Had a job in Tempe where the keypad kept giving a false low battery alert
It was a DSC Neo system and the homeowner was ready to cancel the whole contract over it. I spent like 4 hours checking the panel voltage, the battery itself, and the wiring run before I found a tiny bit of corrosion on one terminal in the basement. Cleaned it up and the alert cleared instantly. Ever had a simple fix take way too long because of one dumb little thing?
Classic DSC move right there. Those low battery alerts are almost never the actual battery. Always check for voltage drop on that long wire run first, a bad connection will do it every time. A multimeter is your best friend for tracking that down. Drives you nuts spending half a day on a five minute fix.
Totally agree with @simonl86 on the voltage drop. I've seen that thin 22-gauge wire they use for the battery loop get pinched or corroded at a screw terminal, causing a huge drop under load. Check the voltage at the panel with the battery disconnected, then check it right at the battery terminals while the system is armed. If you see more than a half volt difference, start tracing back for a green connection or a break.