While electric car manufacturer Nio doesn’t yet have the global presence of some of its rivals, it does have something that none of its competitors have right now: battery swapping technology.

Tesla toyed with the idea of battery swapping technology back in 2013, claiming it could swap out the battery of the Model S in just 90 seconds. However, the automaker soon abandoned the idea, opting instead to stick with its Supercharging network. In China, Nio has gone all-in on battery swapping and in a recent Twitter post, revealed that its owners have completed over four million battery swaps across the country.

Read More: NIO Unveils Next-Generation Battery Swap Station, First Established In Beijing

Nio’s announcement comes just six months after it revealed its owners had completed more than two million battery swaps. The automaker currently has 504 Power Swap stations that are operational.

Using a battery swap station from Nio couldn’t be simpler, as the video from Fully Charged below shows. All you do is jump on the Nio smartphone application and find a Power Swap station nearby. The app will tell you how many fully charged batteries are available at that station and how many vehicles are waiting to have their batteries swapped.

Once the driver arrives, a Nio employee reverses their vehicle in to the station. The car is then hoisted up and the system removes the screws holding in the battery. The battery is then taken below ground and dropped off at an area where it is recharged. A new battery pack is then automatically installed.

The process takes just three minutes and is free for owners of new Nio models. Those that own used Nio models are charged based on how many kilowatt-hours of energy they need from their new battery pack. For example, if they pull up with an old battery with a 20 per cent charge (20 kWh), they will pay the going rate for the extra 80 kWh needed for a fully-charged 100 kWh battery from the automaker, which can cost as little as $10.