At a distance, a fuel cell vehicle can look like a battery electric vehicle with an extra energy source. There is still a traction motor, an inverter, a high-voltage bus, a battery, a DC/DC converter, and a thermal system. The difference is that the main energy converter is not a battery pack. It is a chemical plant that happens to be bolted into a vehicle.
That changes the job of the control system. A BEV is mostly about managing stored energy. A fuel cell electric vehicle is about managing a live reaction while still meeting the driver's torque request smoothly.
The stack is not alone
The fuel cell stack gets the attention, but the surrounding balance-of-plant is where a lot of the interesting work lives. Air supply, hydrogen regulation, humidification, coolant flow, purge strategy, and electrical loading all affect whether the stack is efficient, durable, and responsive.
The compressor is a good example. It is not just an accessory load. It shapes oxygen availability, transient response, efficiency, and noise. If the driver asks for torque faster than the air path can support, the battery has to cover the gap while the fuel cell system catches up.
Why the battery still matters
An FCEV still needs a battery because the stack is not the right tool for every transient. The battery handles launch, regen, fast torque changes, and short bursts of high power. The stack can then operate in a calmer region where efficiency and durability are better.
From a controls view, the question is constantly: how much power should come from the stack right now, how much should come from the battery, and where should the state of charge be a minute from now?
The real architecture problem
The hard part is not drawing the boxes. The hard part is coordinating them. Thermal limits, humidity state, compressor speed, battery state of charge, driver demand, and diagnostic constraints all pull on each other.
That is what makes fuel cell powertrains interesting to me. They sit in the overlap between electrochemistry, controls, software, and vehicle behavior. You can model the system cleanly on paper, but the vehicle always reminds you that every subsystem has a voice.