12v Battery Charger Circuit with Auto Cut off

By
Jaseem Vp
181 Comments

This is a simple DIY charge controller schematic posted in response to a request by one of our readers on our facebook page. The main component of this auto battery charger circuit is a 555 timer which compares the voltage in the battery. It turns ON the charger if the battery voltage is below the variable preset voltage (12 volt chosen here) and turns OFF the charger if the voltage reaches 13.8 volt. The battery charging voltage of the charger can be varied by adjusting the variable resistor.
Recommented for you:

LED dot display based Battery charge level indicator circuit diagram
Simple battery charger circuit and battery level indicator with low battery recharge alarm
To understand the working of this 12 volt battery charge controller circuit you must have an idea of the internal diagram of 555. You can refer the pin out section at the bottom. You must also check charge controller using LM324 IC where you can find video demonstration too.

Automatic battery charger circuit diagram
Automatic battery charge controller circuit using 555 timerClick on the image for enlarged view

Components Required
IC 555
Transistor BC 548
Diode (6A4 x5 ,1N4007)
Zener diode (5.1V)
LED (red, green)
Capacitor 4700uF,25V
Resistor (1K x 3,820,2x10E 10W)
Variable resistor 10K
Relay 12V,10A
Transformer 230V/0-15,5A

Working
Positive terminal of the upper comparator of 555 is connected with reference voltage in order to turn OFF the charger if the battery charges above 13.8V.
Reference voltage is obtained by connecting a zener dide in series with a resistor.
If the battery voltage is greater than 13.8V, comparator output goes high and flip flop will be set. This turns OFF the transistor and the relay. For understanding relay working see How to connect relay: Relays working with animation
If the battery voltage is below the preset voltage (set by us), lower comparator will reset the flip flop. This turns ON the transistor and the relay will switch to charge the battery.
The recharge voltage (preset voltage) can set by varying the variable resistor.
Power ON is indicated by a red LED and charger ON status is indicated by a green LED.
Components pin out

Related Circuits:
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181 thoughts on “12v Battery Charger Circuit with Auto Cut off”
[email protected]’AnonymousJuly 10, 2013 at 3:35 pm
wt u mean 5E 10W

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[email protected]’YaseenJuly 13, 2013 at 12:33 am
5E 10W = 5 ohm 10 Watts

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[email protected]’bhanuApril 4, 2014 at 4:32 pm
Yes Yaseen you r right… 5E means sohm …,
me bhanu

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[email protected]’bhanuApril 4, 2014 at 4:34 pm
Anonymous
5E 10W means 5ohm 10watt…
Me bhanu

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[email protected]’ISAAC YEBOAHMay 17, 2015 at 12:08 pm
hi master, Isaac Yeboah is my name and a citizen of Ghana. I came across some your post online and decided to try one of them I mean the battery charger, but the current is too small to charge my batteries so please with due respect can u guide me of how to increase the current or please provide me a different diagram that comes out with 20amp to charge my batteries? because in all I want to design 12v 20amps battery charger. THANKS VERY MUCH FOR YOU EFFORT look forward to hear from you soon.

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[email protected]’peeOctober 3, 2015 at 1:46 pm
can I use the charger that uses the 555 time to charge a dry cell or wet cell.

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[email protected]’GAURAVJuly 22, 2013 at 1:56 pm
Hiii
howmuch prize of this circuit?

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[email protected]’AdminJuly 28, 2013 at 11:31 pm
Hi Gaurav,
To know the price of circuits, please visit our online circuit store Buy from our store

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[email protected]’walbertofulioApril 13, 2014 at 2:28 pm
hi gud evening sir can i use this ciruit above only monitoring the battery. Then when the battery reach at13.8volts i add a timer 30 minutes to on the transformer then off… when the battery down at 12.5volts it on the timer again..

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[email protected]’AnonymousJuly 23, 2013 at 7:15 pm
both the leds glow…
10k pot has no effect on output voltage
what to do???

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[email protected]’adminJuly 24, 2013 at 6:14 pm
Hi,
Please connect a diode in series as diagram, and connect battery and set the voltage level by rotating the pot, that you wants turn on the charger.

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[email protected]’muhammad shahroz nasimOctober 31, 2015 at 9:25 am
please give a circuit diagram of emergency light with automatic battery saver means that it works on a pwersupply charging stopped when batter’s charge full and start again charging when batter’s volt is low

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[email protected]’PramodOctober 15, 2013 at 4:34 am
Please Clarify which diode you are talking about?
is it shown in the above drawing?

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[email protected]’bhanuApril 4, 2014 at 4:43 pm
You follow this procedure
1)Disconnect the AC supply from the source .
2)Connect a variable DC power supply from the output of the circuit.
3)Set the variable DC power supply at 13.8v then varie the preset until the LED goes off
4)Then read the circuit description again…
ME bhanu

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[email protected]’CaloyNovember 23, 2014 at 2:26 am
in this circuit you can expect that the red LED will always glow bcause it is connected direcly from the transformers DC outputs. Only the green LED will do the on and off during charging. If on charge mode green LED glow and when fuylly charge greenLED turns off.

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[email protected]’CaloyNovember 23, 2014 at 2:31 am
Caloy
Your comment is awaiting moderation.
November 23, 2014 at 2:16 am

actually in my opinion i will not connect directly the TH to 12v from the relay, connect it to the output terminal of the VR which is the other terminals of the VR one is connected directly to +12v from the relay and the other connected to GND. And for the trigger terminal of ic555 use 33ohm 1/4w resistor connect to GND. Adjust the VR until you can reach the voltage of 13.8v. Also use capacitor 100uf/16v filter it to the relays coil terminals. Just try, hope it can help.

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[email protected]’nicoDecember 17, 2014 at 5:40 pm
does it works? because my project’s relay is rattling

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[email protected]’AnonymousAugust 6, 2013 at 4:09 pm
I have a small UPS & a 12v 75ah car battery can I use the UPS as my inverter? and will the UPS be able to charge the 12v 75ah car battery? because the normal battery in the UPS is 12v 7.0 ah.

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[email protected]’adminAugust 7, 2013 at 10:44 am
You can use UPS as inverter but it will take more time for charging of the battery. You have to use separate battery charger to charge 75ah battery.

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[email protected]’AnonymousAugust 6, 2013 at 11:57 pm
what is the charging current of this charger.how many 12V batteries can it charge at a time.
is this charger able to charge deep cycle batteries used for inverters.

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[email protected]’adminAugust 7, 2013 at 10:38 am
It is highly recommended to use your name while commenting for better response from us.

1) Charging current depends on the transformer used, here we are using 5A transformer, so the charging current is a little bit less than 5A(some loss due to the series resistance).

2) You can use any number of batteries but charging time will increase.

3)Inverter batteries (

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[email protected]’waelJanuary 18, 2015 at 1:50 am
so tell us how we can achive the 1/10 rate of charging current …sir you know that car lead acid must be charged by 1/10 of thier current for example a 22 amper per hour must be charged by a 2.2amper per hour
how we can achieve this using your design …555 is common chip and easy to find your design will be so popular if it can satsfy the golden current charging rate of 1/10 ..thanks

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[email protected]’NonsoJuly 15, 2014 at 2:24 pm
To set my preset value where do i connect my multi testing meter and should my charger be turned on while adjusting the preset value.

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[email protected]’AnonymousAugust 18, 2013 at 5:24 pm
My name is Friday, I have assembled the circuit, both LEDs glow, battery is @ 7.14V, how do I set my low battery level?

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[email protected]’anurenjhJuly 30, 2015 at 12:08 pm
Sir
it would be great if you could explain esc for bldc using back emf method.
.

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[email protected]’AnonymousAugust 24, 2013 at 2:35 pm
Am mike, sir, pls help me i dont understand hw to connect diode in serie to d circuit, and d output volt drop to battery voltage when connect wit battery. hw do i solve dis isseu thanks.

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[email protected]’adminSeptember 2, 2013 at 1:49 pm
Hi Mike,
Your question is not clear

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[email protected]’AnonymousAugust 27, 2013 at 7:35 pm
What does the shaded part of the capacitor means ?
I have the polarity problem..
Is Upper side of capacitor is positive ?

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[email protected]’adminSeptember 2, 2013 at 1:47 pm
Shaded part indicates negative terminal.

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[email protected]’AnonymousOctober 2, 2013 at 12:11 pm
Dear sir,

I made this circuit for 6 volt 4 ah battery. Taking relay connection I’m facing some problem and properly not work (auto cutoff when battery full charged).

Pls solve it for my doing the needful.

Awntg yours
Brgds – Main

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[email protected]’adminOctober 6, 2013 at 1:59 pm
You cannot use this for 6 volt battery.

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[email protected]’NonsoJuly 16, 2014 at 7:34 pm
When adjusting the variable resistor what should i use to know when the preset voltage is reached so that i can stop the adjustment.

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[email protected]’vaibhavApril 5, 2015 at 5:41 pm
Can this circuit be used to charge a 12v battery?
what does that 58% at 10k pot indicate?

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[email protected]’Johndirek KipteOctober 2, 2013 at 3:54 pm
Hi! Is it works if i will use BC 546, BC 547 or BC 549 instead of BC 548? Are they the same specifications? What are the differences?

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[email protected]’adminOctober 6, 2013 at 1:55 pm
They vary in the collector current (Ic). For BC 548 Ic=500mA, others are 100mA. So they may not be able to drive the relay.

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[email protected]’MarvellousOctober 18, 2013 at 5:24 am
Hi,
Thanks for your lecture. Will the external charger be connected in parallel with the ups in-built charger or separate?

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[email protected]’adminOctober 18, 2013 at 1:02 pm
Why do you need the external when you have in-built?

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[email protected]’MarvellousOctober 18, 2013 at 7:55 pm
I need external charger because of your advice on August 7 to an anonymous fellow.

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[email protected]’adminOctober 20, 2013 at 9:29 am
Hi Marvellous,
You cannot connect it parallel. You have to charge it separate by using (if it’s a car battery) High current adjustable power supply circuit by setting it’s output voltage to 14V.

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[email protected]’MarvellousOctober 20, 2013 at 12:41 pm
Thanks for your response. l want to use the ups as an inverter and the battery for longer period of time. What can l do then?

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[email protected]’adminOctober 20, 2013 at 2:15 pm
I cannot give any answer without seeing your UPS board. Here is my suggestion, charge the UPS battery with the external charger independently when charging is required. After charging reconnect battery to the ups board.

If you can identify the charging components of the UPS board,then you can connect external charger in paralle with the battery without removing UPS connection.
< Reply [email protected]'ShaheedDecember 10, 2013 at 1:16 pm Could you please show me a design in which you use the above circuit (12V Battery charger with auto cut off) but with a Wind Turbine DC generator motor. Thanks Reply [email protected]'FOUADDecember 17, 2013 at 7:31 am How to increase the amperage of the charger Reply YaseenJanuary 5, 2014 at 9:52 am Hi FOUAD To increase the current replace transformer with higher current type, also replace 10watt resistors with short circuit. Reply [email protected]'CaloyNovember 23, 2014 at 1:45 am Replace larger amp value of transformer, use also larger diode amp capacity and no need to use 10ohm/10w resistor just connect directly from the b+ Reply [email protected]'MatthewDecember 22, 2013 at 6:40 pm Matthew, please can I have several examples of batteries this circuit can charge? Reply [email protected]'CristianDecember 28, 2013 at 2:30 am Hi! I have a question about the current, this charger only work with battery of 75ah? can i charge another kind of battery?(45ah, 55ah,etc.) Thank for your time! Reply YaseenJanuary 5, 2014 at 9:44 am Hi Cristian It work with all 12V battery .by increasing the capacity, time taken for charging will increase,to reduce time you have to increas the current of transformer. Reply [email protected]'Hafeez AshrafJanuary 3, 2014 at 5:38 pm Hi,can the above circuit be used to charge car batteries? Reply YaseenJanuary 5, 2014 at 5:17 am Hi Hafeez Ashraf You can, but you should increase the current of the transformer used to reduce charging time…also replace the zener with 5.1V . Reply [email protected]'RonFebruary 17, 2014 at 7:00 pm can I replace the 5.1v Zener by another one with a higher voltage? Can you please suggest a specific voltage? Reply [email protected]'PeterJanuary 6, 2014 at 4:20 pm Hi sir, may i know what is the proper wattage of the resistor (1k and 820?) ? Reply YaseenFebruary 22, 2014 at 1:59 am Hi Peter Use 1/4 watt resistor. Reply [email protected]'ThayhorJanuary 10, 2014 at 8:18 am Is it possible for this circuit to charge a Nimh 9V battery? Also can the transistor be replace with C1815. Thank you. Reply [email protected]'CaloyNovember 23, 2014 at 2:03 am Yes you can replace transistor bc 548 to 2sc1815 but make sure to locate the proper transistor terminals. For bc 548 (1=emiter 2=base 3=collector), for c1815 (1=emiter 2=collector 3=base) C1815 is much better than bc548 because its (collector current) is Ic=150mA, while bc548 Ic=100mA. Reply [email protected]'adsamzyJanuary 26, 2014 at 7:56 pm Sir thanks for your innovative works, sir can this circuit work for 12v,200ah? sir if not, what are the things to replace.Thanks. Reply YaseenFebruary 22, 2014 at 3:31 am Hi Adsamzy It will work with 12v/200ah battery. Reply [email protected]'i.kFebruary 6, 2014 at 11:38 pm Dear sir,can I use this circuit to charge 24vdc and how. Reply [email protected]'aliyuFebruary 15, 2014 at 6:23 am Please can I use 12.6v,4A battery charger to charge a battery of a 12v,5A while the normal charger for the battery is 14.5v,5a Reply [email protected]'Ariel CFebruary 21, 2014 at 10:13 am There’s an errors on the actual diagram to what has been explained on this project. It says the circuit will stop charging when the battery’s voltage reached 13.8 but the zener used in the diagram was only 5.1. Zener should be between 13v to 14v, I used a series of 3v and 12v in series also with 150 ohms to achieve 13.83v on 15v 3amps power supply. Reply [email protected]'RexMarch 19, 2015 at 4:44 pm thanks! this worked out. why do the makers dont edit it?? Reply [email protected]'vickeyFebruary 26, 2014 at 12:25 pm hello Yaseen I want to use this circuit with 0 -20 5Amp TXR so plz help me and what you mean .Resistor (1K x 3,820,) plz relpy me thanks. Reply [email protected]'ahmedFebruary 26, 2014 at 11:50 pm 1. i connected this circuit with transformer 3 amper 24 volt DC timer was very hot , and output voltage 6.7 dc volt i changed resistor many times but no change and it’s still very hot Reply YaseenFebruary 27, 2014 at 1:55 am Hi Ahmed Maximum input voltage of 555 is +18V, your timer may damaged. Reply [email protected]'ahmedFebruary 28, 2014 at 1:02 pm thanks for your answer yeah timer damaged but i replaced it with another one the circuit working but it didn’t cutoff and the relay alway on thanks in advanced Reply [email protected]'aliyuMarch 3, 2014 at 5:57 pm What is the resistor 820 color cody and is the resistor rated in ohm or kilo ohms Reply YaseenMarch 10, 2014 at 5:07 pm Hi Aliyu Gray Red Black=820 ohm Reply [email protected]'MOTWEMarch 16, 2014 at 9:44 am Hi sir, is it possible for this circuit to give the output of 3.7v? Reply YaseenMarch 22, 2014 at 3:05 pm HI MOTWE You have to use LM317 to set the output 3.7 Reply [email protected]'MOTWEMarch 16, 2014 at 10:43 am Hi sir, is it possible for this circuit to give an output of 3.7V? Reply [email protected]'SanjeewaMarch 27, 2014 at 11:40 am This circuit is not working. Both led glow. Is there any modification to use this circuit? Reply [email protected]'kelMarch 28, 2014 at 9:40 pm hi sir: I connect 14 v to the circuit two LED came on but the relay keep clicking , is the relay keep click on when circuit working Reply [email protected]'abdul jalilApril 2, 2014 at 11:56 am voltage at Control voltage is 5.1 (as zener diode is used) fixed . and also battery positive (12 V)terminal is directly connected to Thrshold so Thr > 5.1 , this will show that battery is full . please give me solution what will be done here. thanks

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YaseenApril 11, 2014 at 1:09 am
Hi Abdul jalil
You have to vary the pot to change the threshold.

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[email protected]’CaloyNovember 23, 2014 at 2:16 am
actually in my opinion i will not connect directly the TH to 12v from the relay, connect it to the output terminal of the VR which is the other terminals of the VR one is connected directly to +12v from the relay and the other connected to GND. And for the trigger terminal of ic555 use 33ohm 1/4w resistor connect to GND. Adjust the VR until you can reach the voltage of 13.8v. Hope it can help.

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[email protected]’thulaniApril 7, 2014 at 8:13 am
hi sir

how did you come up with the values of these resistors and caps, i want to build one for the batteries at my work place, what was your ripple current (Idc)

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[email protected]’walbertofulioApril 13, 2014 at 2:48 pm
gud evening sir…can i use this ciruit as monitoring the battery voltage? bcoz last time i use battery alternator check to monitor the battery voltage. Then i add a timer to switch off the trasformer, when the battery down at 12.5v the transformer on again…when the battery reach at 13.8v the timer on again to cut off the trasformer..

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[email protected]’emwikApril 16, 2014 at 12:32 pm
i wana ask that how it sense that voltage in the battery is greater than 12v, plz answer in detail i have many confusion regarding this ?

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[email protected]’jayanathApril 17, 2014 at 4:01 am
dear sir i want to charge 12v 45ah batt.
1. can i use ups transformer for this?
2.the component required is written that 5 ohm and circuit shows 10 ohm 10w why so?
3. what will be the zener , diodes and other resistor values for my requirement?
thank you.

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[email protected]’sabyApril 21, 2014 at 12:33 pm
Hi. I have a question. Can i use a 12v 5 amp SMPS as input of the circuit replacing the 15v 5amp transformer
Thanks in advance.

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[email protected]’mukesh patelApril 22, 2014 at 4:00 am
12 volt 7 ah battery charger
Auto cut off
Pls send me quatation
9974889544

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[email protected]’SabyaApril 22, 2014 at 9:26 pm
hi, can i use a 12v 5amp SMPS in the place of 15v 5amp transformer?

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[email protected]’AbilityMay 10, 2014 at 2:53 pm
Sir, i want to know if it can be possible to recharge an inverter battery using same source generated from the inverter through external battery charger. Please i want know if that canbe possible. Thanks. Reply.

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[email protected]’saurabhMay 13, 2014 at 11:03 am
please explain how to connect relay…….i dont know

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KhaleelMay 13, 2014 at 1:04 pm
Hey Saurabh,
You can refer our previous article on How to connect relay. Hope it helps.

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[email protected]’saurabhMay 13, 2014 at 1:02 pm
how to charge car battery using this circuit

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[email protected]’travisMay 27, 2014 at 11:13 am
i’m only getting a 12V 3A transformer what are the ratings of the other components that i should use ?

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[email protected]’James WangJune 6, 2014 at 12:56 am
can i use this charger for flooded lead-acid type car battery with distilled water??

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YaseenJuly 4, 2014 at 9:19 am
Yes, you can try that.

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[email protected]’Muhammad MehboobJune 8, 2014 at 3:33 pm
what is mean by 6A4 diodes, 4 diodes 6 ampere or 6.4ampere diode

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YaseenJuly 4, 2014 at 9:18 am
Please refer datasheet.

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[email protected]’restieJune 10, 2014 at 11:18 am
I cant find the 5ohm 10 watt resistor in the diagram … i can see is 2 pcs 10ohm 10 watt resistor…. pls need help…tnx

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YaseenJuly 3, 2014 at 12:11 pm
We have used 2 10 Ohms instead of a 5 Ohm.

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[email protected]’SAJIDUR RAHMANOctober 27, 2015 at 9:59 am
I want to make a led bulb consisting 10 nos of LED of 4v DC each in parallel.can you please refer me a circuit diagram using stepdown transformer to get 4v DC supply from 220v/230v (generally available in india).The circuit should have sufficient longevity,cost efficient. What will be the rated watt of the Bulb?
Please kindly reply me.Thanking You.

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[email protected]’mandeepJuly 7, 2014 at 8:31 am
my UPS battery rechargable voltage is 82V but i required 110V for charging so tell me whom components are repairable

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[email protected]’AnjanJuly 12, 2014 at 6:37 pm
Where should I put my multimeter red & black Prob when I am setting The recharge voltage (preset voltage). Should I set the voltage when the battery connected or disconnected. pls reply soon. I am waiting for your reeply

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[email protected]’OdinakaJuly 14, 2014 at 8:14 pm
Odinaka by name pls can u give me a circuit of automatic change over

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[email protected]’akashJuly 15, 2014 at 5:55 am
plzz provide terminating circuit of the above shown battery charger diagram

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[email protected]’KishoreJuly 16, 2014 at 10:52 am
Hi Yaseem,

Can we ignore the 10ohm,10 watt resistor, if we ignore do the circuit have any impact on output?

Thanks

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[email protected]’madhu sairamJuly 21, 2014 at 4:49 am
whether it works for li-ion battery of 7.4v and 5.2amps

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[email protected]’Nestor ParaynoJuly 27, 2014 at 2:21 am
Dear Sir,
Good day.
Can you suggest how to modify the circuit adaptable to a 48 VDC charger.
Thanks,
Nestor

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[email protected]’prakashAugust 4, 2014 at 8:53 am
can i use 15 v 1A transformer in this cicuit

regards
Prakash

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[email protected]’habibAugust 5, 2014 at 7:38 pm
hi, what is the output Ampr?

thanks

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[email protected]’habibAugust 5, 2014 at 7:42 pm
hi
how much time does take to charge 12v 150amp battery by this charger?

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[email protected]’krishAugust 6, 2014 at 4:39 pm
Hi Sir,

I have designed this circuit and i could see both the red and green LED are glowing. Please tell me is this normal.

also i just tried tuning the pot but no effect on the circuit still both the LED is glowing. Please help me sir. Thanks

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emiellebulaw[email protected]’EmielleOctober 11, 2014 at 3:25 pm
for admin:
WHY YOU DO NOT ANSWER THIS QUESTION. Both LEDs Glow even if you vary the POT. Nothing happen honestly. I know i have a correct connection no doubt.

I HAVE READ THE ABOVE COMMENTS. YOU DIDNT ANSWER ANY THIS KIND OF QUESTION. I RUIN MY PROJECT BECAUSE I TRUST YOUR DIAGRAM. WE NEED YOUR HELP…. THANK YOU!

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[email protected]’caloyNovember 26, 2014 at 2:32 am
in this circuit you can expect that the red LED will always glow bcause it is connected direcly from the transformers DC outputs. Only the green LED will do the on and off during charging. If on charge mode green LED glow and when fuylly charge greenLED turns off.

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[email protected]’caloyNovember 26, 2014 at 2:39 am
Try this changes: Do not connect directly the TH to 12v from the relay instead connect it to the output terminal of the VR which is the other terminals of the VR is connected directly to +12v from the relay and the other connected to GND. And for the trigger terminal of ic555 use 33ohm 1/4w resistor series it to GND. Adjust the VR until you can reach the voltage of 13.8v. Hope it can help.

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[email protected]’caloyNovember 26, 2014 at 2:34 am
Try this changes: connect directly the TH to 12v from the relay, connect it to the output terminal of the VR which is the other terminals of the VR one is connected directly to +12v from the relay and the other connected to GND. And for the trigger terminal of ic555 use 33ohm 1/4w resistor connect to GND. Adjust the VR until you can reach the voltage of 13.8v. Hope it can help.

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[email protected]’SharojalhasanAugust 7, 2014 at 12:31 pm
Hlw can i use 3Ahm transfermer

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[email protected]’SlyderAugust 29, 2014 at 9:38 pm
Hi
I would like to know the formula for calculate the voltage that I want to start charging the battery.
At pin 2, the voltage is around 2.5 volt and the pot can change this value so, what voltage I must
have if I want to start charging at 11.5 volt for example. There is probably a formula to calculate this,
I would like to know this formula.

Thanks to share

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[email protected]’Hassan RazaSeptember 8, 2014 at 9:20 pm
Hi sir!

What changes should be made to controll an Input current of 7-10 Amp and 18 volts PV. Basicaly i have Solar panel of 150 Watts. Waiting for your reply

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[email protected]’mathewSeptember 15, 2014 at 5:37 am
is there a pdf version of the datasheet?

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[email protected]’RUTVIKSeptember 15, 2014 at 11:35 am
HI,
SIR, IT IS AUTO OFF BATTERY CHARGER IT’S OK BUT IT IS AUTO ON ALSO?
ANSWER ME FAST I AM WAITING FOR YOUR ANS ……

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[email protected]’iyiola semiuSeptember 26, 2014 at 9:46 am
Sir how many amp and voltage can be use to charge 12vby200ah b3.

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[email protected]’jagadeeshpatil0September 29, 2014 at 4:50 pm
What about float charge no mention of float charge. Please provide details of fast charge and also float charge.

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[email protected]’EmmanOctober 12, 2014 at 7:06 am
hi sir,

i ask if the pin 7 of the 555 IC is connected to the other pin of Relay (the one that has no connection)???

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[email protected]’iyiola semiuOctober 13, 2014 at 9:36 pm
Sir please how can I add LM393 IC to circuit to work as power surg,tnx.

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[email protected]’ainsworth lynchNovember 9, 2014 at 2:26 am
If I use a 12-0-12 transformer would that be ok? I only see 15v on the step down side of your transformer

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[email protected]’ChikeNovember 22, 2014 at 4:21 am
Hi sir,I have read all d coments bt u didn’t reply them dat has d problem of both leds coming up while d voltage refuses to vary.pls correct it for us I face d same problem.

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[email protected]’caloyNovember 26, 2014 at 2:45 am
in this circuit you can expect that the red LED will always glow bcause it is connected direcly from the transformers DC outputs. Only the green LED will do the on and off during charging. During charge mode green LED glow and when fuylly charge greenLED turns off. Try this changes: connect directly the TH to 12v from the relay, connect it to the output terminal of the VR which is the other terminals of the VR one is connected directly to +12v from the relay and the other connected to GND. And for the trigger terminal of ic555 use 33ohm 1/4w resistor connect to GND. Adjust the VR until you can reach the voltage of 13.8v. Hope it can help.

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[email protected]’xian leeJuly 31, 2015 at 3:55 pm
good day sir. I want to ask can I use 1k variable resistor on this circuit f not which part affected and need to replace, I ask this because in my area barely hard to find electronic items like this. that’s why I need replacement only

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[email protected]’giotestDecember 7, 2014 at 12:24 pm
can i skip the 2x 5 Ohm 10w residtors ????

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[email protected]’giotestDecember 7, 2014 at 12:30 pm
6A4 Diode??? can i use 1N4006 ,1N4007,1N4001 ???

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[email protected]’john l.December 11, 2014 at 10:03 pm
what are the 10E 10w resistors??? (Ohms)

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[email protected]’Ricardo VersianiJanuary 14, 2015 at 8:37 pm
You have 230 VAC input in my case i have 110VAC. WOuld this circuit still work for me the way it is or would i have to change some components?

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[email protected]’AjithJanuary 16, 2015 at 11:10 am
How to set the preset voltage.,so that i can stop the adjustment

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[email protected]’alieJanuary 17, 2015 at 12:15 am
how to calculate output current?
i need a formula..

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[email protected]’saif ur RehmanJanuary 29, 2015 at 6:55 am
sir i want circuit that automatically on when the goes and auto off when the light comes..???

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[email protected]’AsanthaFebruary 6, 2015 at 3:03 pm
sir . what is a 10E 10w (resistor oms / k ) plese help

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[email protected]’DjeffFebruary 10, 2015 at 11:51 am
10E 10W mean 10 Ohms 10W resistor

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[email protected]’KishorFebruary 18, 2015 at 9:41 am
We need12 volt 4.5 ah battery charger
Auto cut off
Pls send me quatation

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[email protected]’TalhaFebruary 18, 2015 at 3:46 pm
hi! sir did all the resistors are of 10W?

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[email protected]’Salim MiahFebruary 25, 2015 at 3:40 am
Hi,
It posible relay use to cut ac. I mean this ckt cut battery positive terminal, but I think cut ac power supply by using relay tx primary side.

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[email protected]’bhasiMarch 2, 2015 at 4:02 am
I made the circuit bu my green LED always ON..and no auto cutoff at 13.8V

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[email protected]’Rishi RajMarch 31, 2015 at 7:25 am
Hi,
This circuit will be applicable for 12 volt 30 AH Battery (Auto battery) ?

I have 5 Amp Transformer, Can I use this circuit ?

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[email protected]’xander gelicameMarch 31, 2015 at 12:22 pm
hi sir my trans4mer is 15-0-15 v then i put the 6A4 diode at 0-15 v and i filter with 4700uF /25v cap. then i put 1 more 6A4 diode at + but when i test it the output voltage is 22.3v. and the 10E 10w resistor is very hot and also my ic555..

plzz help me..

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[email protected]’biniApril 3, 2015 at 3:15 am
your trans is not 15-0-15..might be 18-0-18..test with a multimeter

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[email protected]’xander gelicameApril 3, 2015 at 12:54 pm
yes its 18-0-18 ..but how can i make it 12v bini?

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[email protected]’biniApril 10, 2015 at 1:28 am
use lm317 0r lm7815 to make it apt for 555 voltage level..its a simple circuit and cheap components

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[email protected]’xander gelicameApril 11, 2015 at 9:35 am
thank you bini..

[email protected]’RoniJune 5, 2015 at 1:40 pm
Please can you give me the link of ckt diagram of 18-0-18 to 15-0-15 used by lm7815?

[email protected]’ANAND KUMARApril 8, 2015 at 12:20 pm
DEAR SIR, PLEASE HELP ME ABOUT THIS CIRCUIT AND HOW IS WORK COMPONENT IN THIS WORK.

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[email protected]’Rishi RajApril 9, 2015 at 5:28 am
Hi,
My transformer is 4 Amp, 12-0-12 Volts, Can I use this circuit for charging ?

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[email protected]’biniApril 13, 2015 at 5:04 am
Ya..but battery won’t charge beyond 13v max.

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[email protected]’Adnan TayyabApril 18, 2015 at 10:58 am
Sir I made it as given above schematics on PBC, I have some problems please help me.
I am using 15-0-15 transformer (2A). I got only 5V on pin number 4 of 555, 5.2 on pin # 3 of 555 and 4.9 at the input of relay. means 12v DC relay not operate on that voltage. kindly reply me what i do and how to solve this problem???

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[email protected]’harishApril 21, 2015 at 6:56 am
hai sir, evething is 5n….how i can made the pcb. As per schematic /comments u given the changes know…….pls let me know design is over, i need to make a pcb pls confirm it sir. Which type of relay i wnt to buy i have little bit confusion if u have the image means pls send me sir with connection……..i am awaiting ur reply

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[email protected]’EugeneMay 4, 2015 at 6:16 am
Thanks for this. A couple of questions though.
My reference voltage on pin 5 is reading 18.2V and my 12V battery is obviously overcharging. Supply is 15V 3A. Across the zener it’s reading 5.1V. Any idea on what could be wrong?
Also when the battery has a very low voltage or is not connected the relay oscillates. Any advice on how to disable the circuit in this situation?

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[email protected]’suraj chauhanMay 6, 2015 at 5:46 am
I am suraj.I have 13 volt transformer can I use this

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[email protected]’Sarfaraz …