UPS battery types — VRLA versus lithium-ion (lifespan and replacement)

The UPS uninterruptible-power-supply guide describes the VFI/online classification and autonomy time of a UPS in accordance with IEC 62040. An aspect that is often overlooked in practice is the choice of battery type within the UPS itself: VRLA (valve-regulated lead-acid) or lithium-ion.

Lifespan and cycle durability

VRLA — typical lifespan of 3-5 years under regular UPS use, with a cycle durability on the order of 500 charge/discharge cycles.
Lithium-ion — typical lifespan of 10-15 years, often the entire service life of the UPS itself, with a cycle durability running into the thousands of cycles.

This translates directly into the number of replacements over the service life of a single UPS: a VRLA battery set typically needs to be replaced two to three times (for example around year 4 and year 8), whereas a lithium-ion set often outlasts the UPS without needing replacement.

Maintenance frequency

Lithium-ion batteries typically require around one maintenance visit per year, versus around two per year for VRLA — a consequence of the greater sensitivity of lead-acid cells to temperature and ageing.

Trade-off: purchase price versus total cost

Lithium-ion UPS batteries have a higher purchase price than VRLA. Over the service life of the UPS (total cost of ownership), however, this difference is often offset by the avoided replacement rounds and lower maintenance frequency.

Note: the exact payback period depends on the specific UPS power rating, the application (autonomy-time requirement) and current prices — this article provides the qualitative trade-off, not a universal calculation example.

Practical relevance

For a horticultural business or commercial building with critical climate computers or control systems (see also the UPS guide for the N+1 redundancy trade-off), the battery choice has a direct effect on maintenance planning: a VRLA solution requires a recurring replacement budget and schedule, whereas a lithium-ion solution largely removes this risk over the UPS's service life.

Common mistakes

Only looking at the battery's purchase price without weighing the total cost over its lifespan (replacement rounds, maintenance).
Not replacing a VRLA battery set in time — an aged lead-acid battery can no longer achieve the required autonomy time, and this often only comes to light during an actual power outage.
Not accounting for compatibility between the chosen battery type and the charging electronics of the existing UPS when later switching from VRLA to lithium-ion.