Problem with a Jackson KBX bass

[HoddiDarko]

My friends Jackson KBX Kelly bass sucks the battery dry in just a few days, and he is not forgetting to unplug it.
He bought it used and the guy had installed a little switch on the backplate to kill the signal to the battery, and when my friend asked me to fix a few things about the bass he asked me to bypass that little switch because we thought that the previous owner just didn't know about unplugging the bass to save power. So apparently this switch was important since these electronic suck the battery dry in so little time.
This is not how these electronics work right? Could the be soldered wrong in some way or are we overseeing something simple?
The bass has these Duncan Designed "active" pickups, I guess they just have a preamp.

If you have no idea, then you can just recommend some other good, passive soapbar pickups for my friend? He plays pretty basic heavy metal most of the time, but also some thrash I guess.

[peabuddy]

check the jack. it has to be a 3 contact jack. I made the mistake of using a 2 contact jack( i had both black wires on the same contact) and it killed the battery like it was plugged in.

[Newc]

Yup. Or it could be a 3-prong jack wired wrong. I did that too

As for good passives, I really like the Duncan Designed bar-types that came in my Jackson C5-P.

[amimbari]

ya what they said, that's the solution bad or miswired 3prong jack....BTW, is that a red trans finish KBX with that switch?
You could take the preamp out completely, as those pickups will run fine by themselves, but the tonal control will be from the amp only obviously if he does that.