My NBN backup battery was beeping; calling for its replacement.The alarm silence button didn’t seem to silence the beeping for long. As my installation was 3 years old, the battery was no longer covered by warranty.
Surely it is just a battery. However, the guide suggests that the battery is very particular, such as an emphasis on unusually-sized terminals.
As luck would have it, I had a spare battery from a 13 year-old alarm system with similar specs: same 12 volts, same 7.2Ah capacity, slightly smaller terminals. The battery had run two sirens and a strobe for over 10 minutes, so it was capable if just a little bit flat.
Before I swapped them over, I put both through a full recharge from my spiffy CTEK MXS 5.0. This charger will work down to 1.2 Ah on its motorcycle mode.
Charging the NBN battery worked a treat. I refitted the battery and the battery warning alarm has been silent since.
Charging the alarm battery failed; the charger would not progress from the first of its 7 phases so the battery was a brick.
The irony of all of this is that the backup battery does nothing to keep my VOIP online.