It's not normal at all. The backup battery should absolutely protect the RAM even if the main batteries are dead.
Do you know if the backup battery is getting charged? And I guess the memory power switch must be on since I don't think it works with it off. I guess you would need to remove main batteries, all cables and see if the RAM is still getting sufficient power. As to the serial port, yes when it's active it does cause additional power drain. -- John. >
