Backup battery which we removed from an Accenta / Honeywell house alarm panel. Can be used for other systems also, as here: Yucel/Yuasa Y2.1-12 Sealed Lead Acid Battery 12v 2.1ah Fire Alarm Panel Back Up https://amzn.eu/d/dnnszG9
Was installed approximately 18 months ago, so should have a good 3 years life left in standby mode.
Battery for house alarm panel (City of Bristol BS6)
This offer has been gifted to someone and is no longer available.