GEM beeping while driving

I have had this 2003 GEM car for a few months. I also purchased brand new Trojan batteries at that time. When I last used it I recharged the batteries then left it sit without charging for over a month. We were driving it today and it started beeping on a continuous basis. I had to shut the switch off and apply the parking brake to make it stop. It resumed beeping as I drove for another mile to get home. Does the beeping mean that the battery level is low?

Did you by chance use the blinker at some point? These are not self-cancelling, and if left on after about 30 seconds a beeping noise will occur until you turn it off.