12v Automatic Charger (Auto Cut OFF)




About: youtube.com/hawkarfariq

Intro: 12v Automatic Charger (Auto Cut OFF)

what is auto cut off battery charger?

some off charger maybe can't stop charging when the battery is fully charged.

Step 1: Circuit

so we want to show you a simple circuit for the charger when the battery is fully charged, the charging automatically stopping,

this is a circuit of the auto cut off battery charger, it has only:-

- one NPN transistor such as c1815 for controlling the charging,

- relay for cutting off this current path through the battery after fully charged,

- 10 kilo-ohm variable resistor connected to the base of the transistor,

the variable resistor used for restricting the voltage from how many volts you want to stop charging!

Step 2: Print

We prepared this circuit for you,

you can download it from the link below

12v Automatic Charger (Auto Cut OFF)

then print it by any printer,

and use any prototyping electronic circuit after that stick the paper to the board,

Step 3: Video

you can see this video and make step by step with this video



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12 Discussions


Question 26 days ago

LED diody sú zapojené opačne, ale inak je prístroj dobrý a trimrom mi idú nastaviť napätia asi 13,8 V - 15 V pri ktorom vypne a napätie pri ktorom zapne asi 10,9 V Požiadajte o informácie, ktoré treba zmeniť, aby bolo funkčné pre 6 V akumulátor. Ďakujem za odpoveď.


6 weeks ago

Buddy its working good but , Important Question ??? why you are not showing when you are reducing voltage <14.4v . The relay should reactivate when voltages goes <14.4 but its no reactive .


2 months ago

I wonder if battery reduce a value it starts automatically charging?


3 months ago

I made this twice and it didn't work. Has anyone made it and had it work hooked up to a charger?


3 months ago on Introduction

Many mistake on a simple circuit !

1- You have made a many mistake on a simple circuit. The pin's of the LEDs is reversed! Also, red and green LEDs connections to the relay are incorrect on diagram!

2- The first diagram of the film is one thing and the map you are printing is another thing!
3- Finally soldering is another thing! The circuit is wrong and not work. You distract everyone!
4- You've wiped out a very good HD movie. Why put the movie at a small point in the middle?
I ask you if you are really familiar with electronics, once again correct the diagram to show you respect public opinion. I can fix it, but I do not have a channel. It's best to modify it on the diagram below:

1) Modify the green and red LEDs in the connection with the relay.

2) Modify the positive and negative pin of the green and red LEDs that are reversed.

And... when you make a mistake, explain it to others and apologize. Many are here who are not professional and work based on your mistakes. That's not good. The more honest you are, the more visitors you have.
I apologize because I'm talking explicitly.


Question 6 months ago

Please help me understand how the LEDs will come on? I feel like the LEDs are installed backwards.


Question 8 months ago on Step 1

is it applicable to any kind of power source, eg. solar charger or alternator?


Question 8 months ago on Step 1

Ok. Porém os LED'S não estão invertidos no circuito?

Okay. But the LED's are not inverted in the circuit?


Question 8 months ago on Step 1

Как будет выглядеть схема на четырех выводной реле?

1 more answer

Answer 8 months ago

Что ты имел в виду? Я не понял?


8 months ago

It is very nice idea and good working circuit, but I am not very sure, if it is good for charging battery?.
There are 2 problems. The small one, Led diodes could not light. The big problem is voltage detected by transistor. It is not a battery voltage! (Battery voltage should be increased and should initiate cut off function.) If charger is using constant current, battery voltage is the same like battery, but after cut off, voltage of charger depends on its electric properties and could be different like battery voltage. In some cases can recycle charging.

1 reply

Reply 8 months ago

it's not bad for (10A - 15A ) charger but it's not very smart, known that if the charger connecting to the battery both battery and charger have the same voltage so its no problem if the transistor voltage gives from the charger. at first when you charge the battery the voltage path through the relay if a battery is fully charged not charging else charging it until fully charged.

if you want to make a smart charger you can use LM324 and regulate the voltage at 13.7v for large current and 14,4v for normal current.