Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

First of all, I am not sure the title of this question is the most appropriate however this is what I meant to say,

There are many ways to extend the life of a laptop battery. One way is by not connecting it to the AC adapter all the time which will overcharge it. I read that in this website.

  1. Is there an application which automatically prevents the charging of the battery once it has reached 80% charged? I mean that is such a cool feature. Sometimes people tend to forget to remove the AC adapter and this could diminish the capacity and reduce the life time of the battery.

  2. Does the battery indicator in ubuntu display info or pop-up when the battery is almost dead (dead not in the sense of usage time) but rather a degraded battery?

share|improve this question
I read the opposite from that link. If you keep connecting and disconnecting the battery it will give you less life. Removing it will make you go through more discharge cycles. Check the graphics in your link. What is true is that keeping it at 80% or 50% of the maximum capacity will increase it's live. Note that you can to destroy a battery by letting it get to no charge at all (not where the computer reports 0%, but lower), check the storage instructions on your link. – Javier Rivera Jan 13 '11 at 15:02
up vote 16 down vote accepted

Wow, that web site is COMPLETELY WRONG. I am an engineer and among other things, sometimes design and build battery packs. I have read many data sheets from battery manufacturers and they all say the exact opposite, and I have experimental evidence that they are correct.

Batteries LIKE being fully charged. If the charger is overcharging them, then it is broken. A correct charger stops charging the battery when it is full, so it is good to leave it plugged in if you can. The more often you discharge the battery, and the deeper you do so shorten its life. A typical battery can handle several thousand cycles if you limit depth of discharge to 30% ( meaning you recharge it once it falls to 70% ). Going to 50% cuts the life of a typical battery down to the 1000 cycle range, and 30% or less drops it to a few hundred. A battery that is fully discharged and remains that way for weeks or months will loose much of its capacity if it can be recharged at all.

Notice the inverse relationship between depth of discharge and state of charge. Battery manufacturers and engineers use the former term. The marketing guy who wrote that web site probably did not understand the difference and so he got it upside down.

share|improve this answer
Wow thanks so much I never knew this, and was always getting wrong info from HP and others. – RolandiXor Sep 24 '11 at 2:25
great, i practiced full discharging policy and as a result my battery performance has degraded. – Ankit Oct 1 '12 at 13:18
Could you please provide some sources for your claims? I have always seen different information: the higher is the battery charge and temperature the faster the battery loses its capacity. See for example results of my quick search: Sony - Lithium Ion Rechargeable Batteries Technical Handbook - Long-term storage characteristics graphs on page 23, Lithium Ion Technical Manual - Cycle Life Characteristics - Effect of Charging Voltage. – pabouk Jan 27 '14 at 23:15
@pabouk, the second link you mention just says that overcharging the battery shortens its life, which is also well known, which is why you don't do that. At least every manufacturer spec sheet I have read on lead-acid batteries for 20 years has said that you want to store them fully charged, and top them off every once in a while. I have adopted the same practice for a laptop with lions I rarely use and in 5 years it hasn't lost any capacity. I'll see if I can dig up the long term storage specs from our supplier tomorrow, but even so, that's for when you aren't going to use it for months. – psusi Jan 28 '14 at 2:59
@psusi: excuse me for the delayed reply. In the second link the text is not only about over-charging: "Charging at a slightly lower voltage (4.10 - 4.15 V) will slightly reduce the capacity per cycle – but will increase cycle life because the cell is being stressed less." The full-charge voltage of 4.2 V was selected as a compromise between the capacity and life of the battery. When you cross certain voltage of the battery - the higher the voltage is the ageing of the battery is faster. – pabouk Feb 10 '14 at 21:55
  • You can get some additional information, apart from right clicking the battery icon next to the clock (get's shown when you pull out your power chord), by opening a Terminal and typing

    cat /proc/acpi/battery/BAT1/*
  • Does the battery indicator in ubuntu display info or pop-up when the battery is almost dead (dead not in the sense of usage time) but rather a degraded battery?

    Yes it does:

    alt text
    (something like that)

share|improve this answer
In case anybody's wondering: Yes this is an old screen shot, but I have actually seen this message — it's just hard to replicate. :) – Stefano Palazzo Jan 13 '11 at 23:24

I don't agree with the answer. Keep battery always 100% charged is NOT suggested.

For Li-Ion rechargeable battery (almost all laptop use li-Ion battery) , most manufacturers suggest to keep them in a cool and dry condition with 40%~50% capacity, no matter for camera battery or laptop battery. Why? Because this is the best conditon for battery storage. I have several evidences to support my opinion:

1) My Thinkpad X31 laptop with battery always full charged and dead in around 3 years later. Only 10% capacity left.

2) My Thinkpad T400 laptop has a battery with good condition after 3 years usage (more than 85% capacity left), by limitting the threshold to 30%~80%. I never overcharge or deep discharge the battery, it will reduce the lifespan of battery significantly.

3) I have several 18650 size Lion Sanyo batteries, which is the material of laptop battery, when they were shipped to me, the voltage are all around 3.78V (around 40% of it's capacity), while the full charged voltage is 4.20V. It means in factory, they are charged only to 40% capacity, for storage reason.

I saved them for around 2.5 years in refrigerator (so it's always cool), and the voltage of them still keeps around 3.76V~3.77V.

share|improve this answer

OMG, The top answer is wrong and it is very convincing since its first paragraph.

However, when it comes to "Batteries LIKE being fully charged", it is clear that there is some miXunderstanding between Li-ion and other batteries (Ni-based and lead-acid).

Ni-based and lead-acid car batteries "LIKE being fully charged" but Li-ion "DO NOT".

It is already correct that Li-ion LIKEs being in 30%-80% level of charge due to Li-ion cell deterioration beyond the range.

However, the answer were already right about depth of discharge i.e. the less discharge the more life cycle.

I used to have the same conclusion as the top answer when I first read that top search-result How to Prolong Lithium-based Batteries page and remembered only the part about depth of discharge. Years after I got to read it again and was so dazzled how could I missed to remember such critical part so I did search for Li-ion cell deterioration and found a research paper so I was certain it was true about 30-80% myth.

share|improve this answer
Welcome to AskUbuntu! Congratualtions on a good first answer! – cat Mar 21 at 12:45
Thanks. 5 more reputation so I can vote the above answer. – Grit Mar 22 at 17:35

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.