I doubt my problem is related to hotplugging. GPM definitely knew about both batteries when it shut down the computer (I had just looked at the battery info a little earlier and saw both batteries)
It seems more likely that there are two bugs that are being tracked in a single bug #. -- Dual / Two Batteries, shutdown on empty expansion battery. (GPM does not recognises second battery on hotplug) https://launchpad.net/bugs/60442 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs