There are several issues here.
Technical Issues with Bypassing the Backup-Battery
Half a century ago, there was no supervision of the backup batteries in a fire alarm system. If the backup batteries went bad, so they wouldn't support the fire alarm system at all, the owner of the building would find out about the bad battery either during the annual fire alarm inspections, or when there was a fire during a power blackout, whichever came first.
If the fire came first, the fire could get out of control and people could be injured before anyone found out about the fire. This kind of failure did happen.
As the designs and the electronics got better, the batteries were supervised. At first, supervising the batteries just involved having the panel check to see if the voltage on the batteries was present.
Then with improved designs, methods to check the power reserves in the batteries were designed into the panels. Nowadays, many panels have this ability to supervise the battery's power reserve.
The unstable voltages that you are observing is caused by the power from the auxiliary power supply being forced into the charging power supply for the batteries. When the battery charger is trying to supervise the backup batteries' power capability, the two power supplies are fighting each other.
Don't try to connect the battery terminals of the fire alarm system to anything other than batteries. Trying it won't work, and may cause further harm to the panel.
Trouble Power Supply Issues
Another way of looking at the backup batteries is that they are a "Trouble Power Supply".
According to the NFPA, all fire alarm systems are required to have two sources of power. If one source of power is lost, the other source of power is used to tell the owner that there is a problem. For a fire alarm system, one power source is the commercial power coming into the building, and the other power source is the backup batteries.
Yes, power outages happen.
Then again, I've seen where someone has accidently turned off the circuit breaker for the fire alarm system. It would be helpful if the building owner knew about the turned-off circuit breaker. If the batteries have been removed, not having a second source of power (backup batteries) means that the panel won't be able to warn the owner that the fire alarm panel is turned off.
It's significant. If the fire alarm panel is turned off, no will know about the turned-off circuit breaker until the next annual fire alarm inspection, or a fire occurs, whichever comes first. No one wants the fire to come first.
Remember, without backup batteries, if the fire alarm system's circuit breaker is turned off, the fire alarm system will fail.
Liability Issues
As long as the fire alarm system works, no one is going to notice, if, like suggested, the batteries are bypassed.
However, if there is a fire and the fire alarm system failed to detect the fire and warn anyone about the fire, someone will be in trouble.
Also, remember, all failure issues are passed downhill.
If there was a fire and the fire alarm system was turned off, the owner can say that the fire alarm company said "It's OK to bypass the backup batteries."
At this point, all eyes will then go onto the fire alarm company that bypassed the batteries.
The real question to consider here is whether the fire alarm company wants to save some money for the client by violating NFPA Code. Remember, violating the NFPA Code isn't just violating the law, it's taking on the responsibility for any failures if there's a fire.
Douglas Krantz
