How Does Regenerative Braking Work In Ebikes?
When it comes to picking an electric bike, there are so many different features and functions to consider. From the speed to the mileage to the battery charge time, there is seemingly no end to the number of different specs on the market, many of which can have a significant impact on the quality of your ride.
Well, regenerative breaking is just another aspect to add to the list. Although this feature is a common sight on modern day electric cars, it is seen less often when it comes to electric bikes.
But is regenerative braking the great energy-saving function which it’s lauded as, or is it just another marketing scam? Here’s a look at whether regenerative braking is worth taking into consideration when it comes to choosing your ebike.
What Is Regenerative Braking?
Regenerative braking is a system by which the electric motor on your bike is able to generate electricity from the kinetic energy that you output when you brake. Using the mass from the weight of the bike and the rider and the velocity from travelling, regenerative braking claims to preserve energy that would have otherwise been wasted. This energy can then be fed back into the battery, allowing it to be reused later. In theory, this means that you can increase your power and mileage per charge.
How Does It Work?
Usually, the energy that you build up as you increase your speed and momentum is wasted when you come to a halt. As the brake pads clamp the wheels, the friction is translated into heat and lost into the air. However, regenerative breaking allows you to store and reuse this energy.
This works by reversing the usual process of the electric power. Rather than energy from the battery flowing to the motor which in turn propels the wheels, when you brake, the power to the motor is cut and it begins to function more like a generator, feeding back the energy that you used when braking in order to produce electricity. This energy can flow back to the battery, adding charge.
How Much Energy Could You Save?
Regenerative braking is nowhere near as effective for bikes as it is for cars. Due to the lighter weight of a bike and the slower travel speeds when compared to a car, there is far less energy to be captured on a bike.
Although you can retain some energy through the use of regenerative breaking, tests show that this is minimal. Estimates place the amount of charge to be gained at between 2 and 20 per cent, although it is more likely to be at the lower end for most users, lying around 5 per cent. On a smooth, flat road with few stops, you are unlikely to capture enough energy to have any significant impact.
In addition, in order for the motor to double up as a generator, the regenerative braking mechanism requires it to be permanently engaged, meaning that you can actually end up losing rather than gaining energy as you lose the ability to coast. Furthermore, this means that when the battery runs out of charge the rider is still having to pedal against the resistance of the motor, making for a tough ride.
On top of this, ebikes with regenerative braking require a different type of motor to a standard ebike, called a ‘direct drive hub motor’. These are heavier than the usual motor, meaning that the bike is even more cumbersome than it would be anyway, which can also reduce the ability of the bike to travel long distances.
On the other hand, if you are anticipating a lot of very hilly terrain on your daily travels, then the accumulative energy could be slightly more significant. Nevertheless, in either scenario a lot of the energy from your bike’s battery is expended on combatting air resistance, meaning it is effectively rendered pointless in most situations.
Is It Worth It?
Considering all the points laid out above, the simple answer is no. General consensus across the board places regenerative braking firmly as marketing hype rather than a useful and desirable function to opt for on your ebike. It is considered to be more efficient to coast slowly at stopping points than to come to a direct halt with regenerative braking.
Generally speaking, regenerative braking is only really worth it for those travelling extremely regularly on steep hilly terrain whilst starting and stopping constantly, which is highly unrealistic for most users. Otherwise, it is likely to lose you more energy than it will save.
In reality there are other energy saving features that are far more likely to save you energy than regenerative braking and are far more worth spending your money on. As wind resistance is one of the main saps on your bike’s energy, even investing in some Lycra clothing and a streamlined helmet is likely to give you better gains!