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Life Cycle of a UPS Battery

The following four factors determine the lifespan of a UPS battery:

Battery Life: Design Life vs. Actual Life

Determining battery life can be a tricky business. Battery life is often promoted based on design life, that is, how long the battery can be expected to perform under ideal conditions. Estimating actual battery life relies on taking into consideration the four factors that can impact battery life.

Batteries have limited life, usually showing a slow degradation of capacity until they reach 80 percent of their initial rating, followed by a comparatively rapid failure. Regardless of how or where a UPS is deployed, and regardless of its size, there are four primary factors that affect battery life. These are ambient temperature, battery chemistry, cycling and service.

1. Ambient Temperature

The rated capacity of a battery is based on an ambient temperature of 25°C (77°F). It is important to realize that any variation from this operating temperature can alter the performance of the battery and shorten its expected life. To help determine battery life in relation to temperature, remember that for every 8.3°C (15°F) average annual temperature above 25°C (77°F), the life of the battery is reduced by 50 percent.

2. Battery Chemistry

UPS batteries are electro-chemical devices whose ability to store and deliver power slowly decreases over time. Even if you follow all of the guidelines for proper storage, usage and maintenance, batteries will still require replacement after a certain period of time.

3. Cycling During a Utility Power Failure a UPS Operates On Battery Power

Once utility power is restored, or a switch to generator power is complete, the battery is recharged for future use. This is called a discharge cycle. At installation, the battery is at 100 percent of rated capacity. Each discharge and subsequent recharge reduces the relative capacity of the battery by a small percentage. The length of the discharge cycle will determine the reduction in battery capacity. Lead-acid chemistry, like others used in rechargeable batteries, can only undergo a maximum number of discharge/recharge cycles before the chemistry is depleted. Once the chemistry is depleted, the cells fail and the battery must be replaced.

4. Maintenance

Service and maintenance of the batteries are critical to the reliability of the UPS. A gradual decrease in battery life can be monitored and evaluated through voltage checks, load testing or monitoring. Periodic preventive maintenance extends battery string life by preventing loose connections, removing corrosion and identifying bad batteries before they can affect the rest of the string. Even though sealed batteries are sometimes referred to as maintenance-free, they still require scheduled maintenance and service. Maintenance-free simply refers to the fact that they do not require fluid. Without regular maintenance your UPS battery may experience heat-generating resistance at the terminals, improper loading, reduced protection and premature failure. With proper maintenance, the end of battery life can be accurately estimated and replacements scheduled without unexpected downtime or loss of backup power.

Battery Disposal

Batteries that are replaced can still contain a significant amount of hazardous waste, including the electrolyte and lead. Therefore, you must comply with EPA guidelines for the disposal of all UPS batteries. There are essentially two main categories of disposal, for spent batteries and for spills. The primary ways to handle these two categories are:

Spent Batteries

Send to secondary lead smelter for recycling.

Spilled Batteries

Place neutralized, leaked material into sealed containers and dispose of as hazardous waste, as applicable. Large water-diluted spills, after neutralization and testing, should be managed in accordance with approved local, state and federal requirements. Consult state environmental agency and/or federal EPA.

Recycling

Recycling lead-acid batteries is one of the most successful recycling efforts in the world. According to Battery Council International, more than 97% of lead acid batteries were recycled between 1997 and 2001. Many states require lead-acid batteries be recycled. Battery recycling is a service Power Management solutions offers that eliminates the customer’s effort and cost of proper battery disposal.