Eurobat’s annual event in Brussels got a lesson in no-nonsense Yorkshire frankness when retired consulting engineer Ian Bitterlin took to the podium to discuss European data-centre UPS, writes James Snodgrass
In June this year Eurobat, the association of European automotive and industrial battery manufacturers, held its annual event in Brussels. Amid the sober talks on market trends and battery innovation, an interloper from academia challenged the battery industry on its assumptions about datacentre UPS and its fanciful notions on recycling.
Ian Bitterlin, professor emeritus at the University of Leeds – and retired chartered engineer – used his Eurobat presentation to challenge the way European data centres specify uninterruptible power supply (UPS) batteries. His central contention was that the industry has allowed batteries to become commoditised, routinely buying on price rather than engineering each system for its actual duty.
He began by distinguishing between AI training and inference. The gigawatt-scale facilities required to train large language models, he argued, were unlikely to be built in Europe because of grid constraints, regulation and carbon targets. European growth would instead be driven largely by inference: the distributed use of trained AI models in urban and edge data centres.
Invoking John Ruskin, Bitterlin reduced his purchasing philosophy to a simple rule: “You get what you pay for.” Yet, he said, an industry that describes itself as critical infrastructure often installs the cheapest available batteries. “The UPS industry always calls itself critical … and then it goes and buys cheap, shitty batteries in China. There’s no excuse.”
Bitterlin’s most forceful argument concerned autonomy. Data-centre batteries are commonly specified for 10 or 15 minutes, although the IT load may be lost far sooner if cooling is unavailable. A standby generator can start and accept load in about 11 seconds, he said, while the cooling plant may require another minute to recover. The battery’s real task is therefore to bridge roughly 75 seconds between grid failure and the restoration of electrical power and cooling.
“If you put in 15 minutes, you’re paying for 13 minutes’ worth of rubbish,” he said. The extra capacity cannot protect an IT load that has already shut down through rising temperature. Moreover, UPS systems are designed for full load but normally operate well below it, often with redundancy. Peukert’s law means a nominal 15-minute battery may provide considerably longer at its actual load. Bitterlin therefore urged suppliers to explain the duty honestly, reduce autonomy and spend the saving on a better battery rather than merely cutting capital cost.
That approach, he argued, favours high-rate lead batteries, including thin-plate pure-lead designs capable of delivering very high power for one or two minutes. Weight and energy density, decisive in drones, portable electronics and EVs, offer little value in a stationary data centre. A well-designed VRLA battery can provide eight to 10 years of service on float, he said, whereas cheap automotive-style 12V blocks may fail after three or four years.
He attacked the marketing sequence that follows such failures. UPS suppliers first reduce battery quality to protect their margins, then present lithium-ion as the remedy by comparing its claimed 15-year life with a low-cost lead battery replaced every three years. “If you start with a decent battery … it makes the lithium-ion battery still look really expensive,” he said.
Bitterlin also rejected the description of VRLA products as sealed or maintenance-free. They are valve-regulated and can release hydrogen during recharge, requiring ventilation. Conversely, lithium-ion requires a battery-management system because abnormal charging or cell reversal can initiate thermal runaway. Its principal safety disadvantage, he said, was that a fire could not readily be extinguished because the reaction generated its own heat, fuel and oxygen. Referring to FM guidance, he advocated keeping lithium-ion batteries outside the building envelope in fire-rated, adequately separated enclosures. “You can’t extinguish the battery. End of story.”
His most contentious remarks concerned sustainability. Bitterlin praised lead as a mature, extensively recycled material while dismissing claims that lithium-ion batteries could be recycled at rates approaching 97%. Such figures may refer to the battery’s total weight, he argued, while lithium itself forms only a small fraction of that weight and is commonly left in black mass rather than economically recovered.
“You can recycle everything else, but you can’t recycle the lithium,” he said, describing practical lithium recovery as a fantasy. He also questioned the mining footprint, transport requirements and Europe’s dependence on Chinese cell and drivetrain manufacturing. For stationary UPS, he argued, importing a lighter, more energy-dense chemistry brought little functional benefit while creating additional fire-protection, monitoring and end-of-life costs.
His conclusion was not that lead should be used everywhere. Lithium-ion was appropriate where low weight, compact dimensions, temperature range or repeated cycling justified it. His point was that data centres require a different optimisation. “Design every battery according to the duty,” he said. For the European UPS market, that meant challenging inherited 10- and 15-minute specifications, educating customers about the real operating load, and designing a high-quality battery system around the approximately 75 seconds for which it was genuinely needed.
