One of the first things a new REEV driver may notice is that the petrol engine can sometimes start even though there is still charge left in the battery.
That does not necessarily mean the battery is low or something is wrong.
A Range-Extended Electric Vehicle manages its battery, electric motors and petrol-powered range extender as one system. The vehicle decides when running the generator makes sense based on how much energy is available and how much power is needed.
Here is what is actually happening.
The Petrol Engine Is Not the Main Drive Source
In a REEV, the electric motors are responsible for driving the vehicle.
The petrol engine has a different job. It works mainly as a range extender, generating electricity that supports the battery and electric drivetrain when required.
So when you hear the engine start, the vehicle has not suddenly changed into a normal petrol car.
The wheels are still being driven electrically.
If you want a more detailed explanation of the system, read our guide to how an iCAUR REEV works.
Why Can the Engine Start Before the Battery Is Empty?
A REEV normally does not wait until the battery reaches 0% before using the range extender.
Keeping some energy available in the battery helps the vehicle maintain consistent electric performance.
The engine may therefore start when the vehicle decides additional energy would be useful.
Common situations can include:
| Situation | What the REEV May Do |
|---|---|
| Battery charge becomes lower | Start the range extender to generate electricity |
| Strong acceleration or higher power demand | Use the generator to support available electrical energy |
| Long-distance driving | Manage battery and petrol energy together |
| Different driving modes | Adjust when and how the range extender operates |
The exact behaviour depends on the vehicle, selected mode and driving conditions.
Higher Power Demand Can Change How the System Operates
Imagine joining a fast highway or accelerating strongly to overtake.
The electric motors may suddenly require considerably more energy than they did while cruising through city traffic.
The vehicle’s energy-management system can respond by bringing the range extender into operation when additional electrical support is useful.
From the driver’s point of view, acceleration still comes from the electric motors.
This is one of the important differences between a REEV and a conventional petrol SUV.
Long Highway Drives Can Also Trigger the Range Extender
During short city journeys, a charged REEV may spend much of its time using stored battery energy.
Long-distance motorway driving is different.
Maintaining highway speeds for an extended period requires a continuous supply of energy. Instead of simply using the battery until it is nearly empty, the system can manage the battery and range extender together.
This is particularly useful for UAE driving, where a normal journey can quickly turn into a longer trip between Dubai, Abu Dhabi, Sharjah or other emirates.
You still have the option to plug in and recharge, but the petrol-powered generator means you do not need to stop immediately when the initial battery charge becomes lower.
Does This Mean the REEV Is Using Petrol?
Yes.
Whenever the range-extender engine is operating, it uses petrol to generate electricity.
That is why regularly charging a REEV still matters.
If you begin most everyday journeys with useful battery charge, more of your normal commuting can be completed using electricity stored in the battery. The range extender can then be kept mainly for longer journeys or situations where additional energy is required.
This is generally the best way to take advantage of the electric-first nature of a REEV.
Can the Driver Control When the Engine Starts?
To some extent, depending on the vehicle.
REEVs can offer different energy-management or driving modes that change how battery energy and the range extender are used.
However, the vehicle still manages much of the process automatically.
You should not normally need to watch the battery percentage and manually decide exactly when the engine should start.
The system is designed to manage that in the background while you drive.
For example, the iCAUR V27 REEV combines electric propulsion with a petrol-powered range extender, allowing it to manage stored battery energy and generated electricity across everyday and longer-distance driving.
Should You Worry When You Hear the Engine?
Usually, no.
Hearing the engine start during a journey can be completely normal in a REEV.
What matters is whether the vehicle is operating normally and whether there are any warning messages or unusual symptoms.
If the engine starts while the battery still shows some remaining charge, that alone does not indicate a fault. The vehicle may simply be managing its available energy according to the current journey.
The Bottom Line
A REEV does not need to completely empty its battery before starting the petrol range extender.
The system may use the engine earlier to generate electricity, support higher power demand or manage energy during longer journeys.
The important distinction is that the electric motors still drive the vehicle. The petrol engine is there mainly to supply additional electrical energy when needed.
For the driver, there is usually very little to manage.
Charge the vehicle when convenient, keep petrol available for the range extender, and let the energy-management system decide how to use both during the journey.
