The cables on your garage door handle a lot of hard work and tension. Over the years they can fray and degrade. You should change them yearly to avoid the horrible accidents that can occur from these high pressure cables snapping or coming loose.
The backup battery system is a separate device that connects to your garage door opener. It's very useful during power outages and emergencies, as it provides your system with emergency power and allows it to continue to operate for a few hours.