Might b a silly question but I've seen in many reviews of passive guitars that ppl say they upgraded em to active pickups; how'd u do that? Where'd the battery go?

the battery will fit in the control cavity of most guitars, the same spot as the pots are now. You just wrap it with the foam they package it in, and close the cavity. Guitars like an Ibanez S may present more of a problem because it's so thin, but I know guys on here have installed them in that even. You have to replace the pots, and sometimes the input jack, but everything is supplied with the EMG's.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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Worst case scenario:

You have to get a surface mount battery box that requires routing. But it really isn't a bad idea considering it will have more of a "factory original" flair to it, plus it will ease battery changes in the future.
ESP LTD EC-256 and a Fender Deluxe VM
Dont "upgrade" to EMG's.. get some bare knuckles of sumthing and a noise gate and sort out your sloppy chops man
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If you want to solo then solo, if he wants to solo then he should solo, if your bassist wants to solo...slap him
Heres what you need:

25k pots
Stero Output Jack
The pickups

EMG includes everything when you buy their pickups, so that shouldn't be an issue. Your battery can probably fit in the control cavity of your guitar, but it can flop around and possible bridge shorts (due to the fact it has a metal casing) or neck wires loose. I would advise taping it down with electrical tape.