FAQs for Using Lithium-ion Batteries with a UPS

Overview

The paper is a question-and-answer primer on using lithium-ion rather than valve-regulated lead-acid (VRLA) batteries in UPS systems. It compares the technologies on energy density, calendar and cycle life, recharge time, footprint, weight, cost and TCO, and summarises the six common Li-ion chemistries and cell packaging formats. Typical UPS cell ranges are Li-ion 70-260 Wh/kg, 10-15 year calendar life, over 1,000 cycles and 1/2-1 h recharge, against VRLA 15-50 Wh/kg, 4-6 years, 200-400 cycles and 6-12 h recharge.

On cost, an installed Li-ion system is roughly 1.2 to 2 times VRLA for the same power and runtime (as of 2018), down from about 10x a few years earlier. Over 15 years VRLA would likely be replaced 2-3 times versus none or one for Li-ion, and Li-ion UPS TCO is 10-40% lower than VRLA over 10 years (as of 2016). Li-ion systems take 50-80% less floor space and weigh 60-80% less. Charge efficiency is about 90% for Li-ion versus 80-85% for lead-acid, but BMS consumption makes total operating losses similar; the lead recycling rate is 99%.

Safety is addressed through thermal runaway susceptibility and the mandatory cell-level battery management system (BMS). Li-ion cycle life is often specified at 40 C versus 20-25 C for lead-acid, and keeping batteries near 25 C helps realise full runtime. Recommended storage is at 15 C and 20-40% state of charge, and Li-ion is not hot-swappable. Li-ion reaches 100% state of charge in 30 min to 1 h if the UPS charger can supply it, 5-10 hours sooner than lead-acid. The paper also covers UPS compatibility, recyclability, lifecycle carbon and IATA transport classes.

Key points

1. Li-ion: 70-260 Wh/kg, 10-15 year calendar life, >1,000 cycles, 1/2-1 h recharge; VRLA: 15-50 Wh/kg, 4-6 years, 200-400 cycles, 6-12 h.
2. Installed Li-ion cost is roughly 1.2-2x VRLA (2018), down from about 10x a few years earlier.
3. Over 15 years VRLA is replaced 2-3 times versus none or one for Li-ion; Li-ion TCO 10-40% lower over 10 years (2016).
4. Li-ion takes 50-80% less floor space and weighs 60-80% less.
5. Charge efficiency about 90% versus 80-85%, but BMS consumption makes total losses similar.
6. Li-ion cycle life is often specified at 40 C; near 25 C helps full runtime.
7. Storage at 15 C and 20-40% state of charge; Li-ion is not hot-swappable.
8. Li-ion reaches 100% in 30 min-1 h, 5-10 h sooner than lead-acid; lead recycling rate 99%.

Using it in design

• Battery catalog: chemistry (VRLA, LFP, NMC, LMO, NCA, LTO, LCO), specific energy, design and cycle life, rated temperature, footprint and weight per kWh, recharge time and compatible UPS models.
• Block Li-ion cabinets on a UPS not listed as compatible; warn that Li-ion is not hot-swappable for maintenance planning.
• Flag battery-room ambient above the chemistry's rated temperature and recommend 25 C for full runtime.
• In layout use the 50-80% footprint reduction and lighter floor loading; trigger a fire-protection and thermal-runaway review (NFPA 855, IEC 62619); in the TCO tool use replacement intervals (VRLA 4-6 yr, Li-ion 10-15 yr) and space value.

Who should read it

Design engineers and procurement teams choosing UPS battery technology.

Related standards

• IEC 62619
• UL 1973
• UL 9540A
• NFPA 855
• IEC 62040-1
• IATA Dangerous Goods Regulations

Publication details

Authors

Patrick Donovan; Martin Zacho

Publisher

Schneider Electric

Year

2018

Document number

WP 231

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation