Repair Dead Laptop Battery




About: A lover of nature, astronomy and cozy evenings in front of the wood stove.

We all know it. Suddenly, your laptop battery stops working. It won't charge and the moment you pull out the charger the laptop turns off. You have a dead battery. I have a fix that will revive it.

Please notice, that we are only reviving a dead battery. If you have a "bad" battery that only holds smaller charges for a few minutes worth of work, then this is not the right instructable for you. If your battery is completely dead then read on!
Oh, and by the way.. I cannot be held responsible for any problems you may run into, like damaged battery cells, fires, explosions and any other damage. Continue on your own risk.

People are suing like crazy these days, I have to say that. Anyway, next step!

Step 1: The Theory

A laptop battery typically consists of three battery pairs. Each pair is two battery cells soldered together in parallel. When you connect battery cells in parallel the voltage stays the same but you increase the capacity of the entire package (you can "pull more amps" out of them, more electrons).

Typically each battery cell (and thus pair) is 3.7 V. Now, when you connect them in series (be it individual cells or aforementioned pairs), you increase the voltage, thus getting 3. 7 x 3 = 11.1 V.

Too long, didn't read: each pack has to be 3.7 V.

Now, why isn't it charging? That's because one of the pairs does not have the same voltage as the others, making it impossible for the computer to charge them all at the same time.

Step 2: The Battleplan

We are going to open the laptop battery and examine each of the three "pairs". They need to have the same voltage. If not, we are going to recharge the pair with the low voltage back to 3.7 V.

Step 3: Tools

  • Multimeter (cheap and useful)
  • Charger, around 4-5 V

You may also need

  • Small cutter, to remove the paper on the battery.
  • Screwdriver to pop open the battery

Step 4: Remove the Battery

Unplug charger, turn over your laptop and locate the battery on the backside of the laptop.

It may have two buttons like mine. One is a lock, push it away from the battery. Now push the other button away and pull out the battery.

Step 5: Remove Paper

Now flip it over again. You will see a side with text. What you are looking at is a thick piece of special paper. We can safely peel that off with a small cutter or any sharp object. You really just need to start the peeling with the cutter and continue with your fingers.

Step 6: Pop Open the Lid

Now you are looking at this. That is actually a lid that is popped on.

You may need to use your screwdriver to put in the "crevice", turn it around and make it pop open that way. Once it has popped up, just remove it with your fingers as shown.

Step 7: Out Comes the Batteries

Gently lift the batteries from one end, then the other to make sure, that they are not sticking. Now turn it over and let the batteries fall out into your hand. Make sure that the circuit board also comes out together with the batteries.

Step 8: Seperate the Cells

Seperate the three pairs of cells just a bit so we can do some measuring on them. Also, get your multimeter.

As you can see, they are soldered together in pairs, so it doesn't matter where you put your multimeter tip. You will be measuring the voltage of the pair.

Step 9: Start Measuring

The voltage has to be 3.7 V. With that in mind, start measuring.

As you can see, the middle pair is bad here.

Step 10: Get Your Charger

Now we start the fixing process!

Get your charger. Determine which wire is the positive and which is the negative. Often there is a white or grey line on one of the wires. If not, just use a bit of tape. Now measure with your multimeter. If the voltage displayed is a positive number, then the red tip is touching the positive and the black tip the negative.
If the voltage displayed is negative, then it's the other way around.

Yes, I am measuring 11.9 V. That's because I didn't have a low voltage charger laying around, but if you do this, you may damage your cells. I didn't care a whole lot, though, and I haven't noticed any damage even though I've done this twice now.

Step 11: Help It Back to Life

Put your positive wire on the positive end of the battery and the negative on the negative. Recharge for a minute. Then wait 10-20 seconds before measuring. That is because the voltage in the cells will fall when you stop charging them. Here, I have already increased the voltage quite a bit.

When you think you have finally hit the correct voltage, wait half a minute and remeasure to make sure that it doesn't need a little more.

Step 12: Put It Back

Push the cells back together and put them down the battery cover as shown. Make sure, that the circuit board is all the way in (you can't do it wrong).

Put back the lid, it will pop in. Put back the sticker and if it doesn't stick (it really should), just use some transparent tape or glue.

Step 13: Back to Its Natural Habitat

Push it back in the laptop and push the lock into the locked position, which is towards the battery.

Step 14: Return of the Battery

Oh boy! Is it going to work (is anyone even doubting?!)?

Let it charge for one minute, then unplug it and try turning it on.

It is alive! I mean, of course it is.

Now let it recharge completely before using the laptop without the charger.

Step 15: Extra: If You Do Not Have a Charger Like Mine

Don't be discouraged! We'll just make one.

Grab your old 4-5 V charger, that you don't use anymore. Get a pair of electric pliers.

Cut off the plug. Seperate the wires (c'mon, you don't need instructions for that).

Now, grab one of the wires and close the pliers on them, but don't cut. Sort of pull away the insulation. You may need to use your fingers to pull it off completely. Twist the cable. Repeat for the other cable and you´re good to go!

Step 16: Final Words

That is how you fix your laptop battery for no money at all and in only half an hour! You may consider changing the cells, though, as dying this
way is an indicator of a bad cell. There are great instructables for that. But for now, just enjoy that you're awesome and could fix this yourself (and save some $50)! And who knows, maybe it will keep working forever?
Mine kept working for half a year before it needed a new treatment but hey, how else would one spend a Saturday evening, am I right?

Leave comments if you have questions or, well, comments!
Thanks for reading!

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    15 Discussions

    Vivek M S

    Question 8 weeks ago on Step 16

    I got to know what to do when my laptop battery is dead. Thanks a lot.
    But what If, my battery is leaked and badly smelling.???

    1 more answer
    ProtritonVivek M S

    Answer 8 weeks ago

    Now, I'm no professor in batteries but if I were you I would dispose of the cells. Maybe you can change the cells only. Like, buy new 18650 batteries and change them. There are good instructables for that.


    2 months ago

    Laptop batteries don't usually pop open as easily as that, and often you crack the plastic. I have a little bottle that I've had for years labelled Loctite Detach Glue Remover which softens the glue if you put it on and leave it a minute or two to work. I've no idea where you get it these days. Acetone might work, or at least ease the job a little, or if you can find another product containing heterocyclic ketone it'll be the same as mine. (Acetone is a ketone, but not a heterocyclic one, whatever that means.)

    3 replies

    Reply 2 months ago

    Explains the odor of a cell I accidentally punctured the seal. it had a bit of an acetone like scent. (and that battery is GONE!)


    Reply 2 months ago

    I didn't know such great thing existed, thanks for sharing. I did make some indentations in the plastic, but since the battery is in the laptop all the time, no one is going to see it.


    2 months ago

    There's also one more thing.... 18650 cells have an internal breaker that opens when the temp gets too high (usually off-gasses the battery as well.) this is where it gets dangerous unless you know exactly what you're doing.

    Notice on the "+" end of each cell, the point is surrounded by a paper gasket, with a little space of the O-shape of this, and the point. if you carefully press down around the gasket, You'll see the vents in the point. take a small, BLUNT point small enough to fit through the vent, and lift upward only slightly. remove the instrument, and check the cell for voltage. You might find it's at full voltage.

    the breaker opens when charging the cell, and it becomes too warm. You might also get some crystalized electrolyte that holds it open. the pressing down (when you lift up on the blunt instrument) pushes the breaker shut..

    Sounds simple, right? rememeber that I said Dangerous. for two reasons.

    #1, you can puncture the seal on the cell, and the electrolyte will leak when you start charging. the other danger, shorting the center point to the outer canister lip. LIion cells dump their full mAh amperage into a dead short. I had one cell burn a 17-AWG solid brass pin in half.(and my fingertip that was against it when it shorted.)

    2 replies

    Reply 2 months ago

    This is good to know, thanks for sharing!


    2 months ago

    Its a temporary fix and a good starting point . Lithium ion cells should be charged into their upper knees (4.2Volts) then all connected in parallel for 24 hours . This is called top balancing It should only need to be done once in a blue moon if the cells get out of balance.

    This is needed because each cell will now discharge with use down to its lower knee of (around 3.0 Volts) .So each cell will contain so much energy to release until one cell gets too low for the BMS and it will disconnect all of them.

    My suggestion would be to buy new cells and make up the pack again or buy a new battery complete. You can disconnect each cell and charge it separately on some chargers and thats what I do .

    3 replies

    Reply 2 months ago

    Thank you for this valuable information. Yes, it is temporary fix, that will help the battery go for another half year or, hopefully, more. I am planning to replace the faulty cells (or maybe the entire package) with some others I have in an old laptop I'm not using. The battery there is surprisingly good.


    Reply 2 months ago

    Looks awesome, thanks for sharing!


    2 months ago

    Every times,is the battery in the middle( the battery in external position about de laptop).

    I say "every time"because that is a commercial strategy.....

    six battery,same type,but only one have a lower quality....

    time after time(charge after charge....)this battery is detected by the BMS(battery management system) and the BMS (for precaution)switch off all component(a battery with problems of charge is like a resistor...resistor=hot,many hot.....bummm) you must buy another pack battery(or a new house)

    great battery work between 3.0volt and 4.0 volt but you can at 2.6/4.2 volt with a short life...

    charge must not exceded 4.2 volt....

    Other important,you must disconnected all wires before intervention because you can have 20 or 30 A in 0.2 sec during a short circuit(accidental)....directly on your body .....after work you can build again all connections batteries/BMS

    All laptob battery pack is in a hermetic enclosure from humidity,dust and a shock sensor is again the same battery pack is really hard....but you can conscientiously reuse all battery for a powerbank or others personal projects....

    this is only my opinion,(i open 30 or above battery pack)...i suggest to use caoutchouc gloves :) :)

    1 reply

    Reply 2 months ago

    I see, that's interesting. I'm glad the BMS is working that way; I would rather not buy a new house. :)