Originally Posted by BetaRambo
I would say that it is 95% likely that you have a loose connection in the charge path
The weak point is the mini-micro-uber-wimpy flange connector terminals on the battery. Mine did the same as you describe, and I found a tear in one of the battery "posts." Look for light corrosion in the female connectors to the battery.
I replaced mine with "normal" 12v deep cycle batteries with real connectors. Problem solved.