Gutbucket has it precisely right. Follow his workflow and you should be ok.
With that said, I question the need for using the preamp at all. If the source material is loud enough, which it sounds like most of what your record is, the value added by the preamp is anywhere from questionable to downright risky.
A battery box is about as transparent as it gets so if the mics+bbox alone provides enough signal, you're going to have to 150% confident that any 'coloration' imparted by the preamp is desirable. Transformer based preamps can, by popular opinion, impart some nice warmth or color to the recording, but otherwise it's mostly helpful to think of a preamp as something that simply amplifies the source signal as transparently as possible for no other reason that to reach acceptable recording levels.
All too often I see questionable, imo, advise that adding a preamp might improve one's recording. If the mics are already properly powered and reach acceptable recording levels, adding a preamp to the signal chain starts is really just encroaching upon 'snake oil' territory.