Braking system in electric and hybrid cars.
Braking system in electric and hybrid carsToday's cars need to be more and more efficient, especially those with unconventional drives. To improve cars in this respect, the brakes in hybrid and electric vehicles are equipped with special energy recuperation
Today's cars need to be more and more efficient, especially those with unconventional drives. To improve cars in this respect, the brakes in hybrid and electric vehicles are equipped with special energy recuperation systems. It recovers the kinetic energy that the vehicle loses when braking.
Braking system in electric and hybrid cars
How does the braking energy recovery system work and how is it serviced?
When driving a car equipped with a regenerative braking system, the electric motor draws power from the traction batteries and drives the wheels. This creates kinetic energy, which – as we remember from physics – is produced by any object in motion.
When we press the brake pedal, the kinetic energy previously used to propel the vehicle through the wheels will activate the electric motor. It will act as a generator. It will not consume electricity, but will start generating it.
The resulting electricity is then stored in traction batteries, from where it is again taken to drive the car. It allows the engine to run for a longer distance and increases the range of the car. The more charged the traction batteries, the longer the distance can be covered by the vehicle. Regenerative braking converts the vehicle's kinetic energy into electricity.
One of the most popular braking energy recovery systems m.in is the KERS, which was once used in Formula 1 races (Kinetic Energy Recovery System). However, due to its enormous weight, it was an unnecessary ballast for single-seaters with conventional petrol engines used until 2013.
Since 2014, a hybrid drive has been installed in cars competing in the F1 world championship – equipped with the ERS system (recovering mechanical energy, which also includes kinetic energy). The MGU-K component is part of it, m.in. It operates at a temperature close to 500 degrees Celsius and converts the resulting heat energy into electricity.
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The principle of operation of the hydraulic braking system in electrified cars
The differences between combustion and electrified cars can only be between the models and the energy recovery systems used. This is influenced by the driver's system settings and weather conditions. The current condition of the car and the road surface also contribute to this (the more slippery or "treated" with salt and sand, the worse it is for the brakes). The speed of travel and the location in which we are are also important (the higher above sea level, the more rarefied the air is, and this affects the operation of the brakes).
With more frequent use of regenerative braking and less frequent support of the hydraulic system, damage to the final components of the system occurs in a different way. The brakes require even more attention here than in cars with conventional drives. They are used less frequently and the discs are more sensitive to tarnish on the friction surface. In the event of a slight tarnish, this can be removed by disabling the braking energy recovery system once in a while. Unfortunately, in many situations, a visit to the workshop cannot be done.
Choose your brake discs
Is the braking system in electrified cars long-lasting and does not require much attention?
Of course it is not. To avoid more frequent servicing, it is advisable to use measures to prevent this. Where we have the possibility to regulate the degree of recuperation, it is worth encouraging customers to drive a few kilometers without additional recovery from time to time – as mentioned above. We will then "clean" the brake discs and pads.
A good habit, not only in hybrid cars, is to make a few stronger brakes in the initial phase of driving – after installing new discs and pads – and to run these elements in.
In some cases, there is another problem, which is felt when driving faster for long periods of time. When the wiper sensor detects rain, the pads can be moved against the disc at pre-set intervals to clean the blade. Thus preparing the car for sudden braking with full efficiency. However, this will not be enough if, as a result of negligence or improper installation, a tarnish has already formed on the disc that cannot be wiped off with normal braking.
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What should you watch out for in hybrid and electric cars with regenerative braking?
In many cars, pressing both pedals (brake and accelerator) at the same time may result in the need for a mechanic to intervene earlier. You should not try to "clean" the tarnish on the discs by pressing both pedals at the same time. With a hybrid and an electric car, you have to brake a few times longer from time to time.
In this case, grease is also not a suitable preventive measure. It might seem that if we want to brake less often with a hybrid or electric car (where the brakes are rarely used anyway), it is enough to "lubricate better". Nothing could be further from the truth. Each brake system manufacturer specifies precisely which parts can be lubricated and which lubricant should be used. When it comes to regular maintenance, the "less is more" principle applies. Adding excess grease on individual components will not improve anything and may even harm the brakes.
What else should you watch out for when it comes to hybrid or electric cars?
The Toyota Prius is one of the most recognizable hybrid car in the world. In the second generation model, you can find the requirement to use DOT3 brake fluid.
This is an example of not necessarily constantly improving brake fluid. You should not replace it with a theoretically "better" DOT4, suggesting the possibility of replacing it every two years rather than every year. In the braking system of the Toyota and Lexus brands, we have many more actuators, solenoid valves and cylinders. Thicker DOT4 fluid will contribute to the malfunction of the braking system in these cars. However, it is important to remember that this is not a rule for all hybrid cars. In the case of BMW, the German manufacturer recommends the use of DOT4 fluid.
It is not important that the liquid is still the right color. If you really want your car to serve you well for many years, you should ensure that the fluid is changed regularly. Ideally, at least every 2 years. Then we enable him to work in a clean environment. The liquid also has an absorption and anti-corrosion effect. As if that wasn't enough, the depleted fluid significantly contributes to faster wear of the system lines and the master cylinder.
When it comes to choosing the chemicals used to service the braking system, we should be guided by the expertise and recommendations of the manufacturers. It is best to see what is written on the cap for the brake fluid reservoir. There, you should check the relevant properties by making sure of the records from the service book or the diagnostic computer.
Using the wrong fluid and the resulting swelling of the rubber components can have the same effect as braking too lightly or only regenerative braking. A locking brake may not "clean" the disc sufficiently. If blocked, it can, in turn, cause irreversible overheating.
When we talk about the braking system, there are no more or less important elements. A system designed to be reliable has as few of them as possible – therefore, each of them is very important. The entire system will only be as reliable as its most unreliable part. Let's keep that in mind.