Executive Summary

• This is your guide to battery and energy storage for data centres, whether you need a refresh or learning about a sector of the industry you’re not familiar with.
• BESS is a hot topic right now in the industry as we increase resilience and create strict backup solutions in case facilities face unplanned outages.
• There are four types of batteries used in data centres: NMC (Lithium Nickel Manganese Cobalt), LFP (Lithium Iron Phosphate), Redox Flow and Sodium-Ion.

Data centres have complex IT infrastructure and there are times when the systems fail and there needs to be a backup solution in place to minimise disruption to the servers. This is where battery and energy storage enter the chat. This is a little guide, or a refresher, on the types of battery and energy storage there are out there.

What is BESS?

BESS, short for Battery Energy Storage System, is like a sponge, soaking up excess green electricity when there’s lots of it (and it’s cheap) and feeds it into the power grid when demand spikes. Wind turbines and solar panels only generate electricity when the weather feels like it, so there are times when we have huge mismatches in terms of demand and supply. There are four main battery types; not all of them are built the same. To get a better understanding of the type, what it is and why it’s great, here’s the breakdown:

The four types of battery

• NMC (Lithium Nickel Manganese Cobalt): This is your classic choice for traditional, space-constrained UPS (Uninterruptible Power Supply rooms. It has extreme energy density, which means if you need to pack maximum power into a small space, this is the only one that does the trick. However, the battery can become unstable at temperatures between 150 degrees and 210 degrees, so they need a robust cooling system to keep it safe and operational.
• LFP (Lithium Iron Phosphate): This is the data centre heavyweight champion for modern BESS. It has wonderful thermal stability at higher temperatures, is safe to put into modular blocks outdoors and can handle over 6,000 charge-discharge cycles. However, the drawback is that it’s 10 to 15% heavies and larger, so fitting this into facilities struggling for space is nigh impossible.
• Sodium-Ion (NA-Ion): 2026 is the year of the salt, literally. Its superpower is that it doesn’t need cobalt, lithium or any cooling. These are cheap, sustainable and immune to volatility, unlike a certain lithium we know. They also operate safely in extreme temperatures with a cooling system. Sounds good, however, it has lower energy density, so to get the same backup as a lithium battery, you need a larger physical footprint.
• Redox Flow Batteries: For longer backup consistently compared to diesel generators, this is the one. They don’t store energy in solid cells; it’s stored in giant external tanks of liquid electrolyte. These bad boys have zero cycle-driven degradation and can run for over 30 years. However, their drawback is very slow response times and with high-density AI workloads, the difference can be a matter of milliseconds. These batteries aren’t used for instant UPS backup, but for deployment alongside on-site renewables to keep servers running during prolonged outages.

Every battery type has its place and a recommended strategy would be to use a combination of them for facilities to ensure the more energy-dense systems can be used for those instant UPS scenarios, while others help with sustained outages.