It is around 3 seconds k (maybe 3:25 but no less then 3 seconds), that is what my watch tells me.
Most people do know how long it takes to charge the thing thou, and that is that it goes off no matter what after a set time limit = easy to make Pichu pay (that was my backpack ok!
)(ok maybe someone who picks up this game may not know how long it takes to charge, or most of the world as well for that matter (most of the world btw))
Also it is good to ledge guard with ok even though it puts you at a
"great risk"
(its like all those other moves that put you at great risk such as PK thunder 2 out away from the ledge, or hey how about Falco's foward B away from the ledge while i'm taking about bad ideas? They tricks of great ledge guarding are Otherwise known as SDs which = bad if your trying to win) all those moves that put you at "great risk" by throwing yourself a long way off a cliff are just that good for ledge guarding.
Its as bright as using a small light gun to fire big really heavy bullets