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Battery self-tests synced to the minute cause grid frequency dips

Battery self-tests synced to the minute cause grid frequency dips

Built World

A Jülich-led team found the 60-second wobble in 12 grids on five continents and traced it to battery software that checks in at the top of every minute

October 30th, 2026: Study pins the wobble on synchronized battery checks

Overview

Updated Oct 31

A Jülich-led study found the one-minute dip in 12 of the power grids it examined, on five continents, including continental Europe, Britain, Korea, Australia and both main US interconnections. The cause is battery backup units that test their power supply at the top of every minute, with clocks set over the internet.

One manufacturer has released a software update that removed the strict one-minute pattern in one battery block the team studied, though its self-tests still run at set times. Witthaut's group wants the checks spread randomly. Ireland's one-minute signal quadrupled between 2016 and 2021 as data-centre batteries multiplied.

Why it matters

Every battery backup that self-tests on the minute adds to a grid wobble that wears on turbines. Randomizing the timing costs little.

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Key Indicators

60 s
Period of the grid wobble
Frequency records show a narrow peak at exactly one minute, about 0.0167 hertz.
12
Electricity systems measured
Frequency records from grids on five continents showed the same one-minute peak, including Iceland, Malaysia, South Africa and Mallorca.
80
Metering points on the Jülich campus
Building-level measurements traced the pattern to battery-backed uninterruptible power supplies.
22%
Irish electricity used by data centres, 2024
Data centres took 22% of measured electricity consumption in Ireland in 2024, up from 18% in 2022.
4×
Growth of Ireland's one-minute signal, 2016 to 2021
The amplitude of the signal quadrupled in five years.

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People Involved

DW
Dirk Witthaut
Head of the Department of Networks and Complex Systems, Institute for Energy Systems Engineering, Forschungszentrum Jülich
Lead researcher on the Nature Energy study; available for comment

Organizations Involved

Forschungszentrum Jülich
Forschungszentrum Jülich
National research centre
Led the study, with the University of Cologne and Karlsruhe Institute of Technology; the one-minute pattern appeared in 12 grids on five continents

German research centre whose campus doubles as a living laboratory for energy systems.
TenneT TSO GmbH
TenneT TSO GmbH
Transmission system operator
Recorded the recurring 60-second frequency dip over several years

Grid operator whose multi-year frequency records first made the one-minute pattern visible.
LL
Living Lab Energy Campus
Research infrastructure
Provided the building-level measurements that identified the source

Jülich campus testbed where energy systems are developed and measured in operating buildings.

Timeline

2020 October 2026

3 events Latest: October 30th, 2026 · 1 week ago

  1. Study pins the wobble on synchronized battery checks

    Latest Research

    A Jülich-led team reports in Nature Energy that battery systems querying their charge at the top of each minute produce the recurring dip, and calls for randomized timing.

  2. Ireland's one-minute signal quadruples

    Measurement

    Between 2016 and 2021, the amplitude of the one-minute frequency signal in Ireland grew fourfold as data-centre battery storage expanded.

  3. One-minute signal hits record levels in Britain and Scandinavia

    Measurement

    Grid records show the one-minute dip growing in intensity from about 2015, with record amplitudes in Britain and Scandinavia in 2020.

Scenarios

1

Battery makers randomize self-test timing

Possible Resolves by End of 2027

Discussed by: Dirk Witthaut and co-authors, who call for randomized scheduling in Nature Energy

Witthaut's group says the fix is to spread the checks randomly rather than start them all at the same moment. A software update to one battery block in the study reduced the strict periodicity but left some synchronization in place, so a full fix depends on vendors changing defaults across product lines, not on one patch.

2

Standards bodies set a rule for self-test timing

Uncertain Resolves by Q2 2028

Discussed by: Grid engineering analysts at gridperspective.com, who note the study's call for adaptive timing offsets

No binding standard governs these battery checks, which is why manufacturers independently settled on 60 seconds and the start of the minute. A requirement from an EU grid-code body or an international standards organization could mandate offsets or randomization. Slower than vendor action, but harder to reverse.

3

Storage growth outpaces any fix

Possible Resolves by End of 2028

Discussed by: Witthaut and co-authors, who warn the problem could grow with storage expansion

If defaults stay and nothing is standardized, each new battery installation adds to the synchronized load step. Ireland's experience is the template: the signal quadrupled in five years as data-centre batteries multiplied. The same trajectory in other markets would mean more wear on hydro turbines and other equipment.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

December 1999 - January 2000

Y2K date rollover (1999-2000)

As the calendar turned to 2000, computer systems worldwide were scheduled to evaluate dates written with two-digit years. Companies and governments spent years auditing code and running tests, because a shared clock would make many independent systems act at once.

Then

Few serious failures materialized, and the rollover passed with scattered, limited disruptions.

Now

The episode made clear how much infrastructure depends on synchronized time, and it established practices for testing clock-driven software before a deadline.

Why this matters now

Both cases turn on the same mechanism: a shared clock causing many separate machines to act simultaneously, with consequences that only appear at the system level.

June 2012

Leap second outage (2012)

An extra second was added to Coordinated Universal Time on 30 June 2012. A flaw in how some Linux systems handled the adjustment caused servers to hang, and several high-traffic websites reported outages.

Then

Service disruptions lasted hours at some sites; vendors issued patches.

Now

Companies began auditing how their software handled clock adjustments, and the leap second stayed contentious for years.

Why this matters now

A one-second change to a shared reference clock knocked out systems that were individually well built. The 60-second grid wobble comes from the same kind of coupling.

Sources

(10)
+4
Forschungszentrum Jülich Nature Energy Mirage News Grid Perspective iXBT heise online Chosun Biz Universität zu Köln Karlsruhe Institute of Technology Nature Energy