Laptop Maintainence

[stream303]

You just reminded me that I've got to clean my laptop running the SETI number cruncher!

The battery caveat listed earlier may be true, but newer batteries are "smart" and are supposed to protect themselves from this kind of premature death.

Mostly it is due to smart charging circuitry, which is critical for Lithiums not to be overcharged. However, you can run into premature death by extreme temps, always sitting at 100% charge, (even though they may be smartly trickle-charging) and extreme discharge by ignoring them for a long time.

I'd call Apple and get their official position on their particular batteries just to be certain though.

http://www.apple.com/batteries/notebooks.html

To the unwary, they might assume that their battery is only good for 300 charges or so if they read through it quickly and not realize that the spec is for when you do a full-discharge before recharge all the time. If you top them off after slight usage, they will last much longer - keeping in mind that they don't like to sit at 100% idling all the time.

They don't mention stockpiling spares. If you do have a spare, follow their guidelines and charge it to about 50% before storage, AND check on it every once in awhile to make sure it hasn't fully drained to the danger point of deep-discharge. Bettery yet, rotate the spare into service every so often. Even better would be to just buy a new one when you need it, as the chemistry is the freshest as long as you check the manufacturing date.

That battery page from Apple is probably the best one I've ever seen from a computer manufacturer.

[natrik]

Lithium Ion batteries, for example your laptop battery, can easily be damaged (reduced runtime, early end-of-life, etc) by routine use, especially if you're unaware of the following:

The LiIon chemistry doesn't like being kept at 100%, (and it really kills them to be topped off, like keeping them on A/C). I've had quite good results (cellphone batteries) storing them at 1 or 2 bars of battery (out of four). I've had bad results storing them at full charge. (NiCd and Lead Acid batteries LOVE to be kept at full or on a charger. I can't speak for NiMH.)

They don't like being HOT! They hotter they get, the more damage they can take on. The damage done is relative to the charge of the battery. The more power it has, the greater it harms itself in heat. Therefore keeping a charged cellphone or laptop battery in your hot car will kill it fast. (This is also true for NiMH and NiCd chemistry batteries.)

They don't like being IDLE. Storage in general will reduce the charge capacity of almost(?) any rechargable battery.

Here's some things I do to care for my expensive-to-replace laptop battery:
- give it action: I use Suspend mode (suspend to ram) frequently when I know I'll probably be back before the battery charge is gone.
- keep it cool: I have little feet (Cool Feet - see thinkgeek.com) to provide airspace underneath. Plus, in conjunction with a scrap of foamboard, my legs don't get rashes. ;-p
- keep it less than full charge: I plug in / unplug my system when it's going to be on AC for a while. It would be awesome to have a power applet to do the work and remember for me. I let it go down to 30%-60% (depending on when I remember to look) before recharging. 100% charge isn't too bad if you start using it right away, but I usually unplug close to 80%-90% just so I can turn it off at less than 100%. I try to leave it idle (laptop off for x days at a time) with 40%-60% charge.

My replacement battery (doing these things) is lasting much longer, and has more of a capacity per-charge than the two I inadvertently murdered.

Don't kill another battery!

Further reading:
- search for: lithium liion battery health tips
- wikipedia: http://en.wikipedia.org/wiki/Lithium_ion_battery

I know some posts say all this above mine, I just copied/pasted this from an email I just wrote yesterday.

-Nate

Edit: oh yeah, this is what killed the first one:

Keeping laptop on A/C with battery in, keeping a full charge whenever possible. Leaving it in my car trunk (heat). Keeping a spare (also dead now) at 100%, and hardly ever using it.

[natrik]

The following I found on a Gentoo forum:


Swappiness takes a value between 0 and 100 to change the balance between swapping applications and freeing cache. At 100, the kernel will always prefer to find inactive pages and swap them out; in other cases, whether a swapout occurs depends on how much application memory is in use and how poorly the cache is doing at finding and releasing inactive items.

The default swappiness is 60. A value of 0 gives something close to the old behavior where applications that wanted memory could shrink the cache to a tiny fraction of RAM. For laptops which would prefer to let their disk spin down, a value of 20 or less is recommended.

As a sysctl, the swappiness can be set at runtime with either of the following commands:
Code:
# sysctl -w vm.swappiness=30
# echo 30 >/proc/sys/vm/swappiness

The default when Gentoo boots can also be set in /etc/sysctl.conf:
Code:
# Control how much the kernel should favor swapping out applications (0-100)
vm.swappiness = 30


Some patchsets allow the kernel to auto-tune the swappiness level as it sees fit; they may not keep a user-set value.

Read the rest of the article. This is just a small piece of it.

-- Nate