You can check it like you would any other vehicle. You can use a multimeter to check the voltage before you start up for the day or go to an auto supply store to check it.
Mines was 11.7 volts the next morning before I started up. I left mines on a manual charge over nite and fixed it. It should be 12.5 volts.
When its dead-dead the remote wont work and you have to use your key to open your door. Then for some reason the alarm goes off like 5 second later.