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## 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.

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.

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desired safe range, the voltage remains at the specified level, however if the current tends to rise, the voltage is withdrawn by the IC and dropped, restricting the current rise any further and ensuring appropriate safety for the battery.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

More Circuits Recommended for You...

1. hello sir Swagatam bothering again with a question ... with respect to the charger with LM317, I would like to build it but I have a 5 amp transformer and I have to charge three batteries of 12 volt / 7 amp in parallel = 21 amps as I can do? from already thank you very much.
ATTE: Amir
PS: This charger is only automatic stops.

1. Hi Amir,

Yes you can use the above circuit for charging all the three batteries in parallel using a 5 amp input current, however since the IC317 can handle a maximum of 1.5amps only, won't be suitable.
You can replace the IC317 with LM338 for the required application, though.
Make R1 120 Ohms if you are using LM338.
No this charger is not automatic, the meter will provide the charging levels of the battery and the battery should be removed once the meter shows zero current.

Regards.

2. Hello Mr. Swagatam and thanks for the answer ... I need an automatic battery charger that leave the battery connected and always charged. I want to build your project of Sine Wave UPS circuit diagram cheap. and I want to always be ready ... automatic battery charger, which would you recommend? from already thank you very much.

ATTE: amir

1. Hi Amir,

I'll surely design the circuit for you, but you will need to provide me with a detailed explanation regarding the following things:

How the circuit should work,
Complete circuit specification,
Where you will be using the circuit,
How you will benefit from the circuit.

You can add as much details as possible.

Thanks and Regards.

2. Please send it to my email hitman2008@live.in

3. sir what is rc register in lm317 3rd wire connect?

4. make the circuit given here, use LM317 in place of LM338:

this circuit is better than the above.

3. Hi. Mr. Swagatam regarding the constant current charger im looking to get 10A so can i replace lm317 for LT1038 on this circuit
regards .

1. Hi,

Yes you may do it.
Regards.

2. Hi
I'm looking for a circuit to charge a 110Ah leisure battery from a cars cigarette lighter socket. The sockets output voltage is approx. 14V when the engine is running but it can only take around 10A. Would the above circuit be suitable, without the transformer/rectifier section. What voltage would this charge the battery to and what values of R1, R2 and RC would be needed.

I am new to building circuits so can you suggest a supplier in the UK who will sell in small volumes,

Many Thanks,

Simon

3. 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.

4. Hi,
Many thanks for the reply, however I need a circuit to limit the current to 10A. If I connect the empty leisure battery straight to the supply,I am told the voltage difference will cause a much larger current to flow which will blow the fuse. I have looked at current limiting diodes but these seemingly to only be available for very low currents. Do you have any other ways of doing this?

Once again, many thanks,

Simon

5. Hi,

OK then you can try the first circuit given in this article:

The formula for calculating R1 is given in the article, it would be around 0.1 ohms, for restricting the current to 10amps.

The IC will need heavy heatsinking.

6. just forgot to mention, use LM196 for the IC, that's crucial:)

7. Hi,
Once again thanks so much for your help, I'll try to find somewhere to get the parts and build the circuit,

Simon

8. you are welcome!

9. Hi,
I've tried looking for suppliers of the LM 196 but so far have had no luck. Do you (or anybody else) know of any UK suppliers that will have it.

Thanks again,
Simon

10. If you are finding it difficult to obtain the IC, here's another design which can be tried, it uses ordinary transistors, so would be easy to get:

The parts would be as follows:

T1 = TIP35
T2 = TIP31
R1 = 15 ohm/10 watt
R2 = 0.06 ohms/10 watt

4. hi mr. Swagatam sorry to bother you! if i plan to use LT1038 do i need to change the transformer amp rate and the rectifier diodes? or it stays the same!
regards!!

1. Hi Roger,

The transformer will be obviously rated around 10 amps, because that's why you are changing the IC.
The diodes will also need to be upgraded appropriately so that it can handle up to 10 amps, make them around 15 amps each.
Regards.

5. Sir,
Can you design or modify the circuit sothat when amp reading is zero then it shut off the transformer through relay,

Thanking you,
Avisek

6. And what is the Rc,Is it resistor then how to calculate this

1. I am trying to find the right formula for calculating Rc which is a resistor.

7. Sorry for disturbing you again and again,But you have designed so many chargers,
I do have purchased one 12v 3 amp transformer,And tried one of your circuit which disconnects transformer through relay,My batteries are old 4 sla connected in parralal,Suggest me a circuit which will be better for me,
Should i try
by changing it to 388,then plese let me inform what is Rc in that
Thanks

1. All the circuits are equally good, however you can try the circuit shown in the following link:

Regards.

8. Hi sir i am designing a circuit to charge a 12 volt 12 amp lead acid battery using constant current charging technique. I am using a 15 volt 4 Amp transformer and R2 as a 3 watt 200 E variable resistor. Kindly let me know which IC should should i use. Should i Use LM317 or LM 338.

Regards
Debasis

1. Hi Debasis,

Use LM338 IC.

Regards

2. 200 Ohm pot will not do, you will have to use the indicated value only for R2

9. Hi sir,
We need help on our project on how to make a circuit diagram of a power supply (12V); it can be anything as long as it works. For example, a 12 V battery charger.
Thank you sir!
-Simon

1. Hi Simon,
Please type "how to design power supply" on the given search box, you will find the particular article needed by you.

Regards.

10. Hi sir,
would you mind if u ask what Rc is? and is it necessary to put Rc in the circuit?.. Thanks and best regards.

1. Hi April Boy,

Rc is a current limiting resistor, may be excluded if the transformer is correctly rated as per the battery specs.

11. hello bro I want to build a 12v ups for my wifi modem
*I have one 12v 1.5amp adapter
*1 12v 7.5ah battery
please suggest me a circuit which will work perfect for this purpose...

1. Hi Bro,

Can you specify the WiFi modem power requirements, I mean its operating voltage, current etc.

Do you mean the 12 adapter is used for powering the mode?, then simply connect the battery output to the Wifi 12v input, no need of any UPS.

2. Modem Power Requirements:
12v DC 1.5A

I want to build a ups like it will work during load shedding without any interruption.

thanks!

3. Dear Bro,

4. Thanks Bro.....u r great!
What is the value of Resistor R1 on that circuit
(http://1.bp.blogspot.com/-I2zlapFq6RM/UML_NxUJy2I/AAAAAAAAB3w/27ZLDjK9C9g/s1600/simple+modem+UPS+circuit.png)

Thanks!

5. You are welcome Bro,

Try a 100 Ohm 1 watt resistor initially, let's check whether that's enough to keep the battery trickle charged or not. Otherwise you may have to employ a more sophisticated stage in between the shown circuit

12. hi sir i want to make 12 volt 7 amp power supply please help me ?

but i want only 7,000 volt so what i do nad if i want make transformer for that 7,000 then how can i make ?

1. use a 6 volt input DC for operating it, this may drop the voltage to 7KV

14. Dear Sir,
thanks a lot for the circuit I was Just searching for one, One Q, I've a panel with 36v 8 amps 250 watts, Can i use this circuit to Charge a 12v 150 Ah x 2 Bat's in series, or should I make any changes, also please tell me which circuit I could use along with this to protect the bat from Overcharging

1. Dear Premdeepak,

This circuit will not charge a 150ah battery, and also it will not withstand more than 24V input supply...this circuit cannot be modified for receiving more than 24V..

15. dear sir
can i use 5A or higher ampere transformer for above circuit.

regards
thararka

1. Dear thararka,

yes you can use it, it won't harm the circuit because the IC won't allow above 1.5amp any any condition

2. thanks for reply,so that what i to be change..

3. input current is not critical, but the voltage should not increase above 24V.

what is your output current requirement?

4. sir, i jst want to get 5A output

5. use LM338 in place of LM317 for getting 5amp.

16. Dear sir,
when i using 10A 15V transformer,what are the other equipments i have to change,please explain me,because i have 200A battery.i want simple high ampere charger..

1. the above circuit will not charge a 200ah battery,
you can try the following circuit for charging your 200ah batt:

17. Hi Swagatam, i have 220V switching power supply with DC output: 12volts(adjustable voltage), 15 Amps. I want to use to charge 12volts 9 - 40Ah battery. Could you help me to design the additional circuit so i can use my power supply as automatic 12V battery charger? It will be nice if the circuit have LED as the indicator.
Thank you

1. Hi Haritop,

you can use the circuit which is shown at the end of the following article:

18. Can i use a 12v 5a transformar

1. yes, but the output will be restricted to 1.5 amps only.

19. hi.. i tried this circuit.. but my capacitor bursts every time.. what is the reason??

1. capacitor voltage rating must be twice that of transformer rating.

20. 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..

1. 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

2. correction: the cap should be a 6800uF and not 68000uF

3. 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..

4. 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.

21. What is Rc in above circuit! need help?

1. it's the current sensing resistor

22. 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 !

1. 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.

23. Plz tell me how it will cutoff when battery get fully charged????

1. it will not cut off, it'll keep the battery under a regulated fixed supply....

24. 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 ?

1. 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.

2. Thank you so much.

25. 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

1. 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

26. 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.

1. Hello Ashish, you can refer to this diagram:

https://3.bp.blogspot.com/-tpcMrr6mqc4/V2jEkXBw5BI/AAAAAAAAOG4/rQQsa8sAVaUMxEJgjVqJZ6APIwvFKAXcwCLcB/s1600/current.png

2. sorry this is the correct one:

https://1.bp.blogspot.com/-TAfY5Ru7TPM/V2oJhs8pSQI/AAAAAAAAOHs/tbYJPkagHK8wccS_4P4IouSSPCIH1h1DwCLcB/s1600/current.png

3. sir, i want to automatic cut-off when battery gives below 12v supply and automatic
ON when battery gives 12v supply. sir, this is not battery charger.

4. Ashish, you can try the following design:

27. 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

1. 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.

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

1. you can the above explained LM317 concept,