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UPS Battery FAQ

Q: What is the "end of useful life?"
A: The IEEE defines “end of useful life” for a UPS battery as being the point when it can no longer supply 80 percent of its rated capacity in ampere-hours. When your battery reaches 80 percent of its rated capacity, the aging process accelerates and the battery should be replaced.

Q: How can I ensure that my UPS batteries are maintained and serviced properly?
A: With proper maintenance, battery life can be predicted and replacements scheduled without interrupting your operations. These are IEEE and OEM recommendations for general maintenance:

• Comprehensive maintenance programs with a monthly inspection and more rigorous quarterly and annual checks
• Re-torque all connections, as required
• Load testing
• Cleaning the battery area, as required

Q: Do I have to replace my UPS batteries with the same brand of batteries?
A: If you use brand X and need to replace one or two batteries in the string you should use the same brand because they will have the same characteristics. If you need to replace the whole string then you can change brands with fewer risks.

Q: Are maintenance-free batteries maintenance-free?
A: Though sealed batteries are sometimes referred to as maintenance free, they still require scheduled maintenance and service. The term maintenance-free refers to the fact that they do not require fluid. Preventive maintenance is the key to maximizing your UPS battery service life.

Q: What about the disposal of batteries?
A: It is imperative that your service technicians adhere to EPA guidelines for the disposal of all UPS batteries. Remember, it is the owner's responsibility (and liability) to make sure these guidelines are followed.

Q: Is there any difference between the batteries used by smaller UPSs, from 250 VA to 3 kVA, and the ones used by larger UPSs?
A: While basic battery technology, and the risks to battery life, remains the same regardless of UPS size, there are some inherent differences between large and small applications. First, smaller UPSs typically have only one VRLA battery that supports the load and needs maintenance. As systems get larger, increasing battery capacity to support the load gets more complicated. Larger systems may require multiple strings of batteries, introducing complexity to battery maintenance and support. Individual batteries must be monitored to prevent a single bad battery from taking down an entire string, and putting the load at risk. Also, as systems get larger wet-cell batteries become much more common. The differences in battery maintenance between VRLA and wet-cell batteries discussed earlier in this handbook apply.

Q: Our facility was damaged by a flood and our batteries were partially submerged in water. What should I do?
A: The first concern in this situation is safety. Containing any contamination is critical to preventing hazards to workers and the environment.

The second concern would be to have the batteries load tested, have any or all replaced that do not meet the "useful life" criteria.

Q: My UPS has been in storage for over a year. Are the batteries still good?
A: As batteries sit unused, with no charging regimen, their battery life will decrease. Due to the self-discharge characteristics of lead-acid batteries, it is imperative that they be charged after every six to 10 months of storage. Otherwise, permanent loss of capacity will occur between 18 and 30 months. To prolong shelf life without charging, store batteries at 10°C (50°F) or less.

Q: Is it safe to transport sealed batteries?
A: Because they don’t contain liquid material there are no restrictions on shipping sealed batteries.

Q: What the difference between hot-swappable and user-replaceable batteries?
A: Hot-swappable batteries allow the batteries to be changed out while the UPS is running. User-replaceable batteries are usually found in smaller UPSs and require no special tools or training to replace. Batteries can be both hot-swappable and user-replaceable. Please check your user manual for details on your UPS batteries.

Q: How is battery runtime affected if I reduce the load on the UPS?
A: The battery runtime will increase if the load is reduced. As a general rule, if you reduce the load by half, you triple the runtime.

Q: If I add more batteries to a UPS can I add more load?
A: Adding more batteries to a UPS can increase the battery runtime to support the load. However, adding more batteries to the UPS does not increase the UPS capacity. Be sure your UPS is adequately sized for your load, and then add batteries to fit your runtime needs.

Q: If my UPS is in storage how often should I charge the batteries?
A: The batteries should be charged every three or four months to prevent loss of capacity.

Q: What is the average lifespan of UPS batteries?
A: The standard lifespan for VRLA batteries is three to five years, and for wet-cell batteries is up to 20 years. However, expected life can vary greatly due to environmental conditions, number of discharge cycles, and adequate maintenance. Have a regular schedule of battery maintenance and monitoring to ensure you know when your batteries are reaching their end-of-life.

Q: Why are batteries disconnected on small, single-phase UPSs when they are shipped?
A: This is so that they are in compliance with Department of Transportation regulations.

Q: If I have the serial number from the UPS or battery cabinet, can I find out how old the batteries are?
A: Every battery has a manufacturer date code that indicates when the battery was made. The battery or battery cabinet will also feature a sticker for each time the batteries have been recharged while in storage. Stored batteries require charging every six to 10 months, up to 18-30 months. Recharging stored batteries does not affect battery warranty.