JP13 battery draining very quickly

I recently bought a used JP13 that had a faulty battery box. I switched out the box & installed a new battery, in early February. I never leave a cable plugged in to the guitar unless I’m plugged into an amp, so I’ve probably only used it plugged in for maybe 8-10 hours over the past month. Plugged it in today & no signal, battery was dead.

JP13 owners – what battery life do you typically get in your JP13? Is it possible that there’s a parasitic drain that could cause the battery to drain with nothing plugged in? Thanks