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# Charging a Laptop from a Car Battery

The following post explains a simple circuit which may be incorporated for charging a laptop while driving in car or some other vehicle. The circuit runs without incorporating an inverter or inductors in its configuration Let's learn more.

## Using Voltage Doubler without Inductor

The good thing about this circuit is that it does not  rely on an inductor topology for the required actions, making the design simpler, and yet effective.

As we all know a laptop runs using a DC potential from an in built Li-Ion battery just as our cell phones do.

Normally we utilize a AC DC adapter for charging a laptop battery in homes and offices, these adapters are actually SMPS power supplies rated with the required and matching specs of the laptop battery.

However the above power supply units work only with AC supplies, and in places where an AC outlet may be available. These units will not work in places where an AC source is not present such as in cars and other similar vehicles.

A novel little circuit presented here will allow a laptop battery to be charged even from a DC source such as a car or truck batteries (12V). It's a very simple, cheap, versatile and universal circuit which may be dimensioned for charging all types of laptops by adjusting the relevant components provided in the circuit. It's a simple plug and play charger circuit.

Normally most of the laptop adapters are rated at 19V/3.5Amps, however some may be rated at higher currents for facilitating fast charging.

### PWM Charging Control

The discussed circuit has a voltage adjustment features (via PWM) which may be suitably adjusted as per the required  specs.

The current may be suitably safeguarded by adding a 3 ohm 5 watt resistor at the output positive terminal.

As can be seen in the circuit diagram, the design is basically a powerful DC to DC voltage doubler circuit which utilizes a push pull mosfet stage for the required boosting of the voltage.

The circuit requires an oscillator stage for initiating the proposed operations which is configured around IC1a.

The components R11, R12, C5 along with the two diodes becomes a neat little PWM controller which sets the duty cycle of the entire circuit and can be used for adjusting the output voltage of the circuit.

Typically the circuit would generate around 22V from a 12V source, by adjusting R12 the output may be tailored to an exact 19V, which is the required laptop charging voltage.

SHARING IS CARING!

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

### 27 thoughts on “Charging a Laptop from a Car Battery”

1. yes R2 appears to be missing or differently numbered, I think R11 should have been R2…never mind the circuit is not affected anyway by this typo

2. I have tried to simulate this circuit on Proteus but it couldn't be able to simulate due to complexity in circuit ! Anyone one of you have tried this circuit in vero board if yes then I'll go for it as well

3. Great creativity comes from the minds of great people.

If you do not mind, I need some help.
I need a dc dc converter schematic for a project to install a PC in my car.
In other words, the ATX PSU 12VDC input.
If possible, Schematic and Part List.

• Thanks Zukarnai,

I could not correctly understand your requirement, are you referring to an inverter circuit that would allow 12V to 220V conversion, for operating your PC??

please clarify this, I'll try to provide an appropriate link for the same.

4. if the parts list is provided it would be very helpful.

• please click the diagram to enlarge, all the parts are indicated in the diagram itself.

5. Hi Swagatam

Here is modified Voltage Doubler circuit, the output is about 19V.

https://dl.dropboxusercontent.com/u/20969135/Voltage%20Doubler.gif

When a load (laptop) is applied the voltage drops to less than the input voltage.

Can you please explain why we could not get high current output when the original 13.5V battery source is directly connected to the diode D1?

• Hi Abu-Hafss

The voltage doubling is entirely the function of the capacitor reactances and input power sources.
Therefore if the load calls for relatively higher current would result in an instant drop over the excess voltage being achieved from the cap reactance and in turn will result in a voltage level just equal to the supply, in fact about 1.2V less if schottky diodes are not used.

6. Capacitor also functions as Storage device..if we use large value of Cap can't we replace battery with that ..

• you will require millions of microfarads, and spend thousands of rupees to make a 12V 7.5ah equivalent capacitor battery.

7. Hi am designing Charging control circuit for laptop using solar panel & 12V battery ..so can you briefly explain the curcuit you shared which may help my design..

8. Hi Swagatam

What are the functions of C3 and C4?
Isn't 100uF for C2 enough? C3 & C4 in parallel with C2 will just increase the capacitance by 200nF,

• Hi Abu-Hafss,

Smaller value capacitors quickly charge and discharge, so are better suited for high frequency disturbances, therefore all these caps have slightly different roles as far as filtration is concerned.

• No PCB layout for this, sorry.

9. Thanks!

I would suggest that you first build it over a veroboard or a breadboard and verify the circuit functioning, after this you can go for the final PCB designing.

10. I am facing problem in assembling this circuit… many of the ICs have 3 connection in the picture but actually there are 8…

I am so confused… Plz help…

• use only those pins which are used in the diagram, and leave the rest which are not used.

11. thanks for the circuit, but ic3 40106 is not available in our local market. Please help me

• you can try 7414 IC, but it will require 5v for operating so replace R1 with 7805 IC

12. thanks for the circuit… 😛

Maybe It will take some time to make it as i am confused with some symbols… :/

• you are welcome