The battery in an electric car is huge — often several times the capacity of a home storage battery. For most of its life that battery just sits in a driveway doing nothing. Bidirectional charging is the idea that it should not. A 2022 Enel X Way patent shows the hardware that makes a car's battery flow both ways.

Ordinary charging is one-directional: grid power flows into the car. Bidirectional charging adds the reverse path — the car can push power back out, into your home during an outage (vehicle-to-home) or onto the grid when it is stressed and prices are high (vehicle-to-grid). The mechanism requires power electronics that can run in both directions and, critically, that can do so safely and in sync with the grid's voltage and frequency.

“High power bidirectional charging systems with a split battery architecture are disclosed. The bidirectional charging systems can include a bidirectional charger and an integrated battery.”— U.S. Patent No. 11,498,448 source

Enel X Way's grant US11498448B2, "High power bidirectional grid connected charger with split battery architecture," tackles the high-power version of this. The 'split battery' detail is the interesting engineering: dividing the system lets it handle high power flows in both directions more flexibly. The charger is no longer a one-way funnel; it is a two-way interface between a giant mobile battery and the grid.

Why the arithmetic is staggering: a single EV might store enough to run a house for a day or two. Multiply by millions of vehicles, most of them parked at any given moment, and the parked fleet becomes one of the largest potential storage resources imaginable — capacity that already exists, bought and paid for as transportation. Bidirectional charging is the key that unlocks it.

The honest brakes: two-way charging stresses the battery, raising warranty and degradation questions; it requires utility approval and interconnection rules that are still maturing; and it needs the car, the charger, and the grid operator to all speak the same protocol. A 2022 patent on the charger hardware is one necessary piece, not the whole system. But it is the piece that proves the physical interface is buildable — the rest is contracts and software.