I try to keep mine charged at all times... 2or3 so I'm not caught out. But they've been messed with. I can't have 2 on at the same time. If I have one working I can power it. If I press the second with cartridge on it the battery just flashes like is not charged. If I take top part off the button will go as it should. I'm really embarrassed but how in the HELL is this possible. Thx for reading. Answers greatly appreciated.