Lithium Ion Batteries for the data center. Are they ready for production yet? (Chris Brown)

Overview

The article was published in the Uptime Institute Journal in 2019 and is by Chris Brown, Uptime's CTO. The author approaches lithium-ion batteries for UPS systems with a cautious engineering view. He notes that UPS duty is relatively gentle, meaning batteries on float charge face rare and short discharges. Li-ion failures seen in other industries are therefore less likely here, but the failure modes are not yet well understood. Typical UPS battery duty consists of rare transfers, with worst-case autonomy around 15 minutes before utility or generators restore power.

Thermal runaway is usually caused by a charger that fails to reduce current, or by physical damage to the battery. The author advises keeping Li-ion out of the data hall and in purpose-built battery rooms until failure modes are better understood. In the comparison, VLA/VRLA strings are replaced at about 80% of original capacity because capacity then falls quickly, while Li-ion degrades gradually and predictably. Li-ion offers higher power density (a smaller footprint) and more charge/discharge cycles, and vendors claim lower total cost of ownership despite a higher first cost.

These claims are vendor statements and the article offers no independent verification. Before retrofitting Li-ion into an existing UPS, one should confirm that the UPS charging circuit and controls support the chemistry, and carry out a cost-benefit study and a small pilot. The article dates from 2019, so standards and field experience that emerged later need to be assessed separately. NFPA 855 and UL 9540A are named as related standards.

Key points

1. Typical UPS battery duty is rare transfers with worst-case autonomy around 15 minutes.
2. Thermal runaway is usually caused by a charger that fails to reduce current, or by physical damage to the battery.
3. The author advises keeping Li-ion out of the data hall and in purpose-built battery rooms until failure modes are better understood.
4. VLA/VRLA strings are replaced at about 80% of original capacity; Li-ion degrades gradually and predictably.
5. Li-ion offers higher power density and more cycles; vendors claim lower TCO despite higher first cost.
6. Before a retrofit, confirm the charging circuit and controls support the chemistry, and do a cost-benefit study and a small pilot.
7. Related standards: NFPA 855, UL 9540A.

Using it in design

• Catalogue battery chemistry per UPS with an approved-location field (battery room versus data hall) and charger compatibility flags.
• Warn if Li-ion cabinets are placed inside the white space without a separate fire-rated room.
• Warn when a Li-ion retrofit is drawn on a UPS model not listed as Li-ion compatible.
• Assess battery room fire protection and ventilation separately for Li-ion, using NFPA 855 and UL 9540A as references.
• Ask for a cost-benefit comparison that checks vendor TCO claims against project data.

Who should read it

Electrical engineers and operations leads selecting UPS battery technology and designing battery room layout and fire protection.

Related standards

• NFPA 855
• UL 9540A

Publication details

Authors

Chris Brown

Publisher

Uptime Institute Journal

Year

2019

Document language

English

Source type

Industry body

Access

Free to read

Licence

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

Citation