Emergency Light Circuit Boards

All emergency lights include a small circuit board. This board controls all functions of the emergency light. If the battery is the heart of an emergency light, then the circuit board is its brain. It has three basic functions:

• Insure that the battery is fully charged.
• Convert the AC power which the unit is receiving from the building’s electrical system to DC power to power the lamp & charge the battery.
• Switch from electrical power to battery power in the case of power loss.

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While each of these functions is fairly simple, they need to work exactly right, every time. Failure of any part of this process renders the emergency light useless. Your regular monthly maintenance tests, utilizing the test button included in the emergency light, insure that all parts of this circuit board are functioning properly.

Insuring Battery Charge

While it would seem that connecting a battery to the correct power source should be enough to charge it, this is not so. Batteries last longer when they are trickle charged, instead of rapid charged. Additionally, the amount of current sent to the battery must reduce as the battery reaches its full charge. Overcharging of batteries causes overheating, reducing their life, and can even cause batteries to explode.

Browse Our Replacement Emergency Light Battery Category.

Converting AC Power to DC Power

There is no such thing as an AC battery. However, there are both AC (alternating current) and DC (direct current) bulbs available on the market. So, emergency lights are designed to function on DC power. The AC power which is supplied by your building’s system is converted through a half-wave bridge rectifier on the circuit board. This is the simplest method of converting AC power to DC power; by just allowing the positive part of the wave form to pass through to your DC circuitry.

Switching From AC to Battery Power

When there is a loss of building power, the circuit board switches from AC power to the battery backup. The circuit board is designed to take several seconds to accomplish this change. This is to prevent the lights from flickering every time the voltage level dips, such as from the turning on of an air conditioning unit. There is an electrolytic capacitor included as part of this circuit. Together with a resistor, they form a simple timer for this changeover. If you encounter your lights changing over immediately, it is an indicator that this capacitor is worn out.

Browse Our Most Popular Emergency Lights with Battery Backup

Replacement of Emergency Light Circuit Boards

Circuit boards in emergency lights should last 10 – 15 years. The limiting factor comes from the electrolytic capacitors. The electrolyte inside dries out over time rendering the capacitor useless; heat speeds up this drying process, reducing the life of your boards. If an emergency light fails to come on in a test, or power outage situation, check the condition of the bulbs and battery with a multi-meter. If both are functioning correctly, the circuit board needs to be replaced.

These circuit boards are fairly simple to replace. Open the case, disconnect the wires attached to the circuit board, and remove the screws holding the circuit board in place. You do not need to treat these circuit boards as static sensitive boards like circuit boards in computers.

These circuit boards are specific for the lamp type, battery type and battery voltage. Be sure to replace them with the same type board from the same manufacturer, or a board that the manufacturer says is an acceptable replacement. If you are unsure of what board you need for your lights, our trained staff will be glad to help you out.

We have a full staff of emergency light battery specialists here to help you find the right product. For more information, a quote, or formal invoice, please email the emergency light battery staff today or give us a call on our toll free 800 number to speak with a product specialist.

By Jonathan Carter