A voice from the darkness. Will there be mobile communication in the event of a total blackout?

Ukrainian mobile operators have undergone several stress tests during the full-scale war. While in 2022–2023 they were only learning to operate during power outages, by 2024, autonomous network operation for 10 hours without electricity became a mandatory requirement from the regulator.

Today, when there may be no electricity for ten hours in Kyiv and other regions, mobile communication is mostly maintained, albeit with interruptions. But will this margin of safety be enough in the event of a total blackout?

From two to ten hours of battery life

The first massive attacks on the energy sector in the winter of 2022/2023 showed that the backup power for base stations was nominal. The old batteries, which the stations were equipped with before the war, provided communication for a maximum of one to two hours in the absence of electricity until a repair crew arrived, he says. LIGA.net Oleksandr Hlushchenko, former CEO of the OTT service Omega TV.

After the blackout in November 2022 Operators began replacing them with modern lithium-ion batteries. They can operate on a single charge for about four hours, Kyivstar and lifecell told us in 2024. But a new wave of the energy crisis has increased the demands on the endurance of uninterruptible power supplies.

In the summer of 2025, the National Center for Operational and Technical Management of Telecommunication Networks obliged mobile operators to ensure the autonomous operation of all their base stations for at least ten hours after a power outage.

The solution was lithium-iron-phosphate batteries. LiFePO4.

Such batteries have a lower capacity compared to lithium-ion batteries, but are better adapted to prolonged outages thanks to their greater durability. They have thirteen times more charging cycles, Vodafone told us. In the first half of 2024, the company ordered and installed 83,400 LiFePO4 batteries on its cell towers.

Another advantage, given the short power supply intervals, is that lithium-iron-phosphate batteries charge quickly. According to the lifecell press service, they need an average of three to four hours for a full charge. The company currently also uses LiFePO4.

Base stations with fully charged batteries can operate autonomously for up to 10 hours, according to the press services of Kyivstar and lifecell. Vodafone states six to eight hours or more, depending on the time of day and subscriber load.

When the batteries are discharged, the base stations are powered by generators. The most optimal tactic is to recharge the batteries themselves from the generators when their resource is reduced by half, says Oleksandr Hlushchenko. This way, the service life of both devices can be preserved.

Generators are primarily located at hub stations, which form the center of a cellular cluster of base stations. Mobile teams are dispatched to other locations as needed, according to lifecell. To know which area needs repairmen and when, the company's engineers monitor the status of each site online: charge level and load.

Why does the connection still disappear?

However, the duration of power outages is increasing faster than autonomy of the mobile network. If base stations can operate for 10 hours, then there is often no electricity for 20–30 hours.

In such cases, problems arise that worsen the quality of communication. During power outages, 60% of consumers switch from fixed to mobile internet, according to Vodafone. "This increases the load on the network by three to four times" – internet speed decreases, and batteries drain faster.

In addition, battery performance also deteriorates due to the weather. Just as in hot weather, batteries are less efficient in freezing temperatures: the current output from the battery to the base station decreases, and the voltage protection is triggered earlier, explains Tetiana Popova, head of the board of the Ukrainian Telecommunications Chamber. Moreover, she notes, a supercooled battery simply will not charge when electricity becomes available.

Lifecell batteries have an automatic self-heating function, which turns on when the temperature of the cells drops below approximately 10°C. However, this also requires electricity, which shortens the battery station's runtime.

As a result, the batteries don't have time to charge from the grid, and therefore fuel generators are beginning to play a key role in maintaining power at base stations, Vodafone notes.

Telecommunication operators have created a strategic fuel reserve and increased the number of generators. But in sub-zero weather, they also present difficulties: engine starting deteriorates, components wear out, and fuel consumption increases, according to Kyivstar. In December alone, they used over 1 million liters of fuel to power generators.

In early January, the maximum number of Kyivstar base stations in Kyiv and the region that were simultaneously operating on backup power reached 40%. Under such conditions, some base stations stop working. Neighboring stations can increase their power, says Popova, head of the board of the Telecommunications Chamber of Ukraine.

However, due to the increased load on them, the connection degrades: voice calls still "get through," but not 4G, she clarifies. In some locations, all mobile services may become temporarily unavailable.

How many subscribers lost their connection in January? Vodafone provided us with specific figures. Thanks to additional generators, the stability of their connection significantly improved in the first month of 2023 compared to December, the company assures. However, even so, during the longest outages, network availability dropped to 78% in Kyiv and 75% in the Kyiv region. Under normal circumstances, this figure should be 100%, the operator clarified.

What will happen in the event of a total blackout

In the event of a multi-day power outage, the mobile network breaks down into "islands" — connectivity is maintained only where there is electricity or generators are running.

"When a district in Kyiv is without centralized power for more than 30 hours, the base stations there also go down. Approximately as many people are left without electricity as are left without mobile service," explains Tetiana Popova.

So far, Kyiv has not lost power simultaneously in all districts. But how will mobile communication work if the entire city or most of it is de-energized for several days? After just one day, only voice calls will be available in some places, for example, to call emergency services, says Tetiana Popova. You can forget about the internet, she adds.

Without the internet, cashless payments in stores will become significantly more difficult – terminals operate on mobile internet, notes Oleksandr Hlushchenko. However, these devices have the ability to reserve transactions and defer them until a signal appears.

Regarding voice communication, it will not disappear in Kyiv under almost any circumstances, according to LIGA.net's sources. This is only possible in the event of a nationwide power outage and a complete loss of all fuel reserves, says Hlushchenko.

The operators' core network sites, on which the operation of the clusters depends, are primarily equipped with generators and have fuel reserves. In the event of prolonged blackouts, Kyivstar will ensure uninterrupted communication for at least three days for all critical network nodes, the company says.

In addition, base stations with backup power either are critical infrastructure themselves or are often located on such facilities. They are reserved to withstand power outages for four days or more, according to Vodafone.

In case of a mass power outage at base stations, a backup power scenario has been developed for each locality, covering priority facilities that will geographically cover the entire city, ensuring maximum coverage and operation of the transport network, the company adds.

"In such a scenario, users may experience a decrease in internet speed, but the connection will continue to work," Vodafone stated.

As long as key base stations can be powered by generators, it will be possible to get a signal in Kyiv, Hlushchenko is convinced. He cites the situation in Mariupol at the beginning of the full-scale invasion.

"In Mariupol, there was a Kyivstar base station in the city center, which worked (female) for a very long time, even during the siege. Because there were people who supported the generator's operation. And all these shocking photographs "They were sent from Mariupol via mobile internet," the expert recalls.