Chrubuntu on Acer C7: SD card reader only works on AC power?

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http://unix.stackexchange.com – I have an Acer C7 chromebook on which I have installed Chrubuntu. Everything works great except that the SD card reader doesn't work when the computer is running from battery power. It recognizes the card and works perfectly as soon as I plug it into AC power. Is there a power management setting somewhere that I need to toggle to be able to use my SD card reader on battery power? (HowTos)