-easiest-diy-lithium-polymer-battery-charger---a-bit-more

Here is a link to the first page.
https://sites.google.com/site/donutscience/various-projects/the-easiest-diy-lithium-polymer-battery-charger

[MarkF]

Here is the original link:  http://www.talkingelectronics.com/projects/200TrCcts/101-200TrCcts.html#84B

[digsys]

MarkF that makes more sense to me. I assume that 1R0 is 1W means 1 WATT resistor.

errr nope. 1R0 = 1.0 ohms (at 1W as stated)
Working with V=IR, as current increases, voltage across the resistor also increases following that formula. At near 0.6V ~= 600mA, it will start to conduct
and start bringing down the Vop. If you need more current, decrease the resistor value and vice-versa
Note: That type circuit is really only for "Trickle charging" at ~ 13.8V, it has no boost capability, as usually ~14.4V. That gets trickier :-)

[Zero999]

http://www.ti.com/lit/ds/symlink/lm317.pdf page 13 battery charging circuit "RS" means current sensing resistor? Im sorry for asking such dumb questions

I thought it meant series resistor, but the naming is arbitrary.

Here is a circuit I found online some time ago.  There was a description but I didn't save the URL.
I have not built it but looks interesting to play around with.

   

It's probably based around the one on the datasheet I referred to above.

http://www.ti.com/lit/ds/symlink/lm117.pdf page 26.

MarkF that makes more sense to me. I assume that 1R0 is 1W means 1 WATT resistor.

errr nope. 1R0 = 1.0 ohms (at 1W as stated)
Working with V=IR, as current increases, voltage across the resistor also increases following that formula. At near 0.6V ~= 600mA, it will start to conduct
and start bringing down the Vop. If you need more current, decrease the resistor value and vice-versa
Note: That type circuit is really only for "Trickle charging" at ~ 13.8V, it has no boost capability, as usually ~14.4V. That gets trickier :-)

He's right. It should be a 1W resistor, to allow some leeway.

[queennikki1972]

Typo, 1 Ohm at 1 watt is actually what I meant to say. 1R0 1W = 1 Ohm at 1 watt