VRLA vs lithium-ion UPS batteries
VRLA (valve-regulated lead-acid) batteries are cheaper to buy and work in almost every UPS, but they last a few years and age quickly in a warm room. Lithium-ion batteries cost more up front, last several times longer, weigh less and tolerate heat better, but only work in a UPS designed or approved for them. Eaton gives lithium-ion UPS batteries 10 to 15 years against 3 to 5 for lead acid [1], and APC expects most of its VRLA batteries to last three to five years [2].
Key facts
- VRLA service life: three to five years for most APC VRLA batteries[2]
- Lithium-ion service life: 10 to 15 years, against 3 to 5 for lead acid (Eaton)[1]
- Heat and VRLA: every 8 °C rise cuts VRLA life in half (APC rule of thumb)[2]
- VRLA operating range: 5 to 35 °C, with an average below 25 °C (CSB)[3]
- VRLA in storage: about 3% self-discharge per month at 25 °C (CSB)[4]
Service life and what it costs over time
The purchase price is the smaller part of the comparison. A VRLA string is replaced several times over the life of a UPS frame; a lithium-ion system may last as long as the frame itself. Each VRLA replacement brings the cost of the blocks, the labour, the disposal and the risk of the swap itself. For a site that keeps its UPS for a decade or more, the total cost often favours lithium-ion even though the first invoice does not.
Heat
VRLA life falls fast with temperature: APC’s rule of thumb is that every 8 °C rise halves it [2]. A battery cabinet in a warm plant room, or a room run warmer to save on cooling, uses up VRLA life well ahead of schedule. Lithium-ion is far less sensitive, which is one reason it suits edge rooms and closets that are hard to cool.
Weight, space and floor loading
Lithium-ion stores the same energy in a fraction of the weight and space. That matters in older buildings with floor-loading limits, in edge rooms, and anywhere a VRLA battery cabinet would take space the IT equipment needs.
Compatibility and safety
Lithium-ion is not a drop-in replacement. The UPS charger, its battery management and its firmware all have to support the chemistry, and the UPS manufacturer has to approve the battery system. Fitting lithium modules to a UPS designed for VRLA because they physically fit is not an upgrade.
Maintenance
VRLA strings need regular measurement block by block, because one weak block limits the whole string (see battery maintenance). Lithium-ion systems monitor their own cells through a battery management system, which reduces routine readings but does not remove the need to check alarms, connections and the room.
Standards cited
- IEEE 1188 (VRLA maintenance, as quoted by battery manufacturers)
Common questions
Is lithium-ion better than VRLA for a UPS?
It lasts longer, weighs less and handles heat better [1], but it costs more up front and needs a UPS that supports it. For a long-lived three-phase UPS in a warm room, it often wins on total cost.
Can I put lithium-ion batteries in my existing UPS?
Only if the UPS manufacturer supports lithium-ion for that model, with the matching battery system and firmware.
How long do VRLA UPS batteries last?
APC expects most of its VRLA batteries to last three to five years [2], less in a warm room.
Do lithium-ion UPS batteries need maintenance?
Less routine measurement, because the battery management system watches the cells, but alarms, connections, firmware and the room temperature still need checking.
Sources
- Eaton, Lithium-ion UPS FAQ, FAQ
- Schneider Electric, What is the expected life of my APC UPS VRLA battery? (FA158934), FAQ answer
- CSB Energy Technology, VRLA Battery User Manual (Operation and Handling, Rev Dec 2024), operating temperature
- CSB Energy Technology, VRLA Battery User Manual (Operation and Handling, Rev Dec 2024), storage
Updated