So I have seen some camera threads where people are wondering why these cameras die. Here is what I have found with several;
A lot of these cameras have an internal battery that is used to run the real time clock. Some of them continue to run the clock even when the camera is not used and does not have batteries installed.
Some of these batteries are rechargeable (older) and some are coin lithium type. In either case I have been able to bring units back to life by replacing the internal battery. Although all of the internal batteries I have seen are soldered in place you can still replace them, just takes a little soldering skill.
If you are going to replace a rechargeable internal 3 volt battery with a coin battery be sure to put a diode in series with the positive so that the recharging current cannot make it to the new coin battery (it won't like being recharged).
Typically I just remove the old battery (mark the positive connection), solder some wire to the new coin battery and then connect the wire to the old battery pads on the board. Tape up the new battery and put the camera back together.
Maybe this will help someone, or at least help them understand what is happening.
I have completely destroyed a couple, but successfully repaired about 5 over the years.