Unique Under the Floor: The Flat Hydrogen Tank That Replaces BMW's Battery

With a hydrogen car, attention usually goes to the fuel cell, but with the new BMW iX5 Hydrogen the real breakthrough lies elsewhere: in the way the hydrogen is stored. For this, BMW developed the Hydrogen Flat Storage System, a flat tank system the company says is unique in the car industry. Several patents have now been filed on it.

From round cylinders to a flat layout

Hydrogen tanks have traditionally been thick, round cylinders. They take up a lot of space and are hard to fit into a car really designed for a battery. So BMW chose a very different approach: seven slim tanks that together form a flat, compact unit. That flat design makes exceptionally efficient use of the available space and delivers a range of up to 750 km.

Seven tanks, one smart system

The tanks are so-called Type 4: a plastic inner liner fully wrapped in carbon fibre set in resin. That combination is light yet strong enough to hold hydrogen at a pressure of 700 bar. The seven tanks are connected in parallel and form a single sealed unit controlled by a central main valve. Together they store at least 7 kilograms of hydrogen — enough to refuel completely in under five minutes.

Fits exactly where the battery sits

The clever part is the placement. The flat tank unit takes up exactly the same underfloor space as the Gen6 battery pack in BMW's electric models — without sacrificing cabin space. That means the hydrogen version of the X5 can roll off the same production line as the electric, plug-in hybrid, petrol and diesel versions.

Why this is so special

Until now, hydrogen cars were often built separately and in small numbers, because their tanks did not fit a standard platform. BMW turns that around: because the tank sits where the battery goes, production can simply scale with demand instead of relying on a separate, costly line. That lowers complexity and cost, and makes it easier to add new technology later.

Safely packaged

The tanks sit protected within a robust metal frame, which together with the body provides extra protection in a collision. In this way BMW combines a high storage pressure with safe installation. Series production of the iX5 Hydrogen starts in 2028 at the plant in Steyr, Austria.

A solution that coexists

What is appealing about this approach is that hydrogen and battery-electric do not get in each other's way, but literally share the same space and the same factory. Both are zero-emission; the customer chooses what fits best. For those covering long distances who want to refuel quickly, this flat tank system shows just how practical hydrogen can be.

Sources

• BMW Group – "New BMW iX5 Hydrogen tank system" (2026)
• BMW Group Press – "Technology-open approach meets the art of engineering: the new hydrogen tank in the BMW iX5 Hydrogen"
• CompositesWorld – "BMW's patented flat storage system uses CFRP tanks for iX5 hydrogen"
• Autocar – "BMW solves hydrogen packaging puzzle"
• Electric & Hybrid Vehicle Technology International – "BMW's new hydrogen tank design delivers 750 km range for iX5"