You have probably heard that it is not a good idea to store dry cell batteries in electronics. After a period of time they can leak acid, which corrodes whatever it touches. Makes a real mess of things.
The photo at right is a Ziplock bag from our abandon ship kit, which contains the batteries that power the GPS and VHF, and which goes into the ditch kit when we head offshore. You can tell by the yucky yellow stains that one or more of the batteries leaked, ruining everything in the bag.
We were in the habit of updating these batteries annually. We’ve now changed that to every six months when we are cruising.