The dashboard for the Zip, the email notifications, and the Zip itself have always complained spuriously to me about the low battery condition. The battery state report *is* unreliable.
However, even though it "cries wolf" quite often, my Zip has never exhausted its battery without telling me about it. Put another way, one of those false alarms about the battery being low is correct: just the last one, though.
It's a hard engineering problem. The level of exhaustion of the lithium batteries (non-rechargeable primary cells) cannot be easily determined by the voltage of the battery. They maintain their voltage quite steadily (depending on temperature) until they very rapidly drop dead.
