The charger chip's status line has a direct connection to the orange LED. The glowing pattern is, however, created independently by software.

A quick blink of orange (I've seen it look like red too, sometimes it's too quick to fully make orange) is usually caused by the charger chip sending out a pulse on its status line. This is used by the charger chip to announce fault conditions. If it makes quick flashes/blinks/flickers when you move the cable, then it's probably the charger chip complaining about input voltage disappearing, which would indicate a loose/glitchy usb port or cable.

"disconnect to save power" message is announced by the charging software whenever it detects charger disconnected, even if the battery is not fully charged.


If the battery is extremely discharged, so that it doesn't turn on at all (nothing on the display even when viewed in bright light, no reaction to keylock slider, etc), the battery charger will enter emergency charging procedure. The yellow light will shine brightly and steadily, no pulsing. It only pulses when the CPU is running and some sort of software has taken control.
If it however blinks/flashes faintly and repeatedly in a regular pattern, I think it was once every second or so, then it's a repeating fault announced by the charger chip doing a fault-reset-trycharge in a loop, and that fault would most likely be "extremely low battery voltage". It usually clears itself after awhile, unless the battery has been discharged so empty that it has self-destructed. In any case, the maximum length of the emergency charging mode is 32minutes, after which you need to replug if the system hasn't started and gone into pulsing yellow light yet.

The previous two paragraphs assumes fully functional and intact usb cable and usb port btw.