Exit sign
Sealed lead acid and nickel cadmium emergency light battery
Emergency light and exit sign battery
Emergency lighting battery
All emergency lights and illuminated emergency exit signs use batteries to power the lights. These batteries are rechargeable to ensure continuous preparation and operation of the emergency lights. The circuit in the emergency light both charges the battery and ensures that the battery remains charged.
Battery type used in emergency lighting
There are two types of batteries for emergency lights; they are:
Sealed lead-acid battery (same type as car)
Nickel-cadmium batteries
Sealed lead-acid batteries are the most advanced rechargeable technology available. They are called lead acids because they contain lead alloy sheets and are immersed in acid. The acid decomposes the plate, producing charged electrons, which is electricity. Recently, the technology of lead-acid batteries has been improved to allow completely sealed units that do not require the addition of water to maintain acid levels.
Nickel-cadmium batteries are the first "dry" (no acid needed) rechargeable batteries ever. Since then, other technologies have been developed, but they are usually more expensive. In nickel-cadmium batteries, the two metals are separated by a dielectric (non-conductive) layer, causing the metals to react magnetically with one another, producing charged electrons that form electricity.
Which is better?
Both types of rechargeable batteries used in emergency lighting devices have advantages and disadvantages.
Advantages of lead-acid batteries:
Lowest cost
Better heat and cold resistance
Disadvantages of lead-acid batteries:
Larger size
Heavier weight
Must remain upright
"Deep riding" damage (let the battery lose power)
Advantages of nickel-cadmium batteries:
Small size
Lighter weight
Can be oriented in any direction
Longer life
Vulnerable to extreme heat and cold
Disadvantages of nickel-cadmium batteries:
higher cost
Must be fully dismissed on a regular basis (annual test is responsible for this matter)
There is a "memory", if it is not fully charged for the first time, it will never accept full charge
Typically, lead-acid batteries are used for steel enclosure emergency lights and nickel-cadmium batteries are used for thermoplastic enclosure emergency lights.
China Emergency Light emphasize that in the case of battery replacement, the same type of battery as the one originally included must be used. Replacing the battery type also requires replacing the board because the charging circuit is included on the board.
