on my fenders with the J retro preamp I've installed a micro toggle switch to isolate the battery. You have to remember to turn the volume down before using it to avoid the 'thump'.
I prefer that to having a lead hanging loose & having to turn down the amp which is a double pain after a sound check.
You soon get used to turning down the volume first.
Another great thing is, if you use the bass in passive mode, I switch the battery off because it's still powering the amp even though it's not in use.
If you decide to do it: use the switch to break the hot wire, It's the negative wire that breaks at the jack socket with most preamps so breaking the hot wire totally isolates the battery when the bass isn't in use.