Newbie to slackware wants to get max battery life out of lion battery. do I need to disconnect it when fully charged as was the case with nicads? Or is it wiser to leave it in all the time?

I personally do not own 1545 but there are some owned by office and have used it for some time. It does not seem to over charge and gives a good backup as well. But it is always wise to charge battery completely and then discharge it to its limit once in a while to keep battery healthy.

Does that apply to Li-ion or only to Ni-Cd?

My HP Compaq is left on almost 24/7** with no ill effects (approaching 3 years old)

**I'm old school: the theory is that on/off cycling is not good for electronics.

Moved to General (Not a Linux Question)

I leave my laptop plugged in and on most of the time if I'm not moving around. It doesn't seem to do any harm (that I can tell).

The only odd thing I've noticed is that sometimes (like now) the battery percentage will read 98% instead of 100%...not sure if that's a bug in the Xfce battery status panel applet or if it's genuinely the battery going a little screwy.

IBM sent out a message that said one should remove batteries when not actually using them. If you run your laptop as a home computer you probably should remove it. Batteries fail for two reasons. On is simply time. Second is number of charge cycles. Every time the computer is even slightly charging the battery it takes part of it's life.

When the battery is trickle-charging with the computer off, I don't think that qualifies as cycling.

The other part of the equation is temperature. Time at an elevated temperature will (all) electronic devices much more quickly.

As for removing the batteries, I would be concerned about losing some protection against transients.

I have seen it for Li-ion batteries. No knowledge about Ni-Cd. It is usually advised to discharge a battery completely after full charge at least once a month. But because you never plug out the laptop, it would not affect you. I have got Compaq at home at has lost most of battery power in just one and half years.

Yup, most of my laptops don't hold a really good charge any longer, generally 1.5-2 years and they begin having that drop off. However, replacement batteries are usually fairly cheap.

One of my laptops also does the 98% thing. ONLY one though. No matter how low I drain it, it NEVER shows above 98%.

...really??

I always had the impression that new batteries for rechargeable devices (e.g. laptops, handheld game consoles, etc.) were ridiculously expensive...guess I should have done a little of my own research before believing that.

I had to replace the battery on one of my old 1525's that I sold, the replacement was $70.

I'm looking at possibly replacing the current 1525's with the long-life 9-cell battery, and I seem to recall it's around $90, the 1545 being very slightly more expensive than that if I remember correctly.

A lithium ion charger can't overcharge a lithium ion battery, the battery will (eventually) explode if so, they do not tolerate overcharging.
The full discharge/recharge every so often is to recalibrate the battery meter, its simply trying to predict how much time is left based on the voltage, letting it go all the way down gives it a good discharge curve to base against.
Consumer grade lithium ion batteries typically loose 10-20% of their capacity per year. Heat causes them to loose capacity faster so removing the battery (away from cpu/etc heat) could lengthen the life slightly, but I find that its not really worth is as in a few years it will need replaced anyway and its nice to have it in for when the power does dip.

A lithium ion battery's life is determined by charge cycles. I have done much research on the subject and this is what I have come up with:

%100 of the battery completely dead is considered one charge cycle. So if you let the battery discharge %10, ten times and recharge this in theory equals 1 full cycle. But they do have a sweet spot that helps them maintain the longest life vs recharges.

%70 seems to be the "sweet" spot. Let the battery cycle down to %70 every so often then complete charge. The general rule of thumb is that the battery is good for up to 500 cycles. The battery does not like to be completely drained and one can expect a %2 lose of overall performance by letting the battery completely drain.

Lithium Ion batteries love to be charged for this reason but need to be discharged from time to time. Heat and other factors do play a role in the life of the battery. What I have done with my netbook and it seems to work well is leave it on charge for a week while in use, disconnect it from that charge one time a week and use down to %70 then charge. I do this with all my items that run on this type of battery.

My cellphone I charge all the time as it is fast and easy to run a cell down in the %70 range.

I have had very good luck with my batteries and I hope this helps.

There are two factors to life, one is charge cycle and the other is age. The typical MTBF for a consumer grade is 300 cycles, but there is also the 10-20% loss per year in overall capacity. Thats why I just leave mine in, they are going to go bad in a few years anyway, just factor the cost of replacement into the total cost of ownership.
Thats why other devices like my digicam's, gps, etc all run from AA's, an NIMH will go 10 years.