Uhm..the battery is not for an effect, it's for the onboard EQ. That's why without one it won't make any sound.
The battery usually holds for months (and even for 1 year+) - IF: you use a good brand battery and you UNPLUG it after each playing session - if you keep a cord plugged in, it will drain the battery.
When the battery goes eventually bad, it won't die all of a sudden: the tone will get muddier, distorted, then volume loss will occur until slowly fading out. You will have plenty of time to replace the battery. If you're still paranoid about it, just keep a fresh one in the bass case.
HOWEVER if you see the battery going dead in a matter of days or a couple of weeks (in spite of following my previous suggestions) then the bass has probably a faulty EQ or maybe the input connector is stuck in "IN" position (as if the instrument cord would be plugged in).
The Ibanez Club #143 | The Soundgear Club #12