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.
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).
 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.
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Results
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:
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.
Friday, November 24th 2006 at 4:02 am
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!
Friday, December 1st 2006 at 6:08 pm
[…] Rejuvenecer baterias de laptops […]
Sunday, December 10th 2006 at 5:51 pm
Hey,
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
Mark
Friday, December 15th 2006 at 6:34 am
@Mark
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
Monday, January 29th 2007 at 9:56 am
Thx man. I got it in the fridge now
hope it works
Saturday, February 17th 2007 at 3:08 am
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.
Wednesday, March 28th 2007 at 6:30 am
i know that this is good for the ni-mh and older batteries , but the li-ion batteries doesnt get better this way ,
Monday, May 21st 2007 at 12:16 pm
Vsem sasat koni!
Wednesday, June 6th 2007 at 10:50 pm
would this work if my battery has a 10 min charge?
Monday, August 20th 2007 at 2:40 pm
[…] Rejuvenecer baterias de laptops […]
Sunday, December 16th 2007 at 7:28 pm
merci bcp mon ami
Wednesday, February 20th 2008 at 12:10 am
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.
Friday, April 18th 2008 at 5:23 pm
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 ….
aldar
Friday, April 25th 2008 at 2:50 pm
What a great tip! Another good use of the paper clip as a computer maintenance accessory.
Saturday, May 3rd 2008 at 9:33 pm
what is kenneth’s reference to the refrigerator about? Is there a refrigeration step?