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Why Battery Powered Exit Signs Do Not Exist

Why Doesn't My Battery Operated Exit Sign Work?

Battery Powered Exit Sign

Self-luminous exit signs are the most common crossovers for customers seeking battery powered exit signs. They require no electricity or ambient light to stay fully charged!

The most popular and cost effective exit sign solutions for most consumers is a standard, plastic LED exit sign. Unless you specify an AC-only model, these consumer signs will almost always include a battery backup system. So with that said, we still get questions from people asking if these basic models can run continuously without power. In this article we will shed some light on why battery powered exit signs do not exist.

We all know how typical AA, C and D-cell batteries work for household items like portable radios, flashlights and toys. The more you use it, the shorter the battery life. Even your automobile's beefy battery will drain pretty quickly if you try to run the radio or air conditioner without assistance from the engine.  

Exit signs are no different. After a few hours the battery will drain and they will deactivate, rendering the sign useless until the batteries are charged or replaced.

Battery Backup Exit Sign Illumination Types

Illuminated exit signs of today use light emitting diode (LED) technology, a highly efficient light source that uses between 3 and 5 watts of power at any given time. This is a huge leap over the inefficient bulbs of the past and create a much smaller carbon footprint.

Here's a quick comparison of LED, fluorescent and incandescent battery backup exit signs: 

 

ILLUMINATION TYPE

YEARLY ENERGY USE

YEARLY COST

LAMP LIFE

CARBON DIOXIDE POLLUTION

LED

44 kWh

$4

10+ Years

72 lbs

Fluorescent

140 kWh

$11

11 Mos

230 lbs

Incandescent

350 kWh

$28

2.8 Mos

574 lns

Certain LED signs are Energy Star rated, meaning they consume less than 5 watts of electricity at any given time. However, despite all the advantages in maintenance time and energy use, such signs will still die out after about two hours of continuous battery use.

Battery Backup Exit Sign Regulations

Several guidelines require exit signage to stay on at all times in any public building. If there is a sudden loss in power, the building will be plunged into darkness. Only the exit signs and a few other emergency luminaire's will stay lit, guiding occupants to safety. But if you install a battery backup sign without assistance from the building's power grid, you will be cited on your next inspection for non-compliance.

When it comes to staying compliant, two important documents to review are the International Building Code (IBC) and the NFPA 101: Life Safety Code.

IBC Section 1011.5.3 - Power Source

Battery Backup Exit Sign

LED Exit Signs with battery backup may sound like a miracle for areas without access to AC electricity. But further research will prove differently. 

Exit signs shall be illuminated at all times. To ensure continued illumination for a duration of not less than 90 minutes in case of primary power loss, the sign illumination means shall be connected to an emergency power system provided from storage batteries, unit equipment or an on-site generator. The installation of the emergency power system shall be in accordance with Chapter 27.

NFPA 101 Chapter 14.12.1.2

Illumination of means of egress shall be continuous during the time that the conditions of occupancy require that the means of egress be available for use, unless otherwise provided in 14.12.1.2.2.

There are several other associations and documents that also mandate the 24 hour use of internally illuminated exit signs including OSHA, IFC, ANSI and ISO; the list goes on and on. Again, a battery powered sign would make no sense because unless it were constantly maintained, the sign would fail to stay illuminated for 90 minutes in an emergency.

Electrical Design of Battery Backup LED Signs

Now that we are completely certain there are no battery operated exit signs, let's briefly discuss the electrical process of these safety markers.

During normal hours when the power is on, LED signage utilize the AC "house current" from the building's electrical grid. But AC current has a typical load of 120 or 277 volts; exit signs take either a 6 or 12 volt input. To prevent the exit sign from exploding, AC power must be dropped down and converted to a DC current. The voltage is brought down with a small intermediary transformer and the conversion to DC is accomplished by a half-wave bridge on the circuit card.

The converted DC current supplies power to the LEDs while the the battery is continuously trickle-charged to ensure emergency readiness. When a power outage or brownout occurs, the switching circuits inside the sign will automatically cutoff AC power, causing the battery to switch into action mode.

Conclusion

Now that we've cleared up all that confusion regarding battery backup/battery operated exit signs, it's time for the next step. Check out our great selection of LED exit signs, emergency light combo units and our sleek edge-lit models to choose the right sign for your business. Need a second opinion? Give us a call at 800.480.0707 anytime day or night.