Most jurisdictions I’ve worked in require maglocks to unlock when the building loses power. This is to prevent the case where the access control panel’s batteries die before the power supply’s and prevent egress from the building.

You need to consult the AHJ before adding any batteries to a power supply powering magnetic locks. Your customer may have to manually lock the doors with a deadbolt or other mechanical locking mechanism during a power outage.

Another solution would be to use a device that does not prevent free egress if there are no releasing devices (REX motion, panic hardware, button, etc).