# ACPI Battery last full capacity

## foxcub

I've been using APM happily for a long time, and never looked at any readings in any detail. Today I have decided to switch to ACPI in the hope of improving the battery life of my laptop. It's gotten to be really bad. After the switch, I looked at /proc/acpi/battery/BAT0/info, where there were two disturbing lines:

```
design capacity:         47520 mWh

last full capacity:      19820 mWh
```

What was even scarier was that after I discharged the battery and then charged it again, the last full capacity line became 19800 mWh. Is this really normal (it's less than 50% of the design capacity), and decreasing right before my eyes? Is there anything I can do to restore it?

The laptop is about 1.5-2 years old.

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## Taladar

Every laptop battery is different. Perhaps you should post the Laptop model and (if you know it) the battery type (ni-cad or li-ion,...).

How long can you use the laptop with battery? Is that time only 40% of the time it was when the laptop was new?

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## foxcub

The laptop is Thinkpad T41 (2373-4HU). The battery is Li Ion (OEM: Sanyo). I never really measured the times that I could use the battery when the laptop was new (plus I don't use battery that often), but it's definitely considerably shorter than it used to be. 50% seems like a reasonable guess. 

I somehow have a feeling like it stops charging before its physical capacity is up (which makes me hope that it's a software problem), but perhaps I'm just kidding myself.

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## crdlb

Sadly, that may be normal.  Batteries, especially when not properly cared for, lose capacity over time.  My Thinkpad T42's extra capacity battery reports this after just three quarters of a year:

```
design capacity:         71280 mWh

last full capacity:      48590 mWh
```

   By proper care, I mean discharging the battery to 40% for long-term storage, removing the battery or the power plug when its charge nears 100%, charging it as much as possible while the laptop is off or sleeping, etc.  I wasn't able to do things like that until recently because I couldn't get sleep to work (mis-configured kernel) or hibernation (not enough swap).

Your case does seem a little extreme, but not entirely out of the ordinary.

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## foxcub

Thanks for the info, crdlb. I didn't do the first two of your suggestions, but certainly did the last one (most of my battery use really came from when I was moving the laptop from one place to another (home to work), and the laptop was sleeping. Occasionally, I would also leave it sleeping over night unplugged.

Out of curiosity does it make a difference whether one is using APM or ACPI on how much the battery deteriorates? Until today I have been using APM.

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## Schwinni

 *foxcub wrote:*   

> Out of curiosity does it make a difference whether one is using APM or ACPI on how much the battery deteriorates? Until today I have been using APM.

 

No, that shouldn't matter.

That your last full capacity is much less than the design capacity shows that your battery is broken, or at least some cells are.

Perhaps you can get some help in a newsgroup like "sci.electronics.repair".

Or have a look at http://sweb.cz/Frantisek.Rysanek/battery.html.

Greetz,

Schwinni

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## hw-tph

Laptop batteries generally get a *lot* worse with time. Here is the info from my 12 months old HP nx9105 battery (same as Compaq R3000 series):

```
hw@devon:~$ cat /proc/acpi/battery/BAT1/info 

present:                 yes

design capacity:         4400 mAh

last full capacity:      1627 mAh

battery technology:      rechargeable

design voltage:          14800 mV

design capacity warning: 220 mAh

design capacity low:     132 mAh

capacity granularity 1:  264 mAh

capacity granularity 2:  3780 mAh

model number:            Primary 

serial number:           

battery type:            Lion
```

This is an 8 cell Li ion battery that has been used daily for exactly one year. I'm looking to upgrade to a 12 cell replacement battery as soon as I can afford it.

Håkan

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## foxcub

Thanks for the info. One more semi-related questions. There are plenty of batteries being sold on eBay (that are listed as Brand New), that are considerably cheaper than their equivalents from IBM. Is it the same quality as what IBM sells? Is there anything I should watch out for?

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## Schwinni

 *hw-tph wrote:*   

> Laptop batteries generally get a *lot* worse with time. Here is the info from my 12 months old HP nx9105 battery (same as Compaq R3000 series):
> 
> ```
> hw@devon:~$ cat /proc/acpi/battery/BAT1/info 
> 
> ...

 

Your batter is really broken.

Here is my info (Acer TM291LCi, for 2 years now in daily use);

```

present:                 yes

design capacity:         4000 mAh

last full capacity:      4000 mAh

battery technology:      rechargeable

design voltage:          14800 mV

design capacity warning: 420 mAh

design capacity low:     156 mAh

capacity granularity 1:  264 mAh

capacity granularity 2:  3780 mAh

model number:            PA3206U

serial number:           1658Q

battery type:            Li-Ion

OEM info:                COMPAL

```

Greetz,

Schwinni

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## necromncr

Dont forget to see this.

Spoiler: dont flash your bios!

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## bonbons

 *Schwinni wrote:*   

> Your batter is really broken.
> 
> Here is my info (Acer TM291LCi, for 2 years now in daily use);
> 
> ```
> ...

 That's looking quite a lot too good... probably your battery information is not fetched correctly... what does the current status tell when the battery is full or has been used for some time?

Anyhow, way too often batteries are poor quality, they tell, can work for up to 1000 recharges, but most batteries are more or less dead long before 500.

Li-ION batteries seem to stay top-fit for a longer time than Ni-MH oder Ni-Ca batteries (they don't have the memory-effect, or lazy-battery effect of those), but when they start getting ill, they get really ill. My laptop battery "lost" 50% of it's original capacity durin a period of reduced use. In addition to having lost that much capacity, the behavior was very anoying, battery monitor told state going from 100% down to around 50%, and suddenly it dropped to 0.

Mobile phone batteries are no better, the work fine, and suddleny the phone just powers down after a few seconds of communication, but have no problem with standby.

Looks like the Li-ION lose their strength for heavy load when they get ill. I would not be surprised that they could provide most of their capacity at low current, but just fail over if current is higher. (even currents they managed with ease in their yougth)

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## Schwinni

 *bonbons wrote:*   

> That's looking quite a lot too good... probably your battery information is not fetched correctly... what does the current status tell when the battery is full or has been used for some time?

 

"/proc/acpi/battery/BAT1/state" tells me 4000mAh when it's fully charged, so there shouldn't be a problem.

My notebook still runs a few hours.

Greetz,

Schwinni

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## Earthwings

 *foxcub wrote:*   

> The laptop is Thinkpad T41 (2373-4HU). The battery is Li Ion (OEM: Sanyo).

 

I've got a T41 2372-1FG and a Sanyo LION battery as well.

 *grep capacity: /proc/acpi/battery/BAT0/info wrote:*   

> 
> 
> design capacity:         47520 mWh
> 
> last full capacity:      25220 mWh

 

I talked to other Thinkpad owners (R-series) and the last full capacity does look similar there. My laptop is ~20 months old btw.

 *Quote:*   

> I somehow have a feeling like it stops charging before its physical capacity is up (which makes me hope that it's a software problem), but perhaps I'm just kidding myself.

 

It's normal, batteries will die after some time.

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## foxcub

Got you, Earthwings. Thanks.

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## bonbons

 *Earthwings wrote:*   

> It's normal, batteries will die after some time.

 Yes, it's normal, but the promisses battery manufacturers make are far too optimistic (e.g. rechargable up to 1000 time for standard R6 & Co batteries)

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## d0ne

hi

does anybody knows some linux software to work with the battery? like reseting and stuff?

thx

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