What happened
- TechCrunch published on November 8, 2026 a story by Tim De Chant on how researchers solved a power-grid mystery: the frequency dips slightly every 60 seconds, and at the same moment on grids across countries and continents.
- Dirk Witthaut, of Forschungszentrum Jülich in Germany, took the case when Tennet Germany, the country’s largest transmission operator, brought him the puzzle. Solving it took years of investigative and modeling work.
- They first checked hydropower plants, which have historically caused ultra-low-frequency oscillations. The model found conditions that explained a peak once per minute, but not why it repeated without pause.
Why it matters
A grid’s operation depends on keeping the frequency within a range. If oscillations grow or operators do not know the cause and respond wrongly, blackouts can follow. Even without a blackout, the dips can damage power-plant equipment, especially hydropower turbines, if left unchecked.
That the origin is internet-connected batteries with almost perfectly synchronized clocks turns the case into a coordination problem among thousands of independent machines.
The number
3 mHz in 2016, 12 mHz in 2021. In Ireland, where data centers represented 18% of grid load in 2022, the minute-by-minute drop quadrupled between those years, and some recent drops exceed 20 mHz. The 50 Hz grid is built to withstand swings of plus or minus 200 mHz, and the operator would rather limit them to 100 mHz.
Context
If the cause was a clock, it had to be found. The team installed more than 80 power-quality meters around the Jülich campus, sampling frequency, voltage, current and power every three seconds. The transformer attached to the battery system peaked every minute, just like on the larger grids.
The explanation: many stationary batteries, from data-center UPS units to grid-scale ones, check their state of charge every minute. Because they are internet-connected, their clocks are almost perfectly synchronized. A single check goes unnoticed, but thousands together show. The researchers also found periodic fluctuations in internet-of-things devices, such as a smart oven and Raspberry Pi clusters.
The fix is simple: manufacturers add randomness to the checking schedule. For IoT devices a patch would suffice, but a recent study found that less than 3% run the latest firmware. TechCrunch adds that regulators may demand changes, though they only control their corner of the grid.
At Mamífero we have seen the growing role of batteries on the grid. Puerto Rico used Sunrun home batteries for 18 straight days, Genesis opened a 100 MW, 200 MWh battery in Huntly, Viridi installed a 3.75 MWh battery inside an occupied building and Rondo and Rio Tinto are designing a 360 MWh heat battery.
What’s next
- UPS and grid-battery manufacturers would need to randomize the charge check.
- Regulators could require it, but the problem is global and will need coordination among countries.
- TechCrunch warns that the mystery is solved but the problem could remain for years.
Bottom line
A harmless engineering practice, checking the charge every minute, becomes a risk when thousands of devices share it. The fix is minimal, and the real obstacle is getting it applied across so many different devices and countries.
Sources
- TechCrunch (Tim De Chant), “Coordinated disturbances haunt grids worldwide. Here’s how researchers solved the mystery.”, November 8, 2026, link.
- Cover image: Novoklimov, CC BY 4.0, via Wikimedia Commons
Edited by Rodrigo Cornejo. How we select and verify: who writes these notes.
