Sometimes when one of the two batteries is empty, my system will suspend (even though the other one is 100% charged). It doesn't happen often, but it's still annoying. upower -d: http://bpaste.net/show/170554/
Note that this bug was first reported to upower https://bugs.freedesktop.org/show_bug.cgi?id=55278
Please check out the latest version 1.4.1 and reopen if you can still reproduce the problem. My laptop has two batteries and everything works fine here, so this might have been fixed to your satisfaction too.