What Causes UPS Battery Failure?

Data center, server roomUPS Systems PLC offers UPS batteries and impedance tests as well as other kinds of UPS maintenance, such as checking power and cooling.

Unless it is serviced on a regular basis, your Uninterruptible Power Supply (UPS) can fail, which leaves you at risk of losing critical data. The main reason for that is UPS battery failure. We will be looking below at what causes UPS batteries to fail. Please contact us if you have any further questions.

An open circuit is the most common reason why a VRLA battery fails. Cell dryout is what most often causes this. Typically, UPS systems come with a Series connected battery system that provides the UPS System DC Bus with a high current. If one of the cells in a string opens, it breaks the entire string’s current. Briefly put, it only takes one failed battery cell to bring your whole infrastructure down.

Causes of Battery Failure


Temperature variances or incorrect temperature is the most common cause of UPS battery failure. The average stated life and optimum performance is achieved when the temperature of the lead-acid battery is maintained at 22 to 25 degrees Celsius. However, if the temperature falls under 22 degrees Celsius it will sustain damage or under perform; temperatures over 25 degrees Celsius reduces battery life but increases battery capacity. As a point of reference, every 8 degrees Celsius increase in temperature reduces the battery life by fifty per cent. So if batteries are working at 35 degrees Celsius, they are at risk of lasting just half of their 5- to 10-year expected lifespan.

UPS Battery – Empty Batteries do not last forever

Even when you follow all of the guidelines properly, UPS batteries will not last forever. UPS batteries, over time, lose their capability to provide power and will need to be replaced eventually.

Discharge Cycle of UPS Batteries

A major contributing factor to lowered battery life is how many battery discharge-recharge cycles a battery has undergone. The amount of energy delivered by a battery during a discharge directly impacts battery life reduction. The major reason for this is deteriorating battery contacts. Continuous discharging of batteries can cause them to prematurely reach the end of their life. Brief UPS activities caused by compensating sags and swells should be considered to be battery discharge cycles.

Measures of preventative maintenance include resting the battery terminal connections torque, thermal image scans for testing for abnormal or hot conditions, battery voltage testing, and visual inspection. If any irregularities are shown by the tests, we are able to determine how serious the situation is and whether or not the batteries should be replaced.

Regular battery maintenance and service are essential to ensuring that your UPS remains reliable. Not only does preventative maintenance remove corrosion and help connections, but it can also help to identify that a battery is unhealthy prior to it failing.


It is more likely your UPS batteries will fail if you don’t care for them properly. Regular maintenance is necessary as is their eventual replacement. A UPS maintenance health checkup done by UPS Systems will give a clear picture of your battery’s current state to provide you with peace of mind as well as help to prevent your UPS battery from failing. There is nothing you can do to cause your UPS battery to last forever. However, with the proper maintenance, care and storage, you can help to increase its lifespan and detect a failing battery before a catastrophe hits.