Gearbox for E-cars
One gear for all cases
Seven gears for the manual, twelve for the automatic. For a long time, carmakers and especially transmission manufacturers have concentrated on more and more gear ratios. In the electric car, on the other hand, a single-speed transmission is enough. This is how it works.
The electric car, as should be clear to everyone by now, is revolutionizing car manufacturing. Although manufacturers need new expertise in battery technology, the rest will be much simpler: An electric motor is many times simpler than a combustion engine. And transmission manufacturers are also facing change.
For many years, they have continued to refine their automatic and dual-clutch transmissions in particular, curbing thirst with up to twelve gears and making the gearshifts as comfortable and at the same time as sporty as possible. But all the brainpower, money and time that went into the development may soon be worthless. Because: electric cars usually get by with fairly simple single-speed transmissions.
Classic gasoline or diesel engines provide a large part of their power only in a certain speed range. In order to use this sensibly and, above all, economically, a transmission with different gears is needed that keeps the engine speed more or less constant. The electric motors are different: they deliver their power over an extremely wide range, so they develop similar torque at both low and high speeds. In theory, a rigid connection between the motor and the drive shaft would be sufficient for electric cars. In practice, however, an input gearbox is usually used as a so-called reduction gear, which reduces the speed of the motor by a fixed factor, usually about 1:10, thus making it manageable. For the driver, it feels like an automatic transmission; all he has to do is set it to "D" after starting the engine (for Drive) switch.
One gear is enough to get an electric car off to a brisk start and enables electric cars to reach higher speeds on the highway, even though they are usually only driven at speeds of up to around 140 km/h anyway. Above that, power consumption becomes excessively high, mainly due to air resistance. Some suppliers and manufacturers are trying to solve this problem with an automatic two-speed transmission, but the savings potential is in the single-digit percentage range. On the other hand, there are higher costs for the more complex transmission, which in the end would have to be borne by the customer – and at present the expensive electric cars can only be made palatable to the customer with heavy discounts anyway. That's why most carmakers leave it at the simpler one-speed solution.
Only in the case of electric-powered supercars like the Porsche Taycan does a two-speed transmission offer a real advantage: not in terms of fuel consumption, but in terms of top speed. With just one gear ratio, the electric sports car from Zuffenhausen would not reach 260 km/h. Here, however, money doesn't play such a big role either.