dont be so high handed mate,how do you know its not the battery?do you have the pac tester?thats the unit we use ,it put dummy load on the battery,its no use using a test meter,or an electric thingy,this is a site that we profs give our free time to help you guys out,
we dont crit,but the search box top right contain hundreads of answers,after a mains fail the standy battery will power the system for at least 8 hours,after that the external sounder will trip till the battery powers done,then when the power restore it will recharge the battery ,and screwdriver thingy as you call it will only tell you there is power,not if there is a neutral return,
gts, October 2011