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Home Frequently Asked Questions Replacing UPS Batteries How long should my UPS batteries last?

How long should my UPS batteries last?

There are a few factors that affect battery lifetime, and most manufacturers say they will last between 3-5 years in use. Here are a few things to consider about UPS battery lifetime.

UPS battery design life

Most batteries used in UPS applications are referred to as a 5 year standby design. This means that after 5 years under ideal float charging and temperature conditions the batteries will still have 80% of their original capacity. After this point the battery capacity drops off very quickly.

UPS battery operating temperature

Most batteries used in UPS applications are rated to operate between 20-25 degrees celsius. For every 8.6 degree increase over 25 degrees, the battery will degrade at twice the rate. This means a battery that spends 3 months of summer at around 40 degrees due to the heat inside the UPS would have degraded the equivalent of 12 months of its lifetime.

UPS battery discharge depth and frequency

Most batteries used in UPS applications are designed for standby use, as opposed to deep cycle use. Where a deep cycle battery is designed to be discharge and recharged regularly, a standby battery is designed to spend most of its life on float charge and to only be discharged by a small percentage of its total capacity. That is not to say that they cannot be discharged fully, but the deeper and more frequent the discharge the quicker the battery will degrade and the shorter the lifetime.

UPS battery charging

The suitable charging rate for UPS batteries is between 5% and 20% of their amp-hour rating. Charging at over 20% puts too much heat into the battery, charging below 5% means re-charging to full capacity could take a long time resulting in reduced capacity due to plate sulfation.

Now that we have covered all these things you can see that quite a few things can have an impact of the lifetime of your UPS batteries. Under the worst conditions we have seen batteries that failed in less than 24 hours, but these were overcharged in a 60 degree room. Likewise, batteries in a server room UPS that are kept at a good temperature and rarely discharged have been replaced between 6-7 years.

As for when you should replace you batteries, we recommend every 3-4 years, but more on that here.


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