Batteries initial charging

I have seen charging instructions that say to fully charge the battery before first use.
A friend of mine just bought a cell phone. He took it home and plugged into the charger and went online to activate it. He never once looked at the manual.
I tried to tell him he should charge the phone fully first. He said that only applies to devices that only work on battery only. Because he had the phone plugged into the wall that it was ok to use right away.
Who is right?
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He is
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wrote:

Your friend.
Most all cell phones use a lithium ion rechargeable battery. You are told to charge it first so that your phone is more than just a doorstop. Plugging the charger in and using the phone is perfectly acceptable. The phone draws off the charger and not the battery. This will not harm the Li-ion battery. The battery will just have to wait its turn.
For cordless house phones the story is different. They use Ni-Cads normally and sometimes NIMH batteries. They should be charged fully after installation especially with the Ni-Cads. This full initial charge is the best way to insure that the battery conditions itself to accept full charges.
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using it whilst plugged in is ok. Hell, using it with the factory battery not fully charged is ok. Not using it at all is ok. Charging it and not using it is ok. Hell, who cares?
s

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