This question is a bit off-topic because it concerns a camera battery on a SI2K. But the SI2K is the indirect ancestor of the RED right? Close enough is good enough for a try my luck anyway.

I have two generic batteries which are patterned after the Dynacore batteries. They have a Dynacore 2010 controller board in them. One of the batteries became a bit erratic about four years ago and after charge, failed to show charge state with the test button. It also seemed to resist charge but that may have been the test button or the LED chain not lighting up. Whichever, I took the battery off duty, opened the case and could not seem to get it to work and moved on.

Now here's the strange bit. I got broken into a few weeks back. Fortunately the thieves walked right across one of the cameras and left everything techie alone but got a vintage violin, a 1960's Hohner harmonica a vintage stills camera vintage binocular and everything in the trinkets and beads department of value. Whilst tidying up the scatter of everything, I had another look at this battery.

It seems to have spontaneously healed itself. It had held charge for about three years since I last tinkered with it. Obviously I can't have confidence in it for reliability. If anyone has any clues on what to look for as a fault, any advice will be appreciated. The other identical battery is fine although it has experienced more use.