How Internet-Connected Batteries Caused Worldwide Grid Sags

For years, grid operators across the globe tracked a perplexing electrical anomaly. Every 60 seconds without fail, power grids experienced a sudden, minute frequency drop. This strange rhythmic sag appeared simultaneously across countries and continents, from Europe and the United States to Australia and Malaysia. While power grid frequency fluctuations are normal occurrences, the absolute clockwork regularity of these events caused deep concern among utility operators who feared cumulative stresses could eventually trigger destabilizing blackouts or damage critical generation equipment.

The puzzle finally found a resolution thanks to investigative and modeling work led by Dirk Witthaut and his research team at Forschungszentrum Jülich in Germany. Brought in by Germany’s largest transmission system operator, Tennet Germany, the researchers spent years analyzing data to track down the source of these ultra-low frequency oscillations. The discovery points not to heavy industrial machinery or renewable energy swings, but to the quiet, synchronized digital housekeeping of modern internet-connected power systems.

Tracking Down the 60-Second Pulse

Initial suspicions fell on traditional heavy infrastructure. Hydropower plants have historically driven ultra-low frequency oscillations (UFLOs) because vibrating turbines can hit resonant frequencies that magnify mechanical energy into electrical sags. Witthaut and his team tested this hypothesis using a computer model of a hydropower control system on the Scandinavian grid. While they replicated 60-second resonance peaks, mechanical systems naturally drift and fade, failing to explain why the electrical drop persisted with absolute clockwork precision every single minute.

Realizing that absolute regularity requires an absolute clock, the team shifted investigation strategies. They deployed more than 80 smart power quality meters across the Jülich campus, sampling medium- and low-voltage distribution lines, solar panels, and battery energy storage systems. The monitoring equipment soon recorded the exact same minute-by-minute frequency peaks on transformers attached to battery energy storage units. Further investigation in Ireland—where rapid data center expansion pushed these facilities to account for 18% of the national load by 2022—revealed that frequency drops quadrupled from 3 milli-Hertz (mHz) in 2016 to 12 mHz by 2021, with some recent spikes exceeding 20 mHz.

The Mechanics of Power Oscillation in Modern Inverters

To fully grasp how digital assets impact physical electrical transmission, engineers analyze the interaction between power electronics and AC grid frequency stability. Electrical grids operate on a strict balance between power generation and consumption. When load exceeds generation, frequency drops; when generation exceeds load, frequency rises. Traditional synchronous generators possess massive rotating physical mass, providing inherent inertia that resists sudden frequency shifts.

Modern power systems increasingly rely on inverter-based resources, including solar photovoltaics, wind turbines, and battery energy storage systems (BESS). These devices utilize complex Pulse Width Modulation (PWM) inverters rather than spinning turbines. While inverter technology offers rapid response times, it also introduces systemic vulnerabilities related to software scheduling. Network Time Protocol (NTP) synchronization ensures that distributed digital infrastructure maintains microsecond-accurate timekeeping across thousands of distinct physical locations.

When commercial uninterruptible power supplies (UPS) or utility-scale lithium-ion battery banks execute internal diagnostic cycles, their embedded microcontrollers draw a momentary pulse of active power. Because thousands of these independent units synchronize their internal clocks via NTP servers, their diagnostic algorithms trigger simultaneously. The resulting aggregate power draw acts as a square-wave impulse injected directly into the transmission network, creating the observed ultra-low frequency oscillations.

Impact on Data Centers and Industrial Fleets

The discovery of synchronized micro-draws carries broad implications for enterprise data center operators, original equipment manufacturers (OEMs), and utility providers. Hyperscale operators including Amazon Web Services, Microsoft Azure, and Google Cloud manage sprawling server farms equipped with massive arrays of lithium-ion and lead-acid UPS units. Under standard firmware configurations, these backup systems execute routine health diagnostics at identical intervals across global regional clusters.

Industry benchmarks reveal that a typical 100-megawatt data center can induce measurable voltage and frequency ripple across local distribution networks during simultaneous battery diagnostic cycles. Regional grid operators in densely populated tech hubs—such as Northern Virginia, Dublin, and Frankfurt—must now collaborate directly with data center developers to audit firmware settings. Power purchase agreements (PPAs) and grid interconnection rules are increasingly incorporating clauses that mandate randomized firmware configurations for large-scale power electronics.

A Decade of Detective Work

The timeline of this discovery spans nearly a decade of detective work across multiple academic institutions and transmission system operators:

• 2015–2016: Grid operators in Central Europe first notice persistent ultra-low frequency oscillations occurring at exact 60-second intervals. Initial anomalies measured around 3 mHz.
• 2018–2020: Data center buildouts accelerate sharply in Ireland and Northern Europe. Researchers note that oscillation amplitudes scale proportionally with regional data center energy consumption, rising past 10 mHz.
• 2021–2024: Forschungszentrum Jülich, commissioned by Tennet Germany, deploys high-density smart meter arrays to isolate distribution-level transformers, ultimately linking the sags to battery state-of-charge checks.
• 2025–2026: Industry groups publish comprehensive findings, prompting international standards organizations to propose firmware patch guidelines for connected power electronics.
• 2027 and Beyond (Projected): Regulatory bodies move toward mandatory compliance frameworks requiring randomized jitter algorithms in all newly manufactured commercial UPS and grid-tied energy storage units.

Frequently Asked Questions

What causes the minute-by-minute frequency drops on power grids?

The frequency drops are caused by fleets of internet-connected uninterruptible power supplies (UPS) and commercial battery storage systems checking their state-of-charge at the exact same time every 60 seconds, creating an aggregated electrical disturbance.

Are these frequency drops dangerous for the electrical grid?

While individual drops of 10 to 20 mHz are generally within safety limits for grids built to handle swings up to 200 mHz, they reduce safety margins and could compound with other grid stresses to trigger blackouts or equipment damage.

How can this coordinated grid disturbance be fixed?

Manufacturers can easily resolve the issue by issuing software patches that introduce randomized timing or staggered schedules for battery diagnostic checks, eliminating synchronized power draws.

Do smart home devices contribute to this problem?

Yes. Researchers found that various IoT devices and connected smart appliances also exhibit periodic power fluctuations, though widespread patching remains a challenge since only a tiny fraction of IoT hardware runs updated firmware.

Sources and further reading

Read the original reporting on TechCrunch.