Powertrain Overview: Hydrogen Fuel Cell Vehicles

Since the creation of the first modern automobile nearly a century and a half ago, there has been one dominant engine option on the market, the gasoline internal combustion engine. Now the gasoline internal combustion engine has some challengers trying to steal the crown. There have been many different types of engines in the past but many of them relied solely on fossil fuels to operate.

Recently though, because of increasing fuel economy standards and emission awareness, a new breed of engines is emerging. Many of these are relying on electricity to aid in powering the vehicle. With these new power plants comes a new set of rules and warnings on how to repair them. A lot of collision technicians have an idea about how some of the new powertrains work, but not a full understanding of what is going on under the hood. It is important to understand the inner workings of the engine in order to safely and properly diagnose and repair them after a collision. In this series, we’ll walk you through many of the current engine options and how they convert the fuel they’re consuming into usable power. Let’s explore the hydrogen fuel cell electric vehicle (EV) powertrain.

Hydrogen fuel cell vehicles are a type of electric vehicle. The way that the vehicle moves is the same as other electric vehicles, but where the electricity comes from is a different story. The primary fuel is hydrogen (H2), with oxygen (O2) being the second piece of the fuel. The idea behind this powertrain is the hydrogen wants to combine with oxygen to create water whenever possible. However, just the act of the two elements combining isn’t enough to power a vehicle. Some barriers and special materials are required to make things turn, you may even have to look back at your high school chemistry days to fully understand.

Imagine hydrogen on one side of a barrier and oxygen on the other. The barrier in the middle only allows positively charge protons to pass over to the oxygen side. The hydrogen’s electrons however, are negatively charged. As a result, they can’t pass through the barrier. In order for the protons to pass through they have to lose the electrons. This is where a catalyst, normally platinum, is used. The catalyst separates the electrons and the positively charged hydrogen passes over to the oxygen side. The negatively charged electrons only have one way to meet back up with the hydrogen and oxygen, and that is by means of a wire going around the barrier. The electrons flowing through the wire creates electricity. This electricity is then used to power the electric vehicle motor. The electrons then flow over to the other side of the barrier where the meet up with the hydrogen and oxygen to create water or H2O. The water is the only emissions that are produced by the hydrogen fuel cell vehicle. This basically means the energy that powers the vehicle is from a chemical reaction, not from anything combusting like a traditional gas-powered engine.

While hydrogen is the most abundant element in the universe, it is also the most flammable element. This means that many special cautions need to be taken when repairing fuel cell vehicles. This can include draining down the hydrogen tank before bringing the vehicle into a repair facility or making sure the temperature doesn’t go above certain temperatures when baking paint. It is difficult to tell if hydrogen ignites because it burns as a colorless flame. With the possible explosion risk of the hydrogen tank, fuel cell vehicles normally have different shields and protections built into the vehicle to ensure the tank doesn’t get damaged. It is crucial to properly reinstall all components that protect the tank.

These vehicles have a 12 V battery to run accessories and a high-voltage (HV) battery to run the electric motor. Due to the high-voltage, it is extremely important to properly disable the battery before service is performed. The HV battery can cause serious injury or death if not handled properly. Make sure to consult the service information for proper disable procedure. Also, the 12 V battery will need to be disconnected and isolated when welding is performed so that damage does not occur.

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