Active pickups in a way are built in pre-amps.
They have a higher output then passive pickups, they need more electric power for that, that's why there is a battery.(those pickups dont use alot of power, the batteries last for about 600 hours)
But that's not the only difference; passive pickups have AC (alternating current), while active pickups have DC (direct current). So it's not possible to make a passive pickup active by attaching a battery.
Also, if you install an active pickup in your guitar, you need to make some adjustments(changing pot-meters, output plug), especially when you don't make the whole wiring active.
It's best to let a tech work on it, cause if you don't know what you're doing, you could ruïn your new pickup.
Greetz, trendkillah
