Laptop Battery Lifetime


What’s up with my battery? I got this laptop, a Lenovo T400, about a year ago, and my 4 cell battery is reporting 37.4% capacity. This sucks. I’m going to need to get a new one.

eitan@sparky:~$ cat /proc/acpi/battery/BAT0/info
present: yes
design capacity: 37440 mWh
last full capacity: 14010 mWh
battery technology: rechargeable
design voltage: 14400 mV
design capacity warning: 700 mWh
design capacity low: 200 mWh
capacity granularity 1: 1 mWh
capacity granularity 2: 1 mWh
model number: 42T4573
serial number: 2242
battery type: LION
OEM info: SONY

What did I do to deserve this? Any fellow Internet users know? I have been running alpha versions of Ubuntu often, has there been some major power management bug that may have killed my battery? Have my usage habits been destructive? I can’t think of any awful abuse that I put my battery through.

Laptop Battery Lifetime

12 thoughts on “Laptop Battery Lifetime

  1. I have a similar problem with my T60 – only 70% capacity after half a year. I think the problem is leaving the battery inside the laptop all the time. I guess ubuntu/linux does not stop charging the battery when its full or probably it is just because of the heat…

  2. frej soya says:

    See if you can get the number of recharge cycles… and check with whatever lenovo says. I believe apple gives a max recharge cycles if it’s going to be replaced.

    But yes, every cycle lowers capacity so plug in when you can.

  3. Pierce says:

    All gadgets with lithium ion batteries tell you to just plug it in whenever you want, there’s no need to fully discharge and recharge, in fact that’s harmful.

    However my experience has been the opposite.

    My current laptop (over a year old) has 5289 mAh / 5800 mAh (why amps and not watts, I don’t know, but I can confirm that it still has most of its original battery life, which was around 5 hours). I let it drain all the way and recharge it fully at least once a month, but sometimes I end up draining it once a day.

    On the other hand, back when I worked at a computer repair shop, I saw some laptops which were put in a kitchen and plugged in and never moved, and a year later when someone tried to use them unplugged they only lasted 30 minutes.

    I had a palm with lion batteries many years ago which I treated as suggested, docking it every time I returned home, and the batteries became useless in a matter of months (which started me on my current battery treatment habit).

    Now I also let my phone drain before recharging it, which seems to work ok. Maybe my phone would be fine if I just let it charge everytime I got back to my apartment, I don’t exactly have the equipment or motivation to run a proper experiment. People still tell me I’m crazy, that’s not how lion batteries work… maybe I am.

  4. Sven says:

    There are some good tips at

    A common problem is that people use their notebook a lot with AC connected and when they run it on battery, then they do that for a short time only. Unfortunately the default battery charge logic aims to keep your battery fully charged and will start charging a battery that is only a few percent discharged as soon as you plug your notebook in again. This quickly wears out your battery.

    If you get a new battery, make sure you adjust the battery charger thresholds as described at

  5. Soroush says:

    I have been using Ubuntu for a year with this laptop. But after installing karmic alpha, the battery capacity dropped from 80% first to 49% and then to 39%.

  6. Paul Johnson says:

    I got a T400 around the same time you did, Lenovo replaced mine no questions asked (though I did it the very last day my battery was still under warranty).

  7. Bear in mind that to get the tp_smapi stuff in Karmic you’ll need to use module-assistant to build the tp_smapi source package for each new kernel you install.

  8. Astron says:

    Some advice:
    * Try to keep your battery between 20 and 80 % charge most of the time (better is 40 – 60 %) — below is harmful, above is less harmful
    * When the computer runs on AC, remove the battery (I guess it is better not to remove the battery while the computer is running), also see above.
    * every 30 (or more) cycles “reset” the battery by charging completely, then discharging almost completely twice

    I’m having a hard time trying to follow this, too.

  9. Ara says:

    Similar thing for me:

    ara@sushirider:~$ cat /proc/acpi/battery/BAT0/info
    present: yes
    design capacity: 56160 mWh
    last full capacity: 36550 mWh
    battery technology: rechargeable
    design voltage: 10800 mV
    design capacity warning: 1827 mWh
    design capacity low: 200 mWh
    capacity granularity 1: 1 mWh
    capacity granularity 2: 1 mWh
    model number: 42T5262
    serial number: 27919
    battery type: LION
    OEM info: SANYO

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