5 Common Causes of UPS Failure

Today’s uninterruptible power supplies (UPSs) are designed to be reliable and afford your customer the protection they need. Yet aging UPSs can and do fail. Here are the five most common causes of UPS failure…and how you can help your customer prolong UPS life.

Component Function Life expectancy Factors affecting life expectancy
Battery Provides power when utility power is not available 3–5 years

· UPS placement

· Ambient temperature

· Cycling frequency

· Maintenance

· Battery chemistry

· Battery storage

Fans Cools the UPS Up to 10 years

· Load on the unit

· Ambient temperature

· Frequency of use

· Duration of use

Electrolytic capacitors Smooths out and filters voltage spikes Up to 10 years

· Ambient temperature

· Humidity

MOVs Protects circuits against excessive transient voltages Variable · Depends on the number and severity of surge events
Relays Helps UPS transfer modes Variable · Abnormal cycling

So how can you help customers prolong the life of UPS components?


The life expectancy of VRLA batteries will fluctuate greatly depending on UPS placement, ambient temperature, cycling, maintenance, battery chemistry, and battery storage. Helping customers understand these conditions and how to be proactive will help maximize battery life and prepare them for any imminent power failures.


Ensure that customers keep the ambient temperature within the specified range, monitor the UPS for unusual or frequent cycling, and choose a UPS that can support the attached load.

Electrolytic Capacitors

Every 10°C (18°F) decrease in temperature doubles capacitor life, so ensure that customers monitor environmental temperature and keep it within the specified range to improve life expectancy.

Metal Oxide Varistors (MOVs)

MOVs typically fail after exposure to frequent and/or extreme voltage spikes. Let customers know about the potential for failure so they can proactively identify and correct issues.


Failure under normal circumstances is unlikely, but an incorrect or malfunctioning firmware setup and unusually high cycling can result in overuse and eventual failure. Again, help your customer understand these conditions so they can adjust firmware settings before damage occurs.

Read more in White Paper 210: Single Phase UPS Management, Maintenance, and Lifecycle. Or contact your APC by Schneider Electric representative to discuss how you can help your customers with UPS maintenance services.

To learn more about upgrading and replacing batteries and UPSs, visit http://apcpartnercentral.com/ups

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