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Current Controlled 12V Battery Charger Circuit Using IC 317

Current Controlled 12V Battery Charger Circuit Using IC 317

In this article we are discussing a current controlled 12V battery charger circuit which is very easy and cheap by its design yet extremely accurate with its output voltage and current specs.



Why Current Control is Crucial

Charging any type of chargeable battery can be critical and involves some attention to be paid. Especially the current or the rate at which the battery is being charged becomes an important factor as far as maintaining life and efficiency of the battery for a longer period of time is concerned.

We all know how smart the IC 317 is and it’s no surprise why this device finds so many applications requiring precise power control.

The Current Controlled 12V Battery Charger Circuit Using IC 317 presented here shows how the IC LM317 can be configured using just a couple resistors and an ordinary transformer bridge power supply for charging a 12 volt lead acid battery with utmost accuracy.

How it Works

The IC is basically wired in its usual mode where R1 and R2 are included for the required voltage adjustment purpose.

The input power to the IC is fed from an ordinary transformer/diode bridge network; the voltage is around 14 volts after the filtration via C1.

The filtered 14 V DC is applied to the input pin of the IC.

The ADJ pin of the IC is fixed to the junction of the resistor R1 and the variable resistor R2. R2 can be fine set for aligning the final output voltage with the battery.

Without the inclusion of Rc, the circuit would behave like a simple LM 317 power supply where the current wouldn't be sensed and controlled.

However with Rc along with BC547 transistor placed in the circuit at the shown position makes it capable of sensing the current that’s being delivered to the battery.

As long as this current is within the desired safe range, the voltage remains at the specified level, however if the current tends to rise, the voltage is withdrawn by the IC and dropped, restricting the current rise any further and ensuring appropriate safety for the battery.

The formula for calculating Rc is:

R = 0.6/I, where I is the maximum desired output current limit.

The IC will require a heatsink for operating optimally.

The connected ammeter is used for monitoring the charge condition of the battery. Once the ammeter shows zero voltage, the battery may be detached from the charger for the intended use.

Parts List

The following parts will be required for making the above explained current controlled 12V battery charger circuit using IC LM 317.

R1 = 240 Ohms,

R2 = 10k preset.

C1 = 1000uF/25V,

Diodes = 1N4007,

TR1 = 0-14V, 1Amp

How to Connect pot with LM317 or LM338 Circuit

The following image shows how the 3 pins of a pot needs to be correctly configured or wired with any LM317 voltage regulator circuit or a LM338 voltage regulator circuit:

As can be seen the center pin and any one of the outer pins is selected for connecting the potentiometer or the pot with the circuit, the third unconnected pin is kept unused.

 

How to Connect pot with LM317 or LM338 Circuit

 

Adjustable High Current LM317 Battery Charger Circuit

For upgrading the above circuit into a variable high current LM317 battery charger circuit, the following modifications can be implemented:

 

Simplified version of having an Adjustable Current with LM317

adjustable current i LM317 Ic power supply

SHARING IS CARING!


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!



61 thoughts on “Current Controlled 12V Battery Charger Circuit Using IC 317”


  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. Hi sir! dear sir i need a current control circuit using lm358 for my 10 amp-14v smps so that it may decrease its current while the battery being charged?

  3. Sir i have a question sir i have a dc burshless motor which is three wire comes from the coil.. Now u tell how to connect these three wire if any cricuit from that so u please provide me…

  4. Ok sir but in the updated diagram what rated value transistor i can used… In parallel connection for 3 to 5 amp output supply…

          • Can u explain this diagram sir… Because i confused. 0.1ohm resistance is also not available in my market sir minimum 1 ohm resistance and maximum 3mega ohm resistance are available.. Please tell which cab be used in place of it…

            • Means to say 10pic of 1 ohm 1/2watt in parallel.and also clarify me if i used 2n3055 instead of bc547 then what happen in this cricuit…

          • Can u solve one question sir.. If i connect two resistance in parallel in their wattage will be increased or not
            .. Let suppose i have 1/2watt resistance then if i connect into parallel so it can change it the wattage or not… Means to increase or not..

  5. hi swag,
    how do you get 0.6 in the above rc formula?
    if I have KN2222A transistor to replace bc547 is the same formula applied?

    thanks.

    • Hi Candra, it is the full conduction switching level of the BC547 transistor or most small signal transistor. For 2N2222 also the formula will be the same…

  6. A question on the connections of the BC547 transistor in the first circuit diagram. If the image of the BC547 is transferred directly from its respective datasheet, it would appear that the resistor Rc is connected between the base and collector. Is this correct??? Thanks.

    • Please check it again, as per the shown image it is between base and emitter and not between base and collector …..collector is connected with R2/R1 junction

  7. Hello sir,
    i want a circuit that can be used both as variable DC power supply AS WELL AS car battery charger using 24V 3A transformer. Is that feasible? if yes, plz provide me a cheap cost circuit for that. i'll be grateful.

    • Hello Shry, you can use the circuit which is shown in the above article for the mentioned applications, just replace the IC LM317 with IC LM338

  8. what is the prefered circuit to design a solar powered battery charger of 20v input and constant output of 12v and variable current?

  9. hello sir;
    nice work here.
    in regards to the circuit above, if i require output current of 1ampere, from the formula you gave R=0.6/I , if I is 1A then R is 0.6ohm. am i right sir?
    if so 0.6ohm is not readily available or how do i go about it. thanks

    • thanks Madamidola, you are correct, 0.6 ohm will allow a max current of 1 amp…you can use resistors in series parallel for getting this value,for example, you can use two 0.3 ohm in series, or two 1 ohm in parallel etc.

  10. hello swagatam majumdar,

    sir, i need 12V-5A current from 12V-7A battery, if battery gives less than 5A current than it will be automataically cut the circuit.
    can please guide me ?

    Advance Thank You.

  11. hi sir .
    mera ek fan h jise chlane ki liye 12 volts & 7 amp dc chahiye . is fan ke liye koi circuit btaye (ac ko dc mai change krna h )
    thanks

    • Hi shiv,

      use a 0-12V 10 amps transformer and make a power supply using a bridge rectifier assembly and a filter capacitor with the transformer output

  12. Hi Swagatam, May I ask what would be ideal value for the RC resistor when a 12v, 3ah transformer will be used on the above circuit to charge a 7.5ah battery ?

    • Hi Roney, here's the calculation:

      Rc = 0.6 x 10/7.5 = 0.8 ohms

      wattage = 0.6 x 0.75 = 0.45 watts

      the factor 10 may be reduced to lower levels for acquiring faster charging but is not recommended for lead acid or SMF batts.

  13. There is serios mistake – diodes should be connected btw adj and out – catod connected to out, and in and Out – catod connected to in ! In case You connect a rechargeble battery first before mains, or mains unexpectedly stop, IC will be damaged from reverse voltage !

    • without diodes it will be dangerous if the input of the IC shorted to ground… which is highly unlikely….so the above configuration is adequately safe.

  14. Hi sir Swagatam, can u please help me, i want to build a simple lead acid battery that can charge a 4Ah to 200Ah battery..I have a 12-0-12 Transformer @12 ampere, what diode should i used to have an 12amp output? i just want it simple charger only using that 12-0-12 transformer and a 2 diode..can u give me an idea what value of diode should i used suitable for 12amp transformer? for now im using a 2 6Amp Diode, but im not sure if it works for my 12amp transformer..thank you sir..

    • Hi norms,

      use a bridge network instead of two diode configuration.

      connect the bridge with the center tap and any of the outer taps of the transformer.

      Connect a 68000uF/35V capacitor across the positive/negative
      This will give an output of 15V at 12 amps suitable only for charging batteries above 100AH

    • thank you very much sir for your reply and for giving me an idea..i have another question sir, what value of diode should i used for the bridge network? i have here sir a 4 pcs DIODE 10 amp and 1 capacitor value of 10,000uf/50V..is that ok sir to boost a 12amp output? or should i used only the capacitor value you said which is the 6800uf? thank you..

    • norman, use two 10amp diodes in parallel for each diode in the bridge, or two 6A4 in parallel.

      10,000uF/50v will be very good.

  15. The above circuit is capable of delivering 1.5amps only, so not suitable for your application.

    10amps is just about the right amount of current for charging your battery, means you can directly connect the battery with the present source, it will charge it optimally within 10 to 14 hours of time.

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