Electric vehicles and the 12V battery

The term hybrid only means that there is more than one energy source for the operation of the vehicle. In fact, vehicles with Start-Stop technology are already considered "micro-hybrid" vehicles, because here the 12V battery acts as a second energy source when the engine is switched off.

The evolution of the "micro-hybrid" was the so-called "mild-hybrid", in which a 48V Li-ion battery is installed to supply particularly energy-hungry consumers. Although these two systems are already called hybrids, they lack a crucial feature that has long been associated with "hybrid electric cars": Purely electric driving without the aid of the combustion engine.

The difference between Full Hybrid and Plug-in Hybrid Vehicles

The term "Hybrid Electric Vehicle" actually describes two different concepts. The "Full Hybrid Electric Vehicle" (FHEV, usually abbreviated to HEV) and the "Plug-in Hybrid Vehicle" (PHEV). Both approaches share the fact that the vehicles have a high-voltage lithium-ion battery and can thus be driven purely electric.

The difference between the two systems lies in the charging strategy for the high-voltage battery. In an HEV, the battery can be charged exclusively by the combustion engine or by brake energy recovery (recuperation). In a PHEV, the battery can also be charged at a charging station, as in a purely Electric Vehicle, hence the term "Plug-in". Due to the limited charging possibilities, the capacity of the drive battery in an HEV is generally smaller than in a PHEV. Due to the lower capacity of the battery, the distances that can be covered purely electrically are also shorter for an HEV than for a PHEV.

PHEV body, with smaller fuel tank but larger battery with external charging port for longer electric range.

Both systems enable purely electric and thus local emission-free driving. Thanks to the additional combustion engine, the vehicle can also be used for long distances without restrictions. If the combustion engine is not used, a hybrid electric vehicle behaves like an all-electric car.

Pros and cons of HEVs and PHEVs

Today, all signs point to electric drive systems as the propulsion system of the future. However, it is not yet clear which energy storage system will prevail. The development of lithium-ion battery technology and fuel cells is currently highly dynamic, so that enormous progress is currently being made in both areas. In addition to technical innovations, both areas are concerned with scalability and cost reduction in production.

The focus of technical developments in traction batteries continues to be an increase in energy density. The aim is to make the batteries smaller and lighter while maintaining the same capacity, i.e., the same driving distance of the vehicle. At the same time, efforts are being made to optimise the chemical composition of the battery cells to reduce the percentage of critical metals, such as cobalt to a minimum.

Even though there are already some hydrogen-powered cars on the market, the mass production of fuel cell drives is still further away than that of lithium-ion batteries. Current development is focused on reducing the need for platinum in the fuel cell to significantly lower costs. Further progress is being made in making the fuel cell membrane more robust and durable.

Apart from the energy storage system, the powertrain architecture of Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs) is largely comparable.

1. 12 Volt Battery
2. DC/DC Converter
3. Large high-voltage LiIon battery
4. AC/DC Converter
5. High-voltage traction motor
6. Electrical power source (charging station/wall box)

The FCEV uses a hydrogen tank, a fuel cell, and a small Li-ion battery as intermediate storage to power the electric drive.

1. 12 Volt Battery
2. DC/DC Converter
3. Large high-voltage LiIon battery
4. AC/DC Converter
5. High-voltage traction motor
6. Fuel cell
7. Hydrogen tank

Pros and Cons of BEVs and FCEVs

• Less complex drivetrain than HEVs, thus potentially lower maintenance costs
• High torque and good driving dynamics through pure electric drive
• Local emission-free driving
• With BEV: Low operating costs in connection with a private photovoltaic system

• Less extensive network of hydrogen fuelling stations and charging stations compared to conventional petrol stations
• Long "refuelling" for BEVs
• Many models only partially suitable for long-distance use
• Without subsidies, more expensive than comparable conventional vehicles with combustion engines

The low-voltage system in every Electric Vehicle

Conclusion