So I checked my device, it was plugged in already. It said "94% discharging ".
I unplugged it for a few seconds, then plugged it back in. I felt two brief pulses. Unplugged it, plugged it back in and it did it again when it registered a charge coming in.
I might liken it to when it vibrates a notification (the volume was all the down), but it wasn't the same. I don't recall anything similar happening.