The world of the automotive industry is changing rapidly, and terms that only yesterday seemed to be the domain of engineers are now becoming part of the everyday conversation of car enthusiasts. One of these concepts is a sequential hybrid, the operating scheme of which is radically different from conventional internal combustion engines. Unlike traditional cars, where fuel is burned in cylinders to directly rotate the wheels, here this process is converted into electrical energy.
To put it as simply as possible, in such a system internal combustion engine acts as a generator, not a traction force. It charges the battery, which in turn powers the electric motors mounted directly on the wheels. This allows the car to run solely on electricity, even when the gasoline engine is running.
This architecture opens up unique opportunities for optimizing fuel consumption and reducing harmful emissions. The driver no longer has to worry about finding a charging station, as is the case with pure electric cars, because the gasoline unit acts as an autonomous power plant on board. This solution is ideal for those who want to feel the dynamics of an electric ship, but are not yet ready to completely abandon liquid fuel.
Many people confuse a series circuit with a parallel circuit, where the internal combustion engine and electric motor can work together to accelerate. In our case, the connection between the wheels and the gasoline engine is completely mechanically broken. Electric motor is the only element that transmits torque to the road surface, which makes movement smoother and more predictable.
Operating principle of a sequential circuit
The basic principle of operation is based on an energy conversion chain: the chemical energy of the fuel is converted into mechanical energy, then into electrical energy and again into mechanical energy to rotate the wheels. It would seem, why such difficulties and loss of price? The answer lies in the efficiency of the engine itself. The internal combustion engine operates in a narrow speed range, where it Maximum efficiency, or doesn't work at all.
In a traditional car, the engine is forced to adapt to any conditions, from idling at a traffic light to suddenly accelerating when overtaking. In a series hybrid the situation is different. The combustion engine only turns on when the battery charge level drops below a certain threshold. It starts at optimal speed, produces current and turns off.
The Myth of Direct Connection
There is a common misconception that at high speeds the wheels are still connected directly to the internal combustion engine. In a purely sequential circuit this never happens, even on the highway. The entire energy path passes through an electrical circuit, which ensures stable performance in any conditions.
Electrical energy can go in two ways: directly to the motor wheels or to a buffer battery to accumulate excess. Inverter plays a key role here, managing the power flow between the generator, battery and traction motor. It is the electronics that decide when to charge the battery and when to give all the power to overclocking.
It is important to note that this design allows the use of smaller engines without loss of dynamics. Since the internal combustion engine is not rigidly connected to the wheels, its power is calculated based on the average need of the car, and peak loads are taken over by electric battery and an electric motor.
Key differences from parallel hybrids
To better understand the essence of the technology, it is necessary to draw a clear line between series and parallel circuits. In parallel hybrids such as many models Toyota or Hyundai, the internal combustion engine can directly drive the wheels through the gearbox. The electric motor acts as an assistant here, connecting when accelerating or driving at low speeds.
In a series circuit, often called electrical transmission, such a connection is completely absent. The wheels are always turned only by electricity. This fundamental difference determines how you drive and how your car behaves on the road. The absence of a mechanical link eliminates the need for a complex transmission with multiple gears.
- 🚗 Mechanical link: in parallel hybrids it is present, in serial hybrids it is completely absent.
- ⚡ The role of the internal combustion engine: in parallel it pulls the wheels, in serial it only charges the battery.
- 📉 Fuel consumption: in the city, a sequential scheme is often more efficient, since the internal combustion engine does not operate in inefficient modes.
Parallel systems benefit on the track, where the combustion engine operates optimally at all times. Sequential ones dominate in the urban “start-stop” cycle, where the possibility of energy recovery and operation on pure electricity provides tangible savings. The choice of architecture depends on the conditions for which a specific car model is being created.
Benefits of E-Power Architecture
Why do automakers such as Nissan with their technology e-POWER, are they betting on this particular scheme? The main advantage is the feeling of driving an electric car without “range anxiety.” The driver enjoys the instant torque of an electric motor and a smooth ride without shift jerkiness.
The absence of a complex gearbox (Gearbox) greatly simplifies the design of the transmission. There is no need for a torque converter, planetary gears or variators in their classical sense. This reduces the weight of the units and reduces the number of rubbing parts that are subject to wear. The mechanical reliability of such a system is potentially higher.
⚠️ Warning: Although the transmission is simple, the energy management system (BMS) and high-voltage battery require skilled maintenance. Do not attempt to repair power electronics yourself without proper approval.
Another important advantage is the possibility of using a smaller internal combustion engine. Because the engine operates in a constant, optimal state, engineers can tune it for maximum efficiency without having to worry about how it will behave when the throttle is opened suddenly. This leads to a reduction in noise and vibration levels in the cabin, since the engine does not change speed randomly depending on the speed of the car.
The main advantage of a sequential hybrid is the combination of the dynamics of an electric car and the autonomy of a gasoline car without the need for external charging.
Disadvantages and limitations of technology
Despite the obvious advantages, the sequential circuit also has its weaknesses, which should not be forgotten. The main disadvantage lies in the laws of physics: every energy transformation is accompanied by losses. The fuel is burned, rotates the generator, produces current, which charges the battery or goes to the motor, which turns the wheels. On the highway at high speeds, such a chain is less effective than direct transmission of torque from the internal combustion engine.
The high cost of components also plays a role. The presence of a powerful traction electric motor, an inverter and a buffer battery makes the production of such cars more expensive. Although the internal combustion engine is small, the total cost of the power plant may be higher than that of a conventional car of a comparable class.
- 📉 Efficiency on the track: When driving at a constant high speed, the consumption may be higher than that of a diesel or parallel hybrid.
- 💰 Price: complex electronics and batteries increase the final cost of the car.
- 🔋 Battery life: The buffer battery experiences constant charge-discharge cycles, which requires high-quality thermal management.
Additionally, at high speeds, the engine may be louder than expected. Since it is not connected to the wheels, its speed does not depend on the speed of the car. When accelerating hard on the highway, the internal combustion engine can reach high speeds to produce enough energy, creating a “rubber band” effect when the engine sound does not coincide with acceleration.
Comparison of system characteristics
To clearly understand the differences, you should refer to the comparison table. It will help organize information and see where each type of hybrid performs best. Numbers and parameters may vary depending on the specific model, but the general trends remain.
| Parameter | Series hybrid | Parallel hybrid | Series hybrid |
|---|---|---|---|
| Connection between internal combustion engine and wheels | Missing | Yes (via checkpoint) | Missing |
| Main engine | Electric | ICE + Electric | Electric |
| Consumption in the city | Low | Medium | Low |
| Consumption on the highway | Medium/High | Low | Medium/High |
| Transmission complexity | Low | High | Low |
The table shows that the sequential scheme wins in the simplicity of transmitting torque to the wheels, but loses in versatility over long distances. However, modern systems are becoming increasingly intelligent, minimizing these disadvantages through precise control algorithms.
Examples of cars with a sequential circuit
The most famous example of the mass adoption of this technology is the line of cars Nissan with e-POWER system. Models like Nissan Note or Nissan Qashqai with this drive became bestsellers in Japan and Europe. They have a small 1.2 or 1.5 liter petrol engine, which exclusively charges the battery.
Also a prominent representative is BMW i3 REx (Range Extender). In this model, the electric motor is more powerful, and the 650 cubic centimeter internal combustion engine serves only as an emergency generator to increase the range. When the charge of the main battery drops, the two-cylinder engine turns on, allowing you to drive another hundred kilometers.
☑️ Signs of a serial hybrid
Chinese manufacturers are also actively developing this area. Brands like Ideal (Li Auto) create large crossovers where the internal combustion engine acts as a generator, providing energy for powerful electric motors. This makes it possible to create very dynamic and heavy vehicles with fuel consumption comparable to compact sedans.
Prospects and future development
The future of serial hybrids looks vague but interesting. On the one hand, the development of charging station infrastructure makes plug-in hybrids and pure electric cars more relevant. On the other hand, for markets where charging is not available, the series circuit remains the ideal transition link.
Engineers are working to improve the efficiency of generators and reduce losses in the electrical circuit. The emergence of new types of batteries with high current output will make it possible to use internal combustion engines even less frequently. Perhaps in the future we will see hybrids where the internal combustion engine will only work 10-15% of the time, solely to maintain a minimum charge.
⚠️ Attention: When purchasing a used series hybrid, be sure to check the health of the high-voltage battery. Replacing it can cost up to 50% of the cost of the car, making the purchase unprofitable.
Technology Vehicle-to-Load (V2L), which allows the car to be used as a socket for household appliances, is implemented most naturally in series hybrids. Since the car already has a powerful generator and inverter, such cars often become mobile power plants for camping or working in the field.
If you are planning to buy a sequential hybrid for country trips, keep in mind that on long uphill climbs, fuel consumption may increase, as the internal combustion engine will work at its limit to charge the battery.
In conclusion, it is worth saying that a sequential hybrid is not just a compromise, but a separate philosophy of building a car. It combines the best features of both worlds, offering the driver the comfort of an electric car and the independence of a gasoline car. Understanding how this system works will help you make informed choices when purchasing your next vehicle.
Do I need to charge a series hybrid from a wall outlet?
No, classic series hybrids (like the Nissan e-POWER) do not have a plug-in charging port. All electricity is generated by an onboard generator. Plug-in versions exist, but they are less common and require a network connection to realize their full potential.
What happens if the battery runs out?
In a series hybrid, the battery cannot go to zero by design. The system will automatically start the internal combustion engine to recharge the buffer battery long before the energy reserve becomes critical for movement.
Is it possible to tow such a car?
Towing a series hybrid with running wheels on a cable is often prohibited by the instructions, since rotation of the wheels can generate current in the electric motors and damage the inverter when the system is turned off. It is recommended to use a tow truck.
Does the engine stall at traffic lights?
The internal combustion engine in a sequential hybrid stalls at traffic lights and in traffic jams, since at this moment the car moves solely on battery power. The internal combustion engine starts only when recharging is necessary.