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Emergency Lighting Blog

News and Information for Public Egress, Building Safety and Government Compliance

Monthly Archives: June 2015

The Four Different Types of Rechargeable Batteries We Offer

At Emergency Lighting, we stock all the essential battery styles from top manufacturers to ensure your emergency lighting and exit signage is always up to the task when you need it most.

There are many variations of rechargeable batteries available depending on the specific needs of your application. See the descriptions below to find the right battery to meet your needs.

1. Sealed Lead Acid

Sealed Lead Acid or (SLA) batteries are the most reliable and widely used power source. They can recharge much faster than a flooded lead acid battery, and the calcium added to their plates helps reduce water loss. Sealed lead acid batteries can recycle the gases they produce and can prevent damage to the battery when the charge rate is controlled. These batteries must always be kept in upright positions and protected from leakage.

2. Valve Regulated Lead Acid

Similar to standard SLA batteries, VRLA batteries include a safety pressure relief valve. VRLAs are a great low maintenance power option and cannot spill their electrolytes if ever inverted. VRLA batteries can be used in applications where traditional flooded batteries cannot be used as long as their charging is well-regulated. In the event of an emergency VRLA batteries are a highly reliable option for your emergency lighting systems.

3. Nickel–Cadmium

Although seldom used today, NiCd batteries are still useful in applications requiring very high discharge rates because they can withstand such scenarios with little damage or loss of capacity. Nickel–Cadmium batteries are made in a wide range of sizes and capacities, from portable sealed types comparable to carbon-zinc dry cells, to large ventilated cells used for standby and motive power.

Compared to other rechargeable cells, NiCd batteries offer good cycle life and performance at low temperatures with fair capacity low internal resistance. Their true advantage is the ability to deliver practically full capacity at high discharge rates. However, their materials are more costly than lead acid batteries, and the cells have high self-discharge rates.

Since the battery is not a pressure vessel, ventilated nickel-cadmium batteries are safer, weigh less, and have a simpler and more economical structure. This also means the battery is not normally damaged by excessive rates of overcharge, discharge or even negative charge.

4. Nickel–Metal Hydride

NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell. Nickel–Metal Hydride batteries are good for high current drain applications because of their low internal resistance.

The disadvantage of NiMH batteries is their high rate of self-discharge. NiMH batteries typically lose 4% of their charge per day of storage. LSD NiMH batteries significantly lower self-discharge, but at the cost of lowering capacity by about 20%.