The concept here is simple. Take a misdemeanor battery, then add an extra ingredient or two--and voila--instant aggravated battery. The words behind the aggravated battery describe why the battery is enhanced, like "with a deadly weapon", or "causing great bodily harm". Let's show you a few examples of how this works.
One way to take a misdemeanor battery and turn it into a felony aggravated battery is to alleged that the battery caused "great bodily harm". So, if you can prove that (1) an unwanted touching occurred, and (2) that touching caused 'great bodily harm', you've got yourself an aggravated battery. As an example, one defendant was charged with aggravated battery causing great bodily harm after a defendant shocked the victim with a stun gun. The victim testified that the shock caused her to lie down, and the stun gun caused her great pain, but she required no medical treatment and the stun had no lasting effect. The court overturned the defendant's conviction, finding that 'great bodily harm' requires more than slight or moderate 'harm'. [See Nguyen v. State, 858 So. 2d 1259 (Fla. 1st DCA 2003).
In another example of an aggravated battery charge that turned out to be just a simple battery, check out Gordon v. State, 2011 WL 6016913 (Fla. 3rd DCA 2011), where Gordon's aggravated battery charge was overturned due to the fact that the bruises caused did not require medical treatment, and eventually fully healed--thus not qualifying for "aggravated" status. For a more in depth analysis of this case, and the difference between an aggravated battery and a misdemeanor battery, check out my article "When Aggravated Battery is really only a Battery".
Which brings us to another way to get an aggravated battery, and that's with a "deadly weapon". The theory here is also simple. Take a misdemeanor battery, but rather than using your bare hands (a fist, or open hand slap, for example), you use a stun gun, and the state calls it 'Aggravated Battery with a Deadly Weapon", how does that work? Well, this is where definitions of a 'deadly weapon' play a key role in determining whether or not the charge is legit. Take our stun gun case above, for example. In that case, the court found that an aggravated battery with a deadly weapon charge was invalid as well, because for an object to qualify as a "deadly weapon", it must be designed to be deadly as contemplated by it's manufacturer. In the case of a stun gun, it's not designed, nor is it likely to cause great bodily harm, so the court in Nguyen (above) found that a stun gun does not qualify as a deadly weapon based upon it's design. However, sometimes the state can get away with charging aggravated battery with a deadly weapon if an ordinary item is used in a manner that is likely to cause great bodily harm. For example, if you take a stun gun to an intensive care unit at the hospital to kill an unsuspecting patient, the circumstances of the stun gun's use would qualify for 'deadly weapon' treatment. Household items like screwdrivers have been held to be deadly weapons based upon the manner of their use. Which brings us to the obvious, use of a firearm will always qualify as an aggravated battery with a firearm (and look out for those hefty mandatory minimum firearm sentences, typically 20 years on such cases).
Unfortunately, our legislature has done a poor job of defining what constitutes a "deadly weapon". So, lazy prosecutors across the State of Florida have filed deadly weapon charges for just about every household non-deadly item you can think of. Yes, stuff you would allow your baby to play with has been found to be deadly by some prosecutors. Lucky for us, we have some appellate courts which can review such nonsense, and overturn cases when necessary. To see the details on how a broomstick beating was overturned due to the fact that a broomstick is not "an instrument that will likely cause death or great bodily harm when used in the ordinary and usual manner contemplated by its design", check out my article "Can a Broomstick Be a Deadly Weapon?"