Guides
Lithium-ion UPS batteries last longer, weigh less, take less space and tolerate heat better than VRLA, but cost more up front and bring their own safety rules. VRLA remains cheaper to buy and familiar to maintain. The right choice depends on the UPS's remaining life, the room and the total cost over that life.
Lithium-ion lasts roughly two to three times as long. Vertiv puts lithium-ion UPS batteries at 8 to 10 years or more, 2-3x the life of VRLA, and Eaton's component table gives average recommended replacement at 10 years for lithium against 4 for VRLA. Eaton's battery paper adds the reality for VRLA: often sold with a 10-year design life, but replaced every four to five years on average in UPS use. Over a UPS life of 15 years or more, that is the difference between one or two lithium strings and three or four VRLA ones.
| Characteristic | VRLA | Lithium-ion |
|---|---|---|
| Energy density | Moderate | High |
| Lifespan | Medium | Long (approx. 4X) |
| Weight | High | Low |
| Footprint | Large | Small to moderate |
| Recharge | Moderate | Fast |
| Maintenance cost | Moderate | Low |
| Cooling required | Moderate | Low |
| Battery management | Optional | Built in |
| First cost | Moderate | High |
Relative values from Vertiv's characteristics chart (SL-70120). Note that Vertiv's chart and its later article give different life multiples (approx. 4X and 2-3x); the conservative figure is the one to plan with.
Lithium-ion recharges faster and survives more cycles. Vertiv notes that lithium-ion batteries recharge at a faster rate than VRLA and can complete two or three times as many charge and discharge cycles, depending on the chemistry. On a site with frequent short outages or generator tests, that matters: each discharge wears a VRLA string, and a fast recharge means the battery is ready sooner for the next event. VRLA keeps real advantages: a lower purchase price, reasonable reliability and moderate maintenance costs, which is why Vertiv calls it the predominant UPS choice for decades.
Because VRLA life falls quickly in heat. Vertiv states that VRLA needs an ideal 20-25 °C, while lithium-ion UPS batteries typically withstand up to 50 °C without degradation, which allows placement in rooms without dedicated cooling. For VRLA, every degree above its target costs life; see UPS battery life.
It is when it is built and installed to the rules that apply. Vertiv's safety paper describes battery management at the cell, module and cabinet level, cells covered by IEC 62619 (cell construction and battery management), and a fire code section that requires UL 1973 listing, an approved battery management system monitoring voltages, currents, charge cycles and temperatures, and fire suppression. Makers design their data-centre chemistries and modules to minimise the chance of thermal runaway. Canadian sites follow the codes their authority having jurisdiction applies, so the installation is reviewed with them.
Switching an existing UPS needs the maker's approval and a compatible lithium-ion system with its own battery management; it is not a block-for-block swap. For VRLA replacement strings for data-centre UPS, see the data-centre UPS battery page; for battery service, UPS battery repair and replacement.
Less than VRLA, by Vertiv's comparison, but they still need inspection, monitoring of the battery management system and the UPS's own checks.
Only where the UPS maker supports a lithium-ion system for that model; it needs a matching battery management system and settings.
Vertiv cites up to 50% TCO savings over the system's life from longer life and lower maintenance, despite a higher first cost.
Vertiv gives an ideal 20-25 °C. Higher temperatures shorten VRLA life.
Sources, checked 2026-10-04:
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