Douglas Krantz - Technical Writer - Describing How It Works
Go to the Writer Home Page of Douglas Krantz -- Describing How It Works
Go to the Fire Alarm Operation Map Page of Douglas Krantz - Technical Writer
Go to the General Electrical Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Description Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Installing Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Maintaining Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Testing Map Page of Douglas Krantz - Technical Writer
Go to the Fire Suppression Map Page of Douglas Krantz - Technical Writer

Fire Alarm -- Maintenance

When should standby batteies be replaced in a fire alarm system? Every Year? 2, 3,4, 5 years? Only when dead?
The NFPA Code indicates when to replace the batteries, but the NFPA Code only indicates the worst case scenario.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






When Should Fire Alarm Batteries Be Replaced?

By Douglas Krantz

The 2007 NFPA72 shows in Table 10.4.4, Item 6(d)(1), that the sealed lead-acid batteries used for battery backup in fire alarm systems need to be replaced within 5 years of manufacture. The NFPA wants the batteries replaced because the battery capacity is down to about 80% by that time.

Battery capacity, the amount of amphours in a battery, changes over time. In the first few months after manufacture, the amphour capacity of the average battery increases a few percent. For several years, this capacity doesn't change much. Near the end of the battery's useful life, the amphour capacity starts to taper off. At 5 years, it's down to about 80% of rated capacity.

If the NFPA requires replacement at 5 years, why do most fire alarm service companies replace the batteries after 3 or 4 years?

The answer is timing.

At about the same time each year, fire alarm systems are inspected. Because the battery's stamped date code is the manufactures secret, the service company has to go by the date of installation, not by the date of manufacture.

The trouble is, after manufacture, it's usually a month or two before the batteries are installed in the first place. This month or two gets added to the NFPA's 5 years, making the total time more than 5 years from the date of installation.

Rather than figuring out the date code stamped on the battery, and then trying to time the replacement at exactly 5 years, most fire alarm service companies decide to replace the batteries after 3 or 4 years of service. That way, usually, the batteries are replaced before they go bad.


More Articles

Do Amp Hours Start on Backup Batteries When the Alarms Go Off? -- The backup batteries are 8 amp hours (8 AH), but do those amp hours start when the alarms go off or do the 8 AH start as soon as I connect them to the panel? ... Read More

Why are Battery Date Codes so Cryptic? -- For safety reasons, the NFPA Code requires the replacement of fire alarm batteries within 5 years of manufacture...Read More

Can the Booster Power Supply be Installed in the Ceiling? -- The fire alarm system isn't going to be removed after the warranty period; the fire alarm system is going to be in place as long as the building stands. Not only that... Read More

Do You Have to Replace Fire Alarm Batteries in Pairs? -- The question is asked: In a fire alarm system, where backup batteries are wired in series, can the batteries be changed out one at a time, or do the batteries have to be changed out in pairs? Remember that the... Read More



Popular Articles

What is a Stair Pressurization Fan (SPF)? -- In case of fire in a high rise building, an SPF uses clean outside air to pressurize the air in stairwells. The pressurized air helps people escape... Read More

How Does Class A Fire Alarm Wiring Work?-- Fire alarm systems save lives and protect property. Fire alarm systems also break down because... Read More

What's the Difference Between Class A and Class B? -- The Fire Alarm System is a Life Safety System - so the occupants of a building can escape quickly, the idea behind a Fire Alarm System is that it will provide a warning that there is a fire. The trouble is, if something is wrong with the system, like a wire is broken somewhere in the building, the Fire Alarm System... Read More

What is a Flyback Diode? -- Someone Thinks the Flyback Diode is Important. Manufacturers all over the world spend good money installing these diodes, they must think they're ... Read More

What is a Waterflow Switch? -- The fire alarm waterflow switch, a delayed action mechanical/electrical assembly, is a conventionally wired fire alarm device. The fire department reacts... Read More

What Should I Do When the Fire Alarm Sounds? -- When the alarm sounds, as caretaker for an apartment building, what should you be doing? "I would never suggest turning off the fire alarms, or in any way... Read More

What is a Fire Alarm System? -- Long ago, as earliest method of spreading the word of fire danger, people shouted "Fire!" Depending on the circumstances, people would run... Read More

What Does E=IR Really Mean? -- If it isn't just a word, and it isn't really something to be memorized in order to pass a test, what do the letters in Ohm's Law really mean?... Read More