How to charge Lithium Batteries

I was always told that the NiCad batteries always needed to be discharged almost completely or they would develop a charging memory and not charge properly, and this would shorten their life. I know this was accurate, and covered all nicad cell batteries, cordless tools, and more.
Now we seem to be seeing a lot of these lithium batteries in cellphones and other things. should these also be discharged on occasion, or can they just be charged on a regular basis before they completely drain?
I'm asking because the lithium battery in my cellphone is getting weak, and wont hold a charge very long. I have never intentionally let it totally drain. Most of the time I just plug it in after a days use. It seems it is now draining from a full charge even with the phone shut off, (I dont use it often), it will be dead after sitting a week and not being turned on all during that week.
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http://arstechnica.com/gadgets/news/2011/02/ask-ars-what-is-the-best-way-to-use-an-li-ion-battery.ars

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snipped-for-privacy@myplace.com wrote:

I don't know the answer to your question, but I can propose an alternative:
Get a couple of replacement batteries via Ebay. They'll cost you about $4 each (compared to $35 at the Verizon or T-Mobile store) and you'll be good to go.
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snipped-for-privacy@myplace.com wrote:

You were told wrong. NiCads and NiMHs have to be deeply discharged only occasionally, and then never below 1.1V per cell, which causes damage. Look up "voltage depression". Generally, just charge normally, don't leave the charger connected all the time, let the battery run down once in a while, and if a tool is in storage, charge it every 6 months. Also charge a new battery or a battery that's sat uncharged for several months for at least 24 hours nonstop before using it, to equalize all the cells.

BatteryUniversity.com should have the answer to everything, but lithiums are the opposite of NiCads and NiMHs and don't like to be discharged much. That website also says to store lithiums at 40% of full charge, but I don't remember if they want you to discharge them to 40% or take discharged lithiums and charge them up to 40%. Don't charge a lithium battery with anything but a charger made specifically for lithiums or else they can be damaged, won't fully charge, or even explode (pressure builds up in all sealed cells, even NiCads and NiMHs).
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