Why Battery Choice Matters in UPS Systems

In any uninterruptible power supply (UPS) system, the batteries are the heart of backup power. They determine how long critical equipment stays online during outages, how often maintenance is needed, and how well the system meets operational and sustainability goals. Choosing the right battery technology is therefore a critical step in ensuring uptime, reliability, and cost efficiency.

Today, two primary battery types dominate modern UPS designs: VRLA (Valve-Regulated Lead-Acid) - including advanced Pure Lead Acid models - and Lithium-Ion (Li-Ion) batteries. Each option has distinct advantages and trade-offs. Understanding how they compare across performance metrics, maintenance requirements, and application suitability is essential to making the right choice.

Understanding VRLA UPS Batteries

VRLA batteries are a sealed lead-acid technology commonly used in UPS systems across a wide range of installations. They are maintenance-free, compact, and widely available from multiple manufacturers.

Key Features:

• Sealed construction eliminates the need for electrolyte checks or water top-ups.
• Lower initial cost compared to lithium-ion options.
• Available in a wide range of capacities and ratings to suit most UPS models.
• Proven performance in standard runtime applications such as data rooms, branch offices, and commercial IT setups.
   

Pure Lead Acid Variant

For environments where reliability and longer design life (expected battery lifespan) are required, Pure Lead Acid (PLA) batteries offer enhanced performance over standard VRLA:

• Design life typically exceeds 10–12 years  in optimal conditions, compared to 5–7 years for conventional VRLA.
• Higher energy density and better performance in demanding applications.
• Lower risk of thermal runaway compared to conventional VRLA, thanks to improved thermal stability and purer lead grids.
• Temperature impact is still a consideration: For VRLA batteries, every 10°C above the recommended 20–25°C operating range can cut service life by around 50%.

Lithium-Ion UPS Batteries

Lithium-Ion batteries are increasingly used in modern UPS systems, particularly in high-density data center and industrial applications. They offer a longer design life (often 10–15 years), reduced weight, and improved charge/discharge efficiency.

Key Features:

• Faster charge times compared to VRLA, minimizing downtime after outages.
• Higher round-trip efficiency during both discharge and recharge cycles—typically 5–10% better than VRLA—reducing heat output and energy waste.
• Smaller footprint and lighter weight simplify installation in constrained spaces and reduce structural load.
• Lower total cost of ownership (TCO) over the service life due to fewer replacements and lower maintenance requirements.
• Integrated battery management systems (BMS) monitor voltage, temperature, and state of charge to ensure safe operation, extended battery health, and predictable performance degradation.
• Thanks to higher thermal resilience, Li-Ion batteries maintain performance over a wider operating temperature range, reducing cooling stringency and helping to lower energy use.

VRLA vs. Lithium-Ion Batteries Compared

How to Choose the Right Battery for Your Application

Selecting between VRLA (including Pure Lead Acid) and Lithium-Ion batteries comes down to matching application requirements with battery characteristics. Consider these steps:

1. Assess Runtime and Load Profiles

• For standard office IT equipment and smaller UPS installations, VRLA is often sufficient.
• For data centers and critical control systems requiring extended backup and high discharge efficiency, Li-Ion may be preferable.

2. Evaluate Total Cost of Ownership

• VRLA batteries have a lower upfront cost but may require more frequent replacements, increasing downtime and service labor.
• Li-Ion batteries, while more expensive initially, have a longer service life and predictable capacity fade, reducing operational disruption and lifecycle costs.

3. Consider Environmental Conditions

• If the installation environment has temperature fluctuations or limited cooling, Li-Ion’s resilience offers a clear advantage.
• For controlled indoor environments, VRLA remains a reliable choice.

4. Check Standards, Certifications, and Compatibility

• Ensure compliance with IEC and UL standards, plus UN 38.3 for Li-Ion transport and IEC 62619 for industrial battery safety and are fully compatible with the UPS model.
• Legrand solutions meet international safety standards to ensure seamless integration.

5. Factor in Space and Cooling Requirements

• Li-Ion options typically reduce cabinet room requirements by 50–80% and lessen cooling loads, making them ideal where space and energy efficiency are priorities.

6. Plan for End-of-Life Recycling

• VRLA: Widely recycled through established lead-acid recovery programs, with high material recovery rates.
• Li-Ion: Recycling infrastructure is expanding, but availability varies by region; ensure a compliant collection and disposal plan.

Applications for Each Battery Type

• VRLA / Pure Lead Acid:
  Suitable for standard data center racks, edge computing nodes, and branch office UPS systems where cost control and reliability are the main drivers.
• Lithium-Ion:
  Best for high-density data centers, industrial automation, and mission-critical environments where space, weight, and extended design life matter.

Legrand’s Approach to UPS Batteries

Legrand’s UPS solutions are designed to support both VRLA and Lithium-Ion battery configurations. This flexibility allows organizations to choose the technology that best meets their operational, energy, and budgetary requirements.

Our high-power modular UPS systems, such as the Keor FLEX, integrate seamlessly with Li-Ion technology to reduce footprint, improve energy efficiency, and extend service intervals—ideal for modern sustainable data centers. For traditional deployments, Legrand also offers VRLA and Pure Lead Acid battery cabinets designed to meet varied installation requirements with proven reliability.

Conclusion: Matching Technology to Your Needs

Choosing between VRLA (including Pure Lead Acid) and Lithium-Ion UPS batteries isn’t about which is “better” universally, it’s about selecting the right option for the application and operating environment. VRLA remains a cost-effective, proven choice for standard installations, while Lithium-Ion offers long-term benefits for high-demand, space-conscious, and sustainability-focused operations.

Legrand helps customers evaluate these options to ensure their UPS battery systems align with operational requirements, energy strategies, and long-term reliability goals. Explore our battery options and full UPS solutions on our Legrand Data Center site or consult with a Legrand expert to specify the optimal configuration for your installation.