One problem I have come across when running a Acer 532H netbook on battery power is that it will suddenly hang and go into suspend or hibernate mode. It seemed to have occurred once the computer started to to get warm and the fan was about to change speeds.
There is a simple fix for this problem. You simply should update the BIOS. This will fix the suspend of hang problem on your Acer 532H netbook when running Ubuntu on Battery. As of BIOS v1.25 the hang problem does not occur.
If you left a Windows 7 partition on your machine then all you need to do is boot into Windows and go to the Acer Support website and select your netbook model. Windows 7 has a built installer that will flash the BIOS for you.
If you do not have a Window 7 partition, then you can head over this how-to flash your BIOS in Ubuntu post on the Ubuntu Forums.