Calibrate Laptop Battery

Category: Laptops

Sometimes my laptop's battery power meter shows that I have 10-20% remaining power, but it shuts down unexpectedly. Can I calibrate the battery so that the power meter shows an accurate measure?

Do I Need to Calibrate My Laptop Battery?

Laptop battery life is important to us road warriors. Can we squeeze in one more hour of work; finish watching this movie; complete a Skype phone call with a client; or receive that long-awaited email before we run out of juice? Most of us depend upon a battery life meter, either the one built into your laptop or an app that comes with a specific make and model of laptop. But those meters can mislead you.

"Calibration" in this context means ensuring that the software power meter accurately measures the amount of power remaining in the battery. Here's how the power meter gets out of synch with the battery over time:

The meter you see on your screen is a software app's representation of battery power level measurements taken by a specialized chip built into your computer. The chip measures the percentage of "fully charged" power remaining in the battery; assumes that "fully charged" means the rated capacity of the battery; and multiplies "percentage remaining" times "rated capacity" to come up with an estimate of how much power remains. But this simple math does not work in the real world.
Laptop Batteries

Most users recharge laptop batteries too little and too soon. They plug into an electrical outlet whenever one is available, even if the battery is still half-full or better. Then they unplug from the outlet before the battery is fully recharged. This "short cycling" does two undesirable things.

Recharging too soon can shorten the lifespan of a battery; it is designed to be recharged only so many times before being replaced. Recharging too soon means you are wasting part of a recharge cycle, and those cycles are not unlimited.

Unplugging from the electrical outlet before the battery is fully recharged may result in the battery "remembering" as its full charge a lower capacity than its rated fully-charged capacity. The battery stops recharging at that lower level.

The power measurement chip reports that the battery has more power than it truly does. Result: your battery dies before you expect it! It's as if your car's gas gauge reported 10 gallons when, in fact, only 5 gallons remained in the tank.

Some gas gauges translate gallons into miles remaining, and most laptop power meters translate watts into hours and minutes remaining. Time can seem to leap ahead when your power meter is not properly calibrated to your battery.

How to Calibrate Your Laptop Battery

Calibrating a laptop battery puts the power meter back into sync with the battery's actual "fully charged" state. It also helps the battery regain part of the power capacity it lost due to short-cycling, extending battery time. Most people should calibrate laptop batteries about once every two to three months. Here's how to calibrate your battery:

  1. Plug the computer into an electrical outlet and let the battery charge fully.
  2. Unplug the computer and use it normally until the battery is so drained that it goes into sleep mode automatically. (The battery really has a small reserve left, but if that is used up then data will be lost because the computer will shut down completely.)
  3. Repeat Step 1: Fully recharge the battery.

This process should also work for iPods, iPhones and other portable devices which have a battery life indicator on the screeen. Running the battery through this charge/discharge/recharge cycle should calibrate the battery and get it back in sync with the power meter display on your device.

There is some disagreement about whether this "deep discharge" should be done with Lithium-ion batteries. Apple recommends it for iPods, iPhones and other mobile devices they sell, but others claim that fully discharging a Lithium battery can damage it. I think the confusion comes from the fact that most devices will hibernate when the battery reaches a "critical level" of 5% remaining charge. So the battery isn't really "fully" discharged, but it's close enough to zero to make the calibration process work well enough.

Got something to say about calibrating a battery? Post your comment or question below...

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Most recent comments on "Calibrate Laptop Battery"

Posted by:

17 Aug 2010

Is this article for Lithium Ion batteries or the old Nicad/Nimh battery that has to be fully drained before being recharged. I thought the enemy of Lithium Ion battery was aging, not charging over and over. In other words, the battery will die weather it is used or not. Probably oxidation or something.

Posted by:

Albert Tan
18 Aug 2010

Would you recommend that we use our laptops connected to the power source all the time? Will this damage the battery or shorten its life?

Thank you

Albert Tan

Posted by:

18 Aug 2010

Hi Bob,

Useful article, but different battery chemistries require different charging strategies. Nickel-cadmium (NiCd) batteries became notorious for their "memory effect", which was caused by not fully discharging them before recharging. Eventually the battery became unable to work beyond the point at which it usually got recharged.

Modern batteries, such as Lithium-Ion or Lithium-Polymer batteries, don't have this problem and can be damaged by being completely exhausted. They are designed to be topped-up frequently, as you do with mobile phones and PDAs.

Useful info here:

EDITOR'S NOTE: I hear you, but Apple products use the Lithium ion batteries, and they still recommend periodically calibrating. See

Posted by:

20 Aug 2010

I thought the new batteries didn't have a 'memory' and therefore you could charge whenever you would like????

Posted by:

24 Aug 2010

I'm going to try your charge/recharge, to see if I can use my battery for more than 10-20 minutes, my question is: a few years ago they were talking about coming out with "specialized longer life batteries" that you would be able to purchase for you computer, can you tell me has that happened yet?

Posted by:

24 Oct 2010

Yes, Apple suggests PERIODIC recalibrating, but not constant full cycling which uses up Li-Ion and other types of batteries faster. HP's website also suggests an occasional full discharge for calibration.

Steve: These batteries don't have memory, but the digital "fuel gauge" can run out of sync over time and cause premature shut down.

Posted by:

01 Mar 2011

Finding a original batteries supplier? Check out You can get your batteries which available in several voltage. All batteries are guaranteed tested and original.

Posted by:

16 Nov 2011

I have the problem that the battery real capacity is like 44wh, and the reported capacity is like 700wh. I think that because of this, the battery is not charging at all, and when I unplug the power cord, the notebooks suddenly powers off. I can't recalibrate the battery because of this. Is there any way to alter the reported capacity other than recalibration? Thanks!!!

Posted by:

20 Feb 2012

My laptop doesn't go into sleep mode automatically, it turns off automatically when battery's dead. What should I do?

Posted by:

22 Jun 2012

In today's article (6/22/12) you stated that Lithium-ion batteries should be topped off and that deep discharge could be damaging. Yet, when I linked to THIS article you seem to say that deep discharge is necessary to calibrate the battery and that topping off a partially empty battery is a bad thing. Am I out of order to ask for clarification on this???

EDITOR'S NOTE: A good question, actually! See the note I added to the end of this article.

Posted by:

25 Feb 2013

I just bought a new battery and the problem I am having is the battery runs out of power while the laptop still thinks there is 18-20% remaining. The laptop just powers off, no hibernation or safe shutdown. When I plug it in and turn it on it still thinks the battery has 18-20% when in fact it is completely drained. I've let it charge up to 100% again and then unplugged it to use the battery and the same thing happens again... and again. I have alerts set for low battery and critical battery levels but it never reaches those levels before powering off. There must be a way to get this new battery to sync but I cannot figure it out.

Posted by:

21 Aug 2013

Thanks for the tip Bob!
I hope this will work.

Posted by:

22 Nov 2013

FYI I recently purchased a new Lithium Ion battery for a laptop of mine. I purchased a Ray-O-Vac brand from Batteries Plus. The instructions that came with the new battery....from the manufacturer....said to fully charge it.....then unplug the power supply and allow it to run down until the PC goes to sleep. Then plug it back in and fully charge it. This technique was recommended to sync the battery with the PC's monitoring function. I wouldn't think that the manufacturer would suggest a procedure that would damage the new, warrantied battery.

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