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 » Reviving Laptop batteries :

Reviving Laptop batteries
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Here is a way to revive your old battery pack. Usually the laptop battery is the first part to break. On older laptops a new battery pack can cost more than the PC itself, so buying a new one is no option.

I have had different results with different battery packs, but the usual is a 50-70 % increase in time running on batteries. My personal experience is that NiMh batteries are much easer to rejuvenate than LiIon.

There are no guarantees and you might end up destroying your Battery pack. It might even explode, so continue at your own risk.

Step 1 - Drain the battery

Remove the AC adapter and let it run until the battery is completly empty. You can turn off all power saving features to speed things up. When it goes in to sleep mode, try to turn it on until you get no response at all.

Step 2 - Drain the battery even more

Using a low wattage 12v lamp (car brake light for example), you can empty the battery pack even further. Check the voltage of your battery pack, and use a lamp with a suitable voltage. Remember not to use a lamp with too high wattage as this could damage your batteries.  Also, be careful not to short circuit. You will need to figure out where the ground and + voltage is. On this IBM thinkpad batterypack they are located on the opposite corners in the connector.

Connecting to battery using paper clips

Paperclips are ideal to connect the lamp to the battery connector.

Let the lamp shine until you see it going slightly dimmer. It is important not to drain it too much (especially Li-Ion).

Draining battery using lamp

 If you are the cautious type, you can hook up a multimeter and measure the voltage. I usually don’t like to bother, but you can calculate how much you can drain (Skip if if you don´t care that much):

For example if your battery has 9,6 Volts printed on it:

9,6 / 1,2 = 8 cells

8 x 0,6 = 4,8 V.

So, it’s safe to drain this 9,6 V pack to 4,8 V.

Step 3 - Recharge

Now it’s time for the for the fun part. I like to log just about everything to track the results. If you like that too, just download and run apmmowin before inserting the battery. The output can be redirected to a file like this:

apmmowin > cycle1.txt

Recharge to 100%, and repeat from Step 1.



For this article i have used apmmowin to log the results. The graph below shows the increase in battery time from 50 minutes to 2 hours and 41 minutes:

Battery graph

These results are from four cycles with a  IBM Thinkpad R40 9.6 V Ni-Mh battery pack.

Before the discharge / Recharge cycles the battery time fell drastically from 60% to 10%. Afterwards the drop has dissapeared and the discharge rate is much more constant.

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27 comments to “Reviving Laptop batteries”

  1. Comment by karl:

    I think I rode something like this before, they use it I remember to rejuvenate the batteries on communication satellites, (they allso need those as their orbits make them pass through the shadow of the earth).

    great idea!

  2. Comment by Odaiba Net 18 « Hablamos de electrónica y tecnología:

    [...] Rejuvenecer baterias de laptops [...]

  3. Comment by Mark:

    It worked like a chram and I thank you!! I used it on an IBM also and it was my wifes; she thanks you even more than I do!! You can take this one for what you will but the end result is “IT WORKS”

    Thanks much

  4. Comment by Harry:

    Thanks for the nice post, however it is different from battery to battery how well it works. Some you just can’t revive while others get 80 % more battery time.

    Give my regards to your wife ;)

  5. Comment by Kenneth:

    Thx man. I got it in the fridge now :) hope it works

  6. Comment by Anton:

    Hi i was wondering if this would be ok to do on my powerbook g4’s LiIon battery, i read on some post that draining this type of battery would cause a permanent damage as to not be able to recharge past that low point.

  7. Comment by mr2000jp:

    i know that this is good for the ni-mh and older batteries , but the li-ion batteries doesnt get better this way ,

  8. Comment by hooyator:

    Vsem sasat koni!

  9. Comment by Mario:

    would this work if my battery has a 10 min charge?

  10. Comment by brasays:

    merci bcp mon ami

  11. Comment by Chris Jones:

    I’m not sure that I believe this procedure. The calculations used 1.2V as the voltage per cell but with lithium batteries, it should be more like 3.6V per cell (but often they connect pairs of cells in parallel for more current). Lithium cells don’t like being deep discharged, so the only benefit I can see to this procedure might be if the software or electronics got some stupid idea about the state of the battery.

  12. Comment by aldar:

    dear sir/ thankfull for Explaine but need if can help me h have Panasonic toughbook CF-48 but have no battery & in my place in baghdad-iraq no Agent or any shop seal kind of this notbook …. i need the voltage uotput - Input for this battery mean diagram of PINs to make same battery by self ….if can help me be very thankfull ….


  13. Comment by donover:

    what is kenneth’s reference to the refrigerator about? Is there a refrigeration step?

  14. Comment by davee42:

    Someone told me that you can rejuvenate a laptop battery by putting it in a deep freeze overnight and then charging it up normally. I haven’t tried this yet myself. I have a Li-ion battery so it seems the deep discharge-recharge cycling will probably not work on it. Any comments on this deep freeze idea?

  15. Comment by Laptop Battery Revival Fail « Omi-kun:

    [...] me paint 4 hours at a time in Austin’s life drawing, so after I found a helpful article on getting some lost juice back from an old battery, I thought I would play around with [...]

  16. Comment by cheap computers:

    [...] This article is from [...]

  17. Comment by Gene:

    System reponded well. Thanks for sharin g this tip.

  18. Comment by Rob:

    Can anyone confirm this works on Li-ion batteries? Surely this is a bad idea as li-ions will be rendered useless if taken too low, and in a series pack without monitoring each cell individually during the discharge this is likely to happen.
    I can see this could help balance the pack, which could improve its overall capacity. If this is the case, i’d recommend discharging each cell individually, monitoring its voltage, not letting it drop below 2.5 volts per cell.
    This article appears to be written with NiMh batteries in mind, but don’t want to dissuade anyone who wants to experiment.
    Charging Li-ion batteries in a possibly damaged state or without a BMS (battery management system) CAN EASILY CAUSE A FIRE that also gives off very toxic gasses. So do it outside on a long lead with a powder fire extinguisher and the power switch to hand.

    From the guy who builds electric vehicles and who’s home recently burnt down.

  19. Comment by Mike:

    The freezer trick is for a battery that has an internal short due to metallic crystal growth that happens over time with charging. Eventually, you may get metallic crystals form a bridge between electrodes of a cell which turns it into a short circuit - doesn’t give power and doesn’t take a charge.

    By putting a battery in the freezer, it is HOPED that the physical contraction of differing materials will fracture these metallic bridges and allow the cell chemistry to operate again. If this doesn’t happen in the freezer, then I’ve heard you should try smacking the frozen battery pack against a hard surface so the shockwaves do the fracturing.

    With multiple cell battery packs, you can’t really tell the right thing to do - as each cell could have its own problems that require different treatment - so whatever you try should be done with care and low expectations.

    But, you will either (1) Be successful (to varying degrees) (2) Make no difference or (3) Make worse or TOTALLY kill your battery pack.

    The deep cycle technique (described by the OP) is quite good if applied to the right battery in an appropriate condition - but it’s no silver bullet and still requires a bit of care to do it right.

  20. Comment by samsung smx-f30 charger:

    to check my battery status via terminal and I googled around looking for a solution. I found the following website explaining in a pretty good way “How to check your battery status in Console”..Just like

  21. Comment by sb:

    Hi, at the risk of sounding dumb, how do you output the information from the soiftware

  22. Comment by oogabooga:

    As others have said, for Lithium batteries, the only way this could be helpful is for rebalancing the monitoring circuits. An interesting theory I heard recently, though, is that keeping lithium batteries cool makes them last longer. i.e. keep them in the fridge (NOT freezer) when not in use. You have to watch out for condensation of course (ideally in a vacuum sealed bag or something), but I’m giving it a shot with my camera and laptop spares. I’d be interested to hear others results too…

  23. Comment by jerryk:

    Here’s a refinement of this technique - I couldn’t find any 12V lightbulbs in my junkbox, so I made up a load
    of resistors in parallel. In series with this load, I put a string of forward biased silicon diodes - the same number of diodes as the # of cells in the battery. So, for my 8-cell battery, I put a string of 8 diodes in series with my resistors. The 8 diodes conduct until the voltage across them gets to less than .6V per diode - then
    the current through them falls off precipitously.

    The value of this arrangement is that the discharge doesn’t need to be babysat - just hook it up and come back later in the day! I used 10 470-ohm resistors in parallel, which gave me a discharge current of 190mA. When the battery voltage gets to 6V, the diodes just stop conducting.

    The resistors I used were 1/4W - If I was going to go buy resistors, I would have bought 1/2W - they get
    pretty hot. Hot enough to burn, ouch!

    A disadvantage of the diode string is that the current rate will fall off pretty fast as the batteries get close to the target voltage. If I was impatient, I’d want something that pulled full current until it got to that voltage,
    then suddenly shut off. And beeped!

  24. Comment by Charlie:

    i tried it on a dell studio 1737 and ended up totaling it…
    how to switch the battery on is not addressed in this article, so i tried ptting in the pc and having wires going out to the bulb, but it would only discharge to 8.50v (originally 11.1v, target was 5.55v) before the computer would switch it off. so i tried wireingit up, isolating the battery output from the computer with the bulb on the battery, and current still transferred through the existing wires and killed stuff (the light was definately dimmer here and blinked, going out for progressively longer periods till dead), tried a 9v battery on the laptop side to get it above 8.5v but it was loaded heavily.

    here says to GND the switching pin to turn it on ( ) but if all else fails, drill a hole in each side of battery, to discharge it, mine is an extra capacity type, the extra “foot” side of the battery i have is empty - but this is the negative side so socket can be used instead, with one hole on the other side..
    this has three cells in paralel, and three of those in series, nine total.
    finally tried to hard reset the battery hardware (disconnect GND) and it didnt recover (it has lights on the battery, these dont work at all now, before it gives a 10101 signal with the 5 leds now nothing)


  25. Comment by Charlie:

    battery model KM973, 85Wh pins: (written inside)
    P-,P-,AL,RES,PRS,DAT,CLK,P+,P+ (AL could be the switch? doesnt work now…) named: DELL PACINO
    probably could use these cells, reconditioned, with the new one…. mmmm 9+9 Cells… (or 9+6).

  26. Comment by Charlie:

    Dell pacino is the printed text on the PCB, i looked it up and got the circuit diagram of the entire computer (simular model). turns out, that SysPres is the pin that is connected to GND, (the pin i have called RES)

  27. Comment by » Tips for reviving laptop batteries o5 Recipes for Life:

    [...] it away and buy a new one without thinking about reviving the battery. The common belief is that reviving a laptop battery takes a lot of time and effort. But the truth of the matter is that reviving a battery is not that [...]