Philadelphia Scientific has a 'Blinky' that alerts you when there is electrolyte in the tray, either from a boilover or over filling. If it's a major boilover it's fairly obvious because your racks are trashed but often you don't know that your battery tray has electrolyte in it until it's got a hole in. This 'Blinky' has a bright red/blue flash to tell you that you need to get the electrolyte out before any damage is done.