Cheap Current Controlled 12 Volt Battery Charger Circuit Using IC 317

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.

In this article we are discussing one such circuit which is very easy and cheap by its design yet extremely accurate with its output voltage and current specs.

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 circuit diagram presented here shows how the IC LM317 ca 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desired safe range, the voltage remains at the specified level, however if the current tends to rise, the voltage is withdrawn by the IC and dropped, restricting the current rise any further and ensuring appropriate safety for the battery.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 12 volt constant current charger circuit using IC LM 317.

R1 = 240 Ohms,
R2 = 10k preset.
C1 = 1000uF/25V,
Diodes = 1N4007,
TR1 = 0-14V, 1Amp



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74 comments

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Anonymous
February 6, 2012 at 1:38 AM delete

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.

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February 6, 2012 at 9:13 AM delete

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.

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Anonymous
February 7, 2012 at 8:25 AM delete

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

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February 8, 2012 at 9:07 AM delete

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.

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February 8, 2012 at 9:08 AM delete

Please send it to my email hitman2008@live.in

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Anonymous
February 14, 2012 at 7:57 AM delete

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

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February 14, 2012 at 9:11 AM delete

Hi,

Yes you may do it.
Regards.

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February 14, 2012 at 11:25 AM delete

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!!

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February 14, 2012 at 12:33 PM delete

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.

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June 23, 2012 at 2:02 PM delete

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

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June 23, 2012 at 2:18 PM delete

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

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June 23, 2012 at 2:34 PM delete

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
http://homemadecircuitsandschematics.blogspot.in/2012/02/how-to-make-current-controlled-12-volt.html
by changing it to 388,then plese let me inform what is Rc in that
Thanks

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June 23, 2012 at 8:32 PM delete

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

http://homemadecircuitsandschematics.blogspot.in/2012/02/how-to-make-automatic-12-volt-battery.html

Regards.

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June 23, 2012 at 8:34 PM delete

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

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August 24, 2012 at 12:46 PM delete

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

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August 24, 2012 at 3:36 PM delete

Hi Debasis,

Use LM338 IC.

Regards

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August 24, 2012 at 3:37 PM delete

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

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Anonymous
August 27, 2012 at 6:43 PM delete

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

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August 29, 2012 at 8:34 AM delete

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

Regards.

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September 23, 2012 at 9:08 AM delete

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.

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September 23, 2012 at 9:50 AM delete

Hi April Boy,

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

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December 7, 2012 at 12:04 PM delete

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...

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December 7, 2012 at 4:10 PM delete

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.

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December 8, 2012 at 1:16 PM delete

Modem Power Requirements:
12v DC 1.5A

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

thanks!

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December 8, 2012 at 2:22 PM delete

Dear Bro,

Please see the second circuit posted on this page:

http://homemadecircuitsandschematics.blogspot.in/p/forum.html

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December 8, 2012 at 11:52 PM delete

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!

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December 9, 2012 at 12:50 PM delete

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

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December 20, 2012 at 5:20 PM delete

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

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December 20, 2012 at 5:28 PM delete

i am trying to make electric fence so please help me for that ,
i read your link :http://homemadecircuitsandschematics.blogspot.in/2012/05/make-this-solar-powered-fence-charger.html

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 ?

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December 20, 2012 at 9:21 PM delete

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

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December 20, 2012 at 10:02 PM delete

make the last circuit shown in this article:

http://homemadecircuitsandschematics.blogspot.in/2012/11/high-current-transistor-tip36-datasheet.html

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January 24, 2013 at 9:06 PM delete

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

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January 25, 2013 at 9:00 AM delete

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..

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Anonymous
May 14, 2013 at 11:57 AM delete

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

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May 14, 2013 at 9:22 PM delete

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

http://homemadecircuitsandschematics.blogspot.in/2012/04/how-to-make-solar-battery-charger.html

this circuit is better than the above.

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Anonymous
June 11, 2013 at 8:35 AM delete

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

regards
thararka

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Anonymous
June 11, 2013 at 12:40 PM delete

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..

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June 11, 2013 at 5:19 PM delete

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

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June 11, 2013 at 5:22 PM delete

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

http://homemadecircuitsandschematics.blogspot.in/2012/11/high-current-transistor-tip36-datasheet.html

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June 13, 2013 at 8:40 PM delete

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

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Anonymous
June 13, 2013 at 8:48 PM delete

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

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June 14, 2013 at 11:29 AM delete

Hi Haritop,

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

http://homemadecircuitsandschematics.blogspot.in/2012/07/making-simple-smart-automatic-battery.html

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June 14, 2013 at 11:51 AM delete

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

what is your output current requirement?

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Anonymous
June 17, 2013 at 1:49 PM delete

sir, i jst want to get 5A output

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June 17, 2013 at 9:03 PM delete

use LM338 in place of LM317 for getting 5amp.

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June 25, 2013 at 9:56 AM delete

Can i use a 12v 5a transformar
please help me

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June 25, 2013 at 2:01 PM delete

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

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August 4, 2013 at 1:00 PM delete

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

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August 5, 2013 at 10:05 AM delete

capacitor voltage rating must be twice that of transformer rating.

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Anonymous
August 10, 2013 at 9:50 PM delete

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

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August 11, 2013 at 7:07 PM delete

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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Anonymous
August 11, 2013 at 10:45 PM delete

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

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August 12, 2013 at 12:16 PM delete

Hi,

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

http://homemadecircuitsandschematics.blogspot.in/2013/06/universal-high-watt-led-current-limiter.html

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.

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August 12, 2013 at 12:17 PM delete

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

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Anonymous
August 12, 2013 at 11:38 PM delete

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

Simon

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Anonymous
August 13, 2013 at 11:19 PM delete

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

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August 14, 2013 at 11:18 AM delete

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:

http://homemadecircuitsandschematics.blogspot.in/2011/12/make-hundred-watt-led-floodlight.html

The parts would be as follows:

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

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April 23, 2014 at 4:07 PM delete

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..

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April 24, 2014 at 12:54 PM delete

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

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April 24, 2014 at 12:56 PM delete

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

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April 24, 2014 at 1:16 PM delete

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..

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April 24, 2014 at 8:50 PM delete

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.

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August 23, 2014 at 1:54 AM delete

What is Rc in above circuit! need help?

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October 15, 2014 at 1:08 PM delete

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 !

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October 15, 2014 at 6:23 PM delete

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.

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March 30, 2015 at 11:24 PM delete

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

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March 31, 2015 at 3:15 PM delete

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

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April 11, 2015 at 9:09 PM delete

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 ?

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April 11, 2015 at 9:34 PM delete

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.

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August 29, 2015 at 1:32 PM delete

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

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August 30, 2015 at 5:09 PM delete

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

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