Security & Fire Protection Systems/low battery message


Hi, I have a FBII xl-31 installed in 1993. I Just replaced the back-up battery for the third time in three years. Each time, the keypad display said I had a low battery and would start to chime. I checked the new battery voltage and showed full strength (12 volts). The low battery message appears once or twice a day, sometimes dissapearing by itself. I checked the three fuses and all are good. Could the systems' behavior be related to dust ?? I'm not sure how to remedy this on my own. Any suggestions?? Thx Paul

Hello Paul, and thanks for your question.

A battery a year is unusual. They should last longer than that.

Here are the possibilities.

The battery isn't charging properly. Causes could be (a)corroded or poorly connected spade lugs on the battery; (b) the transformer isn't performing as it should because the connecting wiring is too long or not of the correct gauge; (c)the charging circuit in the control is failing, or (d) the alarm's accessories are drawing more power than what the charging circuit is providing.  

I'd check the battery connections first. And second, I'd suspect the control may be failing, given its age.

I'd discount (b) since the alarm has been in service for many years. And (d)? Unless you've added accessories that draw additional power form the control, I'd discount that as well.

About your measurement of the battery, if you make the measurement with the AC power on and the battery connected, you're not getting an accurate reading because of the charging current. So disconnect the AC power, and then take the measurement.

I hope this helps!

Best Regards,


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Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


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