how to preserve battery life span

[as_sass]

Hi!

simple question I guess for those who know something about batteries. Maybe someone has Thinkpad specific experience, too:

I purchased a new Thinkpad X60 tablet, and went for the 8 cell battery, plus an extra battery and battery charger. While it was important to me that I will be able to use the machine in battery mode, I will do so only occasionally, and use of the second battery will occur even more rarely.

Now my question:

How do I best preserve the batteries while not in use. Is it actually advisable to keep the battery in the machine while it is hooked up to the power cord (apart from the obvious "what if there is a blackout" thing)?

What should I do wih my spare battery.

a) leave it lying around uncharged
b) lave it lying around fully charged
c) have it permanently hoocked up to an external battery charger
d) charge and use from tie to time (and between use, either a or b)?

I figure that this probably has an impact on the life span of my battery, so I would greatly appreciate if any batery-savy person could share their wisdom with me!

Thanks!

as_sass

[Terrahawk]

Leave the spare battery in a cool place (the lower the temperature, the better but don't freeze it) with about 40% charge on it.

As for your main battery, you may as well just use it normally.

(see http://www.batteryuniversity.com for more tips)

[vincentfox]

If you do use it, try to avoid discharging below 50%. This appears to be what IBM counts as a battery-cycle. As I understand it the more times you deeply discharge it the short it's life. I got some batteries with X23 that were 2002 batteries but used for 50 cycles or less, and they still held a good 3 hours of charge.

[RealBlackStuff]

I put a new 4400mAH battery in my T23 on Sep-6-2006, and I've been using it regularly, but without fully discharging.
It still shows 0 cycles and holds for 3:20hrs.

[Deckard]

Since I mainly use my laptop on AC, I keep my battery in the refrigerator, charged at 80%. I check it once a month to see if everything is OK.

[Neil]

If you do use it, try to avoid discharging below 50%.

Is this how most of you folks use your batteries? I'm trying to get a handle on the best way to extend the life of my battery, and the directions on the Lenovo Tips and Hints page is not very clear on this. It says, "It is recommended that you deep-discharge your Ni-MH* battery every few months for optimum performance. Deep-discharge occurs when your ThinkPad system is used on battery power until the charge is at 0% (the system will automatically go into hibernation). At this point, attach the AC adapter and charge to 100%." Typically, that is how I've been using my battery. Fully charge it, take it out of the laptop, put it back in only when needed, use it, take it out. Use it that way until it become nearly fully discharged, then charge it up again.

Only thing, Lenovo says, "Do not deep-discharge Lithium Ion batteries." Of course Li-ion is what I'm using. So, what is the best way to use a Li-ion battery? They don't give any tips on that. Should I leave the battery in the laptop at all times? I leave the laptop connected to A/C all the time 24/7 until I need battery power. Will that overcharge the battery? Is it good to keep the battery charge to 100%, use it for a couple of hours a week, then reconnect to A/C before it gets down to 50%?

I'm just really unclear on how to get the longest life out of my rebuilt Thinkpad 770 Li-ion battery. A couple of years ago, I had a off brand compatible battery that only lasted about three months. Don't know if it was just a bad battery, or if I was misusing it, that caused it to die so young. I don't want that to happen again the my genuine IBM battery.

[Terrahawk]

Your battery won't overcharge. It will charge up to 100%, gradually self-discharge down to 95% and then charge back up to 100% again repeatedly.

Those figures may be different, depending on how you have set your charge thresholds. If you haven't set them or have a Thinkpad that doesn't support them (my X20 and R40 don't) then the above statement applies.