What’s an ultracapacitor? Tesla’s clever acquisition explained

Perhaps it got stepped on by the seemingly unusual news that

Volkswagen’s

Electrify America will be

installing Tesla Powerpack battery systems

at its charging stations, but the announcement that

Tesla is acquiring Maxwell Technologies

, a developer and producer of ultracapacitors, is far more significant. It not only will put

Tesla

products into a number of other automakers’ vehicles, but it further extends the company’s capabilities and capacities in electrification, both mobile and static.

So what is an

ultracapacitor

? It can simply be thought of in the context of a “burst.” As in a sudden burst of energy. In a battery, there is a chemical reaction going on inside; in an ultracapacitor, the energy is stored in an electric field. There is a positive charge on one side and a negative charge on the other, and the two are kept apart by a separator until needed — and then the opposites attract, pronto.

Another benefit of storing the charge in a field is that the ultracapacitor can be recharged many more times than a battery.

An example of this need for a burst of power is in automotive start-stop applications, where ultracaps are being used, with Maxwell, for example, supplying

General Motors

and PSA.

Think of a battery as something that takes a comparatively long time to discharge and then recharge (which is the case for your phone as it is for a car). This is not the case with ultracaps. So while a battery is appropriate for powering a car over the long run, an ultracapacitor provides more of a transient push.

One way that ultracaps can be recharged in a vehicle is through regenerative braking, wherein the kinetic energy of braking is captured and used to generate electricity that is then stored in the ultracap. This is something that

Lamborghini

is doing with Maxwell technology.

Another use of an ultracapacitor in a vehicle is to take care of peak transient load requirements. When the battery system alone just can’t get it done, then the ultracap can kick in to handle the electrical demand.

Last year, for example, Zhejiang Geely Holding Group announced a technology partnership with Maxwell. (Geely owns

Volvo

, which, as you’ll remember, has announced that it is putting an electric motor into every

new vehicle

it launches starting this year and plans to have 50 percent of its sales fully electric by 2025.)

Qingfeng Feng, vice president and CTO of Geely, said, “The Maxwell ultracapacitor subsystem has proven to provide significant support for our

hybrid cars

and will be able to economically handle the challenging peak power demands in a way that batteries alone cannot.”

In this context, it is worth noting that one of Maxwell’s markets is for power smoothing on utility grids, and Tesla has a business of providing energy storage for everything from municipalities to homes, so this ultracap tech is relevant there, too.

As for Tesla’s vehicles? Perhaps the ultracapacitors will give rise to some sort of Ultra-Ludicrous mode.