The preamp doesn't work without a battery. That includes the tone controls and gain control. If the bass doesn't have an active/passive switch to bypass the preamp, you wont get any sound with no battery installed. The preamp was installed to allow you to alter the tone of your bass without changing the amp settings. It;s also very handy when recording. Marcus Miller installed the NTNB in his Jazz bass because the engineers kept messing with his done, and that allowed him to fix it at the bass!
Since you are new to actives, just install an alkaline battery (no cheap stuff), and approach the bass with an open mind. You find that your amp's EQ might need to be tweaked since it was set up for a passive bass. Unplug your cable when not using the bass to stop the battery from draining. You can leave it plugged in during breaks at a gig. I used to leave mine plugged in at home all day when I was playing. The battery will last a long time, at least 6 months to a year. Just change it when you change stings. I've been using active basses since 1977 and never had a battery go dead on me during a gig.
And use the onboard tone controls! Even if you set them in one pace and leave them. An active bass set flat doesn't equal a passive bass because you will have more natural high end from the pickups even when the EQ is set flat on the bass. That's the true sound of unloaded pickups.
I usually goose the bass up a little and keep it there. That depends on the bass and the amp of course. And a little boost goers a long way. If you want a darker tone, turn the highs down a little, and boost a little lows.
