For a gun to be "in battery", the breech must be closed and locked.  Must the hammer also be cokked?

Yes, you have defined "in battery". Just like baseball...just because the batter is in the box doesn`t mean the pitcher is on the mound.

(or has to be)

CTM is correct.

 As far the word that YA censors...just use zero instead of o. That has always worked for me. There`s absolutely no reason for "c0cked" to be censored if used in the correct term.

NO.   in battery means the bolt is forward and locked or the slide is forward in firing position, etc.   The hammer is not part of the process. 

The interesting thing to me is, what's the difference between "charging" the firearm and putting it in "battery". I always thought that "charging" the firearm was working the bolt and making it ready to fire, but then, that could be putting it in battery as well.

It has nothing to do with the hammer.

In battery means the bolt has locked into the chamber and therefore safe for the round to be fired. Otherwise, when the round is fired it could throw the bolt backwards at such a speed and force that it could damage your gun and, perhaps, even cause the bolt to fly into your face as well as the super heated gas in the chamber leaking out and burn you.

NO.   in battery means the bolt is forward and locked or the slide is forward in firing position, etc.   The hammer is not part of the process. 

False. In a battery means that there is more than one all with a similar usage 

In battery refers to a round in the chamber with the action locked. Position of hammer or striker does not qualify in this term. That would be a condition, Condition 1, Condition 2 etc.