How to charge and discharge laptop batteries to extend their lifetime

Michael PietroforteMVP By Michael Pietroforte - Wed, May 6, 2009 - 30 comments google+ icon

Michael Pietroforte is the founder and editor of 4sysops. He is a Microsoft Most Valuable Professional (MVP) with more than 30 years of experience in system administration.

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Laptop batteries

A laptop battery can be charged 300-1000 times. The actual number depends on the way it has been treated. In the last post of this series, I outlined the influence that the temperature has on a battery’s lifespan. Today, I will explain how a battery should be charged and discharged with care.

Fully discharge a new battery and then re-charge it. This calibrates the battery.

Calibrate the battery every 30 charges, i.e., fully discharge it and charge afterwards.

low-batteryAvoid frequent full discharges. In contrast to NiCd (Nickel-cadmium) and NiMh (Nickel-metal hydride) batteries, Li-ion (Lithium-ion) batteries show no memory effect. That is, it will do no harm to the battery if it is re-charged before it is empty. Full discharges will strain the battery.

low-battery-levelAvoid total discharges. Total discharges, i.e., to the cut-off point, can destroy battery cells. Not all cells in a laptop have the same voltage. Your laptop’s battery gauge only displays the state of the whole battery. If a cell goes below a certain voltage it will be destroyed. Therefore, it is safer to stop working when your battery level reaches 20%. The low battery level can be configured under Vista in the advanced power settings applet. Vista will warn you when the battery reaches the low battery level.

maximum-processor-stateAvoid high discharge rates. High discharge rates also strain the battery. Therefore, I would avoid power intensive tasks while working on battery. Some laptops come with special power management software that can disable unused components. Every piece of hardware that is active produces heat and wastes precious battery capacity. I also recommend checking out Vista’s advanced power management features. You will find many ways to reduce the power consumption. For example, I always set the maximum processor state to 1% while working on battery. You will be surprised at what a modern CPU can accomplish with 1% of its capacity.

Avoid full charges. Fully charged batteries deteriorate faster, especially at high temperatures. Monitor the battery icon in the systray and disable charging before it is fully charged. I guess this is not really a practical advice. Hence, it is only something for battery life-saver enthusiasts.

Dell-disabling-charging Avoid charging. This might sound like a rather unrealizable piece of advice because an empty battery has to be charged so it can be used again. The problem is that a lithium-ion battery only allows a limited number of discharge/charge cycles. If you are working on main, Windows will try to charge the battery whenever it falls below a certain level. This procedure is the worst thing that can happen to a battery. Usually, power management is set to high performance while the laptop is connected to AC. This increases the heat in the laptop while the batteries are being charged. One option is to disable charging while working on main. A far better option is to remove the battery if you don’t need it for the next couple of days.

In the next and final post in this series, I will give some tips on how a laptop battery should be stored to extend its lifetime.

Series NavigationHow to take care of your laptop battery to prolong its lifespan - How to store a laptop battery properly to save it from an early death

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30 Comments- Leave a Reply

  1. Aaron says:

    These are great posts on batteries – there’s some good info that I didn’t know, but you haven’t backed up this info with references. Looking forward to the next post.

  2. Thanks, Aaron. I’ve read quite a few articles about this topic lately. I will link to some in my next post.

  3. Adam Ruth says:

    Again, much appreciated. I haven’t delved too much into the Vista power management features, looks interesting.

  4. [...] A laptop battery can be charged 300-1000 times. The actual number depends on the way it has been treated. In the last post of this series, I outlined the. More here: 4sysops – How to charge and discharge laptop batteries to extend … [...]

  5. Soeren P says:

    “A far better option is to remove the battery if you don’t need it for the next couple of days.”

    But it’s nice to have the battery as a power backup when “someone else” trips and disconnects the power supply…

  6. Adam, many don’t know Vista’s power options. This is the place where you can get out most of your batteries.

    Soeren, I think your argument is mostly valid in countries with unreliable power supply

  7. RoninV says:

    I’ve tweaked some of my battery options, using the variables you’ve indicated, to see how things work out. Have a question about this, “Usually, power management is set to high performance while the laptop is connected to AC. This increases the heat in the laptop while the batteries are being charged. One option is to disable discharging while working on main.” According to this, the battery is discharging while connected to AC. “Disable discharging…” as in stop battery from discharging?

  8. Oops, sorry. I meant “disable charging”. I corrected it in the text. Some laptop power management tools have this feature.

  9. RoninV says:

    That’s what I thought, but I was thinking -Hey, to disable discharging would be great! There was a time when it was widely suggested that users should plug into AC whenever possible. In short, are you summarizing that batteries should be removed when the laptop is plugged into AC for an extended amount of time? Should users run their laptops on battery until the 20% warning before fully charging? Though charging can be disabled, the ability to configure charging of the battery to occur, only after its power as been reduced to that 20% remaining level, would be better.

  10. Yes, removing the batteries is the best way. I would run a laptop on battery only if it is necessary. That is, don’t wait until the 20% warning. The rule of thumb is to avoid charging and discharging whenever you can. There are exceptions though (calibration for example).

  11. RoninV says:

    If that is the rule, then users should “jack-in” to an AC whenever possible, but if you do run on battery, avoid full discharge. Not sure how one would keep track of a calibration every 30 charges, which is basically keeping track of how often one jacks-in to an AC with the battery installed.

  12. Yes, they should just disable charging when the battery is full. It might also make sense to unplug the laptop when it is off to prevent a battery that is almost full from being charged. The 30 charges are just an approximation. You can also calibrate the batteries once per month.

  13. [...] How to charge and discharge laptop batteries to extend their lifetime [...]

  14. Ha!Mi says:

    Hi, Is there a way to disable charging in vaio..???
    I couldn’t see anything about this option in control panel…!

  15. It is not necessarily in the Control Panel. Check out the programs that come with with your Vaio.

  16. Ha!Mi says:

    But there isn’t any CD program with my vaio, there is no cd with vaio at all…

  17. sam says:

    hi, i usually just plug the power chord whenever i use my laptop at home. is this safe?

  18. Ha!mi perhaps the software is already installed? You could also check the Sony website. It is also possible that Sony doesn’t offer such a tool. Then you can only remove the batteries when you don’t need them.

    sam, plugging the power cord is good for your batteries and it protects your laptop from power surges.

  19. sam says:

    thank you michael

  20. Rich says:

    I work away from home and office most of the time, usually at Wifi hotspots. Which of the following two methods are least damaging to the battery?

    1) Keep laptop plugged into AC outlook as much as possible with battery essentially always fully charged.

    or

    2) Don’t plug into outlet until battery discharges optimal amount, then plug in, then unplug, then plug in.

    Most hotspot users I see do not use the available AC outlets, while I always plug in as I assume method (1) is better.

    From what I read in this forum, the best method would be best to remove the battery most of the time while the laptop is plugged into an outlet and then occassionally reinstall the battery. This leads to another question:

    Is it ok to install the battery (and remove the battery) while the laptop is running and is plugged into an outlet?

    Thanks,

    Rich

  21. Ha!Mi says:

    excuse me for asking such a question in this topic…..
    how much electricity does a ;aptop use when the ac cable is plugged…??? (For example 500 watt)

  22. Ha!Mi says:

    Wow!!!!!!!
    any one know my question, ANSWER PLEASE…..

  23. Rich, I would go for 1) because charging will stop once the battery is full. I would then disable charging if your laptop supports it.

    Ha!Mi, This depends on the laptop model. Check your notebook’s manual or get power usage monitor.

  24. Simon says:

    Hi, fully discharging means running the battery down to 0%, right? (for the calibration process)

    And you said that full discharges strains the battery, but that is okay in the case for calibration purposes?

    And in the case that fully discharging means running the battery down to 0%, that will turn the laptop off in the process, and that is okay?

  25. 0% is difficult to achieve and probably not good for the battery. What I meant is to run the laptop to the point where Windows shuts down the computer automatically because of low battery. You will still have 1-2%. This doesn’t hurt the battery and calibration improves the longevity of the battery.

  26. Rakesh says:

    i have got myself a new lenovo z570. i am very particular about my stuff, and your site was the best guide i found on the internet, to take care of your laptop battery. i had removed the battery and stored it properly, but then i realised that i would need to take my laptop out once every week, needing the battery, and removing it again and again was not worth the effort. i always plug in my laptop when ever i use it and plug it out after my work is done, my battery charge generally hovers around 90-100%, after which it says that the laptop is plugged in, and not charging, is my habit healthy for my battery? kindly reply.

  27. Hazel says:

    Thank you so much for this!

  28. Hammershlag says:

    Another terribly written guide. Every guide I have read so far for laptop battery recalibration is poorly written and ambiguous.

    Please write a guide that is absolutely specific as to what one must do to recalibrate their batteries and charge and discharge correctly.

    The best measure to see if a set of instructions have been written well is simply note what the reactions from readers are like at. I’ve read through the comments, and many people are still asking questions about what to do, and still the answers to these questions from the author (if you can call him one) are ambiguous.

    It’s like the author is playing a game of how ambiguous he can be and how much confusion he can create. This goes for all the rest of the guides I have come across so far on proper battery management.

  29. Hammershlag, 4sysops is a site for IT pros and I think every IT pro can understand this guide. And what is ambiguous about “fully discharge”?

  30. el john says:

    as of now, only samsung laptops and netbooks have battery life extender features.

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