Contrary to the in-game description, Charge's power doubling effect only applies to the Pokemon's next move, not its next turn. If the next move happens on that same turn due to Instruct, then the "next move" for the purposes of Charge 1 will be Charge 2, and Charge 1 would gladly double Charge 2's power except it doesn't have one.
Charge 2 will still apply to whatever move comes next, of course, but Charge 1 does not.
If you use Charge on one turn, but then on the following turn you use an item instead of a move, Charge will remain in effect until you actually try to use a move, whatever turn that finally takes place on. (Things like flinching or hitting yourself in confusion don't actually involve using a move, but they do involve attempting to, and will exhaust your active double-power effect from Charge if you have one.)