Articles, Blog

DIY Laptop PowerBank (battery pack to charge your laptop on the go)

October 17, 2019


Owning a decent laptop is beneficial when it comes to productively spending your time on-the-go By for example working gaming or watching your favorite web video creator The only problem is the limited runtime of the laptop’s built-in battery pack which normally get charged up through the included laptop power supply which is fuced by main voltage so to charge slash power the laptop on-the-go I got the idea of creating a portable battery pack which we can charge up fully laptop power supply and later use it to give the laptop and additional runtime of around three hours The process of creating such laptop power bank with all the required voltage levels and safety features was not that simple though So sit back and enjoy my take on creating such a portable laptop battery pack Let’s get started This video is sponsored by JLC PCBs the most popular PCB prototype company in China which produces more than four hundred thousand square meters of PCBs per month So upload your gerber file today to try out their PCB service for only two dollars To start off I had to collect some data The built-in battery pack of my laptop stated a voltage rating of 11.1V DC and a capacity of 4400mAh So an energy of round 49 Wh The laptop itself states an input voltage of 19.5V with a maximum current draw of 6.15A which also correlates with the ratings of the laptop power supply To test this I plugged in at 5.5 by 2.5 mm DC jack into the laptop and connected it to a lab bench power supply sets to 19.5 V DC and sure enough the laptops battery pack started charging and while simultaneously running a benchmark it drew a maximum of close to 5A So 19.5V and a maximum of 6.15A should be the output characteristic of our laptop power bank. what is also important safety wise is how much the supply voltage fully laptop can vary Now since I did not feel like frying my laptop with over voltage I rather disconnected the power and started removing a few dozens of screws in order to find out how the DC Jack voltage is connected to the PCB ICs But even after removing the SSD as well as the cooling system I was not able to get to the DC Jack. What I was able to figure out though was that the input voltage is directly connected to this connector whose closest IC were this BQ737 and this TPS51211 The BQ737 is a one to four cell lithium battery charge controller which is obviously used to charge up the three s lithium ion laptop battery pack The IC features a maximum recommended voltage of 24V which gives us some space to play-rounds. But we should keep in mind that the datasheet also states that a voltage spike beyond the VCC voltage can destroy the IC Now the other I see here known as the TPS51211 is a stepped on controller for notebooks which creates a small voltage for the laptop components What a coincidence. This one even offers an input voltage of up to 28V so even more space to make mistakes with this knowledge we basically learns that 19.5V would be great but does not have to be spot on. Just like the power supply of the laptop does not exactly delivered this value So after reassembling my laptop which was only a bit tedious I tested whether it still work correctly which it did and grabbed my E-bike battery pack from a previous video. It consists of 13 lithium ion cells in series with two cells in parallel each. but feel free to watch the video about it in order to find out its specifications. How I built it and why I do not use it for my E-bike anymore and thus can we *propersite* it for those projects? The only problem is that thirteen cells in series is not only a bit too big but also comes with quite a high voltage as a solution I desoldered the thick + and – battery wires as well as all the balance wires and cut the battery pack at the eight cell series connection This way my new pack got the maximum voltage of 33.6V a nominal voltage of 28.8V and a minimum voltage of 20V at 2.5V per cell Also the pack can continuously deliver 40A and features a capacity of 5Ah which equals a nominal energy of 144Wh Thus by assuming a conversion efficiency of 70% we should be able to charge up the laptop battery pack up to two times which should give us three more hours of laptop runtime Awesome The next component for the power bank is this BMS circuit also known as battery management system This circuit adds an over current overcharge and over discharge protection to the battery pack as well as a cell of balancing feature which is pretty much mandatory for multi cell battery packs. So after soldering its included balance wires to the battery pack as well as new power wires and plugging in the connector We gotta predicted output voltage which is mandatory for the next components a powerful buck converter that can output up to 8A After hooking it up and flipping its power switch I adjusted its output voltage to 19.5V and sets its current limit to the highest value Through a DC terminal I then connected this output voltage to the laptop which as you can see charging laptops integrated battery just fine Even higher amp values are no problem for the set-up whose heat sink stayed pretty cool during all the tests and most importantly during switching on or off the buck converter it did not create any kind of voltage spikes which would be harmful for the laptop circuitry Next in order to check when the power bank is completely dry I also added a LED voltage tester to the battery pack for which I desoldered its buzzers hooked up a second pair of eight balance wires and connected them all to a male header to easily connect them to the LED power voltage tester. Now we can see the voltage of each cell and basically disconnect the battery at a cell voltage of 3V Last but not least we need to charge up the battery for which I got myself this powerful boost converter which can output up to 60V and 12A It is important though that it also features a constant current constant voltage mode To use it I firstly connected the output of the laptop power supply to the input of the boost converter and sets its output voltage to 33.6V which is eight times the recommended charging voltage or 4.2V After then turning the constant current potentiometer to its minimum value and “talking” up the boost converter output to the battery pack In series to my multimeter in current measuring modes I then adjusted the constant current limit to 2.5A which is two times the recommended charging current of one cell since we got two of them in parallel And as you can see by observing the rising voltage of the battery pack as well as the constant currents we are charging the battery properly with the CCCV charging methods to later easily check this charging process I also added a voltage / current monitor circuits to the output side of the boost converter. and after doing a couple of tests this set up seems to work surprisingly well So I created a suitable enclosure for the new battery pack as well as all the complementary components in one 3D design and 3D printed it afterwards. Once the 22 hour printing session was complete I combined the two parts of the enclosure and the lids with a bit of glue and moved on by mounting the switches and DC jacks and since I messed up when measuring the height of the LED voltage tester I had to shorten its PCB a bit before I could glue it into position Afterwards I use hot glue to secure the battery pack inside the enclosure did some cable managements and moved on by wiring all the DC jacks switches and buck converters to one another Of course explaining the wiring through words can be pretty confusing so if you plan to build something similar you can find a wiring scheme for these project as well as pictures and additional information As always in the video description. Now as soon as I secured the boost and buck converter to the enclosure with M3 screws I added the lid to the project created a connection wire for my laptop and did a final test by charging up the laptop power bank and afterwards using it to power my laptop which both worked flawlessly and with that being said I declare this project a success and I hope that you enjoyed watching this video If so don’t forget to Like Share and Subscribe Stay creative and I will see you next time.

7 Comments

  • Reply Steve Terry October 2, 2019 at 12:00 am

    Why endure all that charger loss? You'll almost certainly find in the laptop battery, banks of 3 Li-ion 18650 making 11V DC,
    open the pack and tap a couple of wires from the ends of the 3 cells, and wire to external banks of 3 x 18650 cells

  • Reply VV S October 5, 2019 at 8:07 am

    How much did it cost though it is a great project

  • Reply Kalyn Griffin October 6, 2019 at 7:38 am

    Anyone else notice how much the capacitors wiggled?

  • Reply DIY PINOY October 9, 2019 at 3:26 pm

    I wish i have a 3d printer 😢
    Unforunate i can only make powerbank of this version https://youtu.be/_L2Pi82GqtE

  • Reply Vathsal Hari October 12, 2019 at 5:07 pm

    dude can u tell me how much current can ur power bank can capable of discharging since i am also in need of making same one (mines acer predator input 19.1v 7amps) hence whether i should design a bank which should deliver voltage of 19v and current of 7amps….?

  • Reply Das Jucktmichnicht October 15, 2019 at 9:23 pm

    Man könnte doch die Powerbank mit viel geringerem OUTPUT Strom konzipieren und den Laptop nicht laden sondern nur den Betrieb damit gewährleisten bzw. die Entladung des Laptopakkus verzögern.
    Man kann dann Leistungsschwächere Komponenten nehmen.
    Optimal wäre eine Powerbank die man ansteckt wenn der Lappi-Akku voll ist und die gleichzeitig mit dem Laptopakku leer ist.

  • Reply hhkf ghkl October 17, 2019 at 1:51 pm

    Could you make a simple powerbank with only one usb type c connector whitch is an input and and output at the same time? I try to find any information how could I bulit one, but I can't find anything useful, please help.

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