That's just what the bad battery pack I have did. I made a quick glance at the battery icon on the screen shortly before it acted up and it showed about half charge. A few puffs later nothing, looked at the screen and it was flashing weak battery. Thinking it might be a bad connection I popped the battery off and reconnected, same, tried it on my other dx, same. Hooked it up to escribe and it showed the middle cell was lower, that cell must have dropped below the cutoff under a load and then the board kicked the low batt. I don't remember what the numbers were and I didn't try to fire it to see what it would read, I just set it aside until today when I pulled it apart for the pics. Sounds like fullymax has some packs with bad cells. I'll check it with the meter and hooked to a board and escribe tomorrow.
ETA: Maybe a bad batch of fullymax's is out there and that triggered the big dump of these? Noticed this on ecig
Warranty & Returns | Ecig.com
The following list of products do NOT qualify for returns or exchanges.
Any e-Liquid
External Batteries
Wick/Coil