In that case get a battery try it , see if it's charging ok, no need to take panel off wall unless it's fried in some way
Maybe if you got more budget get a panel that can also do some wireless circuits and so on
Scanteonic ion40 might do you great DIY panel ,, (init databasher)
Logan be serious
If your going to use it then yes , engineer should check it's power unit, replace battery, walk test check external internal sirens and make sure it works
Better to have some kind of park these days , then you could Lao get a quote for a new model , just depends on you, be preventative
Careful tho many with faults if your buying off eBay or something , test it well , see what firmware version it has , somewhere firmwares like 7 and others were revised quite quickly due to bugs
I come across this often , DIY installs connected to the Internal customer network , and picked up on on if because passwords are still on default , and allot of them internal cameras around the house apparently secure various makes and models
https://www.bbc.com/news/technology-50760103
No the 48 would work , sure experts might agree
But if it was choice I would buy the 96 anyway , depending where and how you buy it , not much in the price
Customer calls , cqr carbon monoxide sensor activation, alarm silenced but detector sound still activating
Told them over phone open your windows and you garden door
I happen to be on route to another place with this in-between , got there sounder has cleared
What you think , detector faulty ? Boiler man tells them buy a portable detector before calling him out