SEALED VS NiCad (NICKEL-CADMIUM) BATTERIES FOR EMERGENCY LIGHTS

EMERGENCY LIGHTS AND BACKUP BATTERIES

Emergency lights require some form of backup power to properly function when power to the building is interrupted. This backup power can be supplied by a generator, a power inverter, or, as is often the case, by some type of internal rechargeable battery installed on the lighting unit. Given that batteries are the most common way to supply power and light in an emergency backup situation, it is imperative that they meet several key requirements as mandated by building code and life safety laws; they need to be rechargeable, they must have a charge time of <24 hrs and they must provide enough power to keep lamps lit for a minimum of 90 minutes in the event they are activated.

BACKUP BATTERY TYPES FOR EMERGENCY LIGHTING UNITS

Emergency lights use two types of rechargeable batteries:

Nickel-Cadmium batteries (NiCad)
Lead-Acid batteries

Each of these has specific applications for which they are the best fit and both have certain advantages that make them the best fit for these applications.




SEALED LEAD-ACID BATTERIES AND EMERGENCY LIGHTS

Sealed Lead-Acid batteries are the most common type of battery used in emergency backup units although in recent years, as smaller LED lighting has become more popular, this is starting to change. Typically wet location emergency lights, inverter units, hazardous location emergency lights, and emergency lights with steel housings all use Sealed Lead-Acid batteries. There are a couple of reasons why Lead-Acid batteries are the best fit here:

Higher capacity in amp-hours stored
Lower up-front acquisition cost
Temperature does not greatly affect capacity and self-discharge

Lead-acid batteries typically come in 6, 12 and 24 volts and a variety of wattage capacities. This allows for a combo to be found that meets nearly every need. In instances where remote lamp heads are required, you will need to note and match the voltages, along with the number of remote heads, when purchasing so that the appropriate capacity Lead-Acid battery can be matched to the unit.

To determine the capacity required for your lighting unit, refer to the labels found inside the housing unit. If you do not find one, the existing batteries can often give you a strong indication, either by the model number, or the dimensions.

->GRAPHIC OF 6 VOLT 4.5 AMP SEALED LEAD-ACID BATTERY

When it comes to physical shapes and sizes, sealed Lead-Acid batteries for emergency units come in a number of different shapes and sizes. One of the most common is the 6 volt 4.5 amp Lead-Acid battery. It is found frequently in many different standalone emergency light units and is always in stock and available to ship as a replacement or retrofit battery, depending on your needs.


LEAD-ACID BATTERY MAINTENANCE

One of the great features of Lead-Acid batteries, is that they are essentially maintenance free. Current-day Lead-Acid batteries are sealed, unlike earlier models, which were not. Gone are the days of having to check water levels in Lead-Acid batteries and add water as needed.

Emergency lighting units require monthly testing. There is a “test” button on standalone units tests that the lamps and battery are functioning properly. For annual testing, you will need to disconnect the battery from the unit and check it’s voltage.

One thing to remember when checking almost any battery’s voltage, is that measured voltage should be slightly higher than the nominal voltage. When testing a fully charged 12-volt battery, it will normally read over 13 volts. With age, chemical components responsible for the electrical charge in the battery, lose their potential. We see this reflected in a reduction in voltage when fully charged. When a battery gives a voltage reading that = its stated voltage, it is very close to the end of its life cycle.

When checking your batteries using an actual battery tester is preferred to using just a multi-meter. A multi-meter only checks the existing voltage, minus any load. The battery tester will put a load on the battery and measure the voltage under load. False positive readings from a multi-meter are not an issue when using a battery tester and measuring voltage under load.

NICKEL-CADMIUM BATTERIES

Modern, low-profile, thermoplastic emergency lighting units typically use NiCad batteries due to their smaller size and lighter weight. Indoor area applications that do not require wet location, hazardous area or explosion proof emergency lighting units can benefit from the smaller size and lighter weight of NiCad batteries.


ADVANTAGES OF NICKEL-CADMIUM BATTERIES

Smaller size
Lighter weight
Faster charging time
No risk of acid spillage means that the battery can be installed in any orientation

NiCad batteries are lightweight, efficient and each cell is tested to guarantee its emergency light will illuminate for at least 90 minutes. NOTE: Unlike the sealed Lead-Acid batteries found in most popular standalone emergency lights, standard NiCad powered units do not typically carry enough excess capacity to also power remote heads. Therefore, if you need remote heads, be sure to verify the rated loads of the unit.


MAINTAINING EMERGENCY LIGHTS WITH NICAD BATTERIES



As is standard with any emergency lighting unit, NiCad battery backups should be “push to test” tested once per month and a full discharge test performed once per year. Every emergency lighting unit has a test function which interrupts power to the emergency light unit so that it runs only on the NiCad battery backup unit. When the test button is activated and the lamp(s) turn(s) on, the system is functioning properly and nothing further is required for another month, until the next test date.

Once per year, you will want to perform a full system test where building power is cut and the emergency lighting unit(s) do not have power for a full 90 minutes. This is mandated by federal law.

REPLACING NICAD BATTERIES IN EMERGENCY LIGHTING UNITS

It’s easy to spot Nickel-Cadmium batteries as they are cylindrically shaped often looking like AA batteries. Conversely, Sealed Lead-Acid batteries are block shaped.

The best device to test your batteries is a battery tester. This device will actually use the batteries existing power when giving a reading. Another option is a multi-meter. This is a good device, but is sometimes not the most accurate. When your battery is fully charged, the meter will give a voltage reading that is a bit higher than what the battery is rated. If the battery is on the verge of failing, a multi-meter can give a faulty reading. Another reason to use a battery tester in place of a multi-meter.

NiCad batteries need to be replaced with cells that have the same voltage. A replacement NiCad with too low a voltage will not sustain a 90-minute charge. On the contrary, a replacement NiCad with a voltage that’s too high, and you run the risk of damaging or even exploding your lamp heads! Never replace your Nickel-Cadmium (NiCad) batteries with Sealed Lead-Acid batteries! The charging requirements are very different and they require completely different circuit boards.


GENERAL GUIDELINES FOR REPLACING BOTH NICAD AND LEAD-ACID BATTERY TYPES

It is very important to only replace batteries with the same type. There are three criteria that define battery “type”:

Lead-Acid vs NiCad (Material composition)
Voltage
Amperage capacity

Voltage and amperage must be the same to make sure that the illumination provided by your lights is the same brightness level as before and that your emergency light unit remains lit for the required 90 minutes of time. If the voltage of the battery is too low, your lights will be dim; too high of voltage and you run the risk of permanently damaging the lamps. If your amperage rating is less than the original you are replacing, your lights will likely not remain lit for the required 90 minutes if the power goes out. In older emergency lighting units that use sealed lead acid batteries, while pushing the test button you may hear a buzzing sound which indicates that the batteries must be replaced.

As described above, there are a couple of major reasons why you cannot replace NiCads with Lead-Acid, or vice versa. First off, the charging requirements are very different for the two; NiCads recharge in roughly 3.5 hrs, while Lead-Acid batteries typically require a full 24 hrs to recharge. This also means that the circuit boards that regulate charging are different. Additionally, the connections each type are manufactured with are very different. NiCad batteries typically have wires attached to them with a plug, while Lead-Acid batteries typically have screw terminals or tabs that are hard wired in place.

If you have any additional questions regarding which battery type best meets your needs, or you need to place a rush order for any quantity, we have you covered. Please call us today at 844-394-8247 or email us at [email protected], for all your battery, lighting and egress signage needs!