There regenerative braking is a braking system used on all electric and hybrid vehicles, full hybrid or plug-in, during slowdowns. On this subject there is an interesting technical novelty which guarantees the continuity of the descent operation even when the battery is 100% charged with e-Pedal effect always guaranteed!
How regenerative braking works and its benefits
There regenerative braking is activated when the driver releases the accelerator pedal (or presses the brake pedal), with the electric motors acting as current generators by converting thekinetic energy into electrical energy which is stored in the traction battery to be used to accelerate and move the vehicle.
Offers different advantagesthe first is to recover some energy usually dissipated into heat, thus increasing theenergy efficiency overall of the vehicle and at the same time guaranteeing a greater autonomy in electric mode. The second advantage is that it saves traditional brakes by extending the life of discs and pads.
Regenerative braking problems when the battery is 100% charged
who uses aelectric car or full hybrid on mountain trails on descents he is used to intensively using regenerative braking to slow the car down. And if the car has the option of regulating its intensity, perhaps on multiple values, using the paddles on the steering wheel, fun going down a mountain is guaranteed. Regenerative braking can be increased to slow down near tighter bends or hairpin bends by pulling the paddle, usually the right one, while pulling the left one releases the brakes and the car picks up speed.
After several kilometers faced downhill, regenerative braking can go into crisis. This occurs when the battery is fully charged. Indeed in electric or hybrid vehicles the regenerative braking system comes first reduced and then deactivated completely when the battery reaches its maximum charge level, i.e. reaches 100%. This was designed to avoid overloading of the traction battery and to protect the system.
But this can be a problem for those who are driving downhill, especially when approaching a bend or hairpin bend: the moment they pull the right paddle to increase braking, they suddenly find themselves without the brakes.
This OFF of the regenerative braking occurs in advance, already within the first 10 km of descent, on hybrid cars with more limited capacity batteries such as full-hybrid (1.7-3 kWh), after a greater mileage for plug hybrids -in (10-15 kWh) and even higher for electric cars with much larger batteries above 20 kWh.
It is also true that the problem could immediately arise for an owner of an electric or plug-in car leaves the house after recharging the car and tackles a descent with 100% battery. In this case, to slow down, you can only refer to the traditional braking system, which is based on mechanical brakes.
Regenerative braking, Renault’s “infinite” effect
Renault is among the first manufacturers to tackle this problem, solving it very well and with a very simple technical solution.
The precious intervention of Renault which guarantees a regenerative braking ongoingwe found it during the test of the new Austral Alpine, more powerful version, subjected to numerous tests on routes including mountain with steep downhill sections and gradients of 300/500 meters, such as those to descend from the highest point of the mountain ( 1,000 meters asl) towards the Turano lake (550 meters above sea level), from Collalto Sabino (980 meters above sea level) towards via Turanense (600 meters asl) or to get off the village of Rock of Cave (933 meters asl) a Quarries (400 meters above sea level).
Regenerative braking, the long downhill test
L’Austral full hybrid it has a 2 kWh battery (1.7 kWh usable) which is easily recharged when going downhill and can reach 100% in just 4/5 km. During the test on the steepest descents, I made extensive use of the paddles on the steering wheel, varying the intensity of the regenerative braking, to slow down and re-accelerate the Austral without ever touching the brake or accelerator pedal. I carefully monitored the battery charge status because nearing 100% I was already preparing myself for the sudden absence of the electric brake which would have abandoned me at any moment. Among other things, the regenerative braking of theAustralwhen set to maximum, is very strong: arriving near a hairpin bend and suddenly finding yourself with the car as if it were in neutral with no brakes could cause apprehension.
Regenerative braking always active
As I continued downhill, using the paddles on the steering wheel, I noticed that the regenerative braking was always active, never giving up. How is it possible? Maybe they put an additional electrical resistance to dissipate the electric current produced downhill? Technically possible, but that would be sheer madness. So I thought that Renault’s brilliant engineers had taken the problem head on and found the solution? But how?
Renault’s technical solution for always active regenerative braking
At this point the doubt occurred to me that the car was slowing down as usual but using the traditional brakes without me acting on the brake pedal. Cool! This is technically possible today because many cars (such as the Austral) have an electrified master cylinder which can therefore be controlled via software. At the end of the descent, for the avoidance of doubt, I slowed down the car as much as possible without touching the brake pedal and, once stopped, I went to check the temperature of the front brake discs.
Well, discovered the mystery! The disks, generous among other things on the Austral, were piping hot.
Indeed, the Austral continues to guarantee braking downhill when passing, in a very fluid and almost imperceptible way (apart from a warned tap), from electrical to mechanical using the traditional brake system with the definitive cancellation of the surprise effect caused by the sudden deactivation of the regenerative (electric) braking, a problem existing on all electric, hybrid and plug-in cars when the battery reaches 100% charge.
My compliments to the French technicians and engineers at Renault for spotting a very important technical solution for the safety of those who use electric or hybrid cars on long mountain descents.
In our numerous tests we had already pointed out and highlighted this shortcoming of regenerative braking with a 100% charged battery, see the video below.
Thanks to this technical solution from Renault, there is a continuous regenerative braking effect without interruptions and without surprises even on the longest and most demanding descents. Long live the e-Pedal!
However, if you notice amalfunction in the regenerative braking system when the battery is not fully charged, there may be a problem or malfunction in the system. In this case, I advise you to contact the manufacturer’s assistance service to subject your car’s system to a careful diagnosis.
Keep following us, a very interesting test on the most powerful Austral, the Alpine, is coming soon, also on video!
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