Does it have some type of switch to select either 7.2 to 9.6? If not then I would say it's safe to assume that it will charge anything from 7.2 up to 9.6 including 8.4. I use a 9.6 charger on my 8.4 pacs all the time. It's more important as to how much the Mah rating is as to how well it will charge or over charge the battery.
Have Gun Will Travel
If the world is going to Hell in a hand basket...I want to be the one holding the handle.