Tried a $30 dive computer case from Amazon, now my backup battery lasts twice as long
I usually keep my spare battery in a ziplock inside my dry bag, but last month a seal failed on a job near Port Hueneme and soaked everything. Swapped to a hard plastic case with a rubber gasket, the kind meant for phones, and noticed my backup battery holds charge way longer now. Guess the constant pressure changes in the bag were draining it slowly. Anyone else run into battery drain from storage setup, or is this just a me thing?
Cold is the real killer in my experience. I had a spare lithium battery in an unheated garage for a winter and it lost most of its charge sitting there. Brought it inside to room temp and it held fine after that. Pressure changes might play a small part but temp swings are usually what drains them. A sealed case helps because it keeps the temp steady, not just the water out. If your case has a gasket and stays shut, that's probably doing more for you than you realize.