In the old heavy relay panel days pre80's the battery was just stand
by duty no low battery indicator most panels.and 120 vac was taken to
box to a heavy wound transformer which could run several sirens.
When electronic boards came about the battery became integrated to the
board to provide the energy needed to run the sirens. and 120 runs to
a small wall transformer.
after changing battery it could take up to 24 hr till battery is
floated to proper voltage and panel sees it.
aprox 13.5 most panels.
Put a meter on the battery, disconnect the AC, monitor the battery for
one minute. At no time should the battery voltage drop below
(preferably get anywhere close to) 12 volts.
The panel periodically checks the battery. If you replace it, you may
have to wait quite a while before the LO Bat goes away.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.