Your card is formatted, talent's in place, and your gimbal is perfectly balanced. And just as you're about to roll camera.... your gimbal's battery dies. But wait? You charged your battery overnight, right? Even so, batteries, just like most things that involve power, have a shelf life.
The best way to avoid this nightmarish scenario is to test your batteries on a regular basis using a voltmeter/multitester. Among the many things it's capable of, a multitester can read the voltage of your battery and let you know if it has enough juice in it to perform. And just as easily, it can let you know if the battery is ready to be replaced.
If you don't own or readily have access to a voltmeter or multitester, then you can bring your battery(ies) into most electronics/repair shops or automotive garages. Most of these businesses will test your batteries for free.
Check multitester prices here.