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Charging a Cellphone battery with a Laptop Battery

Last Updated on January 8, 2024 by Swagatam 5 Comments

The post presents a simple circuit that may be used for charging a cellphone battery with a laptop battery. The idea was requested by Mr. Gyashuddin.

Table of Contents
  • Recharging Cellphone Battery with Laptop Battery
  • Solving the Circuit Idea
  • Circuit Diagram

Recharging Cellphone Battery with Laptop Battery

hello sir my self md gyashuddin I want to know that it is passible to built a circuit which can ,recharge my cell phone battery from full charged my laptop battery.

If yes can you help me for this. I have : a laptop battery 10.8 V -- 48Wh(approx. 4444.4 mAh) and a mobile battery 3.7V -- 1450mAh In other word i want a adapter that recharge my cell battery from dc source ie my laptop battery my english is not good sir In simple word can i use my laptop battery as power backup for 3.7V cell phone battery Thanking you

Solving the Circuit Idea

Hello Mohammad, yes it's possible, just build a LM317 voltage regulator circuit, adjust its pot for getting 4.2V at the output, ........that's all...now you can connect the 10V to the input of the circuit and the 3.7V cell across the output of the circuit for fast charging it.

The detailed circuit regarding charging a cellphone battery with a laptop battery can be studied below:

Circuit Diagram

cell2Bphone2Bcharger2Bfrom2Blaotp2Bbatt 1

The value of R2 could be calculated either through this calculator software or using the following formula:

VO = VREF (1 + R2 / R1) + (IADJ × R2)

where VREF = 1.25

The IADJ  could be eliminated since it's too small to be considered in most cases.

LED Function

The shown LED will shut of when the 3.7V cell is almost fully charged.

Caution: Switch off the power to the 3.7V cell as soon as the red LED begins shutting off, in order to prevent the cell from over charging and damage.

For ensuring better safety you may want to set the output voltage to 3.9V, although this could mean the cell getting charged only upto 80% and not upto the optimal point.

For implementing an automatic cut-off you can try this automatic battery charger circuit concept

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  • 6.  6 Useful DC Cell phone Charger Circuits Explained

Filed Under: Battery Charger Circuits Tagged With: Battery, Cellphone, Charging, Laptop

About Swagatam

I am an electronics engineer and doing practical hands-on work from more than 15 years now. Building real circuits, testing them and also making PCB layouts by myself. I really love doing all these things like inventing something new, designing electronics and also helping other people like hobby guys who want to make their own cool circuits at home.

And that is the main reason why I started this website homemade-circuits.com, to share different types of circuit ideas..

If you are having any kind of doubt or question related to circuits then just write down your question in the comment box below, I am like always checking, so I guarantee I will reply you for sure!

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Reader Interactions

Comments

  1. ABBA says

    November 30, 2017 at 9:33 pm

    can 5v input be used for the regulator so that 1.25Vref and output be 4.85V.`thanks in advance

    Reply
    • Swagatam says

      November 30, 2017 at 10:02 pm

      The input has to be at least 6 to 7V, 5V might not work correctly.

      Reply
  2. Oyekunle Quadry (Gentlesoul) says

    January 31, 2016 at 6:15 pm

    can it be use to charge mobile phone directly sir?

    Reply
    • Swagatam says

      February 1, 2016 at 2:37 am

      yes it can be used….you can also employ the following deign for an auto cut off

      https://www.homemade-circuits.com/2012/02/how-to-build-automatic-6-volt-12-volt.html

      Reply
  3. Oyekunle Quadry (Gentlesoul) says

    January 31, 2016 at 6:14 pm

    great one

    Reply

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