My ADT Safewatch 3000EN system has two big lead-acid backup batteries type ca 1240, instead of just one backup battery! I understand this system is similar to the Vista 15P.
I cancelled my monitoring contract with ADT and I am now on my own. The system is about 4 years old, all hardwired. I thought of changing the system backup battery preemptively. Then I found two identical big batteries in the panel. It also has two wall wart transformers, both for 16.5V AC.
Battery leads (red and black) go from battery A into the Main Circuit Board without terminals. The leads from Battery B go to (come from) a small sub-panel marked Altronix AL 624 Power Supply/Charger. The two batteries do not seem to be interconnected (such as being in series or parallel).
What is the second battery for and how do I replace both batteries?