In a recent article in Popular Mechanics, editor Mike Allen declared himself a fan of ultracapacitors for hybrid cars. He explains how he visited Honda's development facilities 15 years ago and found himself testing a mild hybrid that used an ultracapacitor to store energy. However, we all know that current hybrids don't use ultracapacitors. Instead, they have powerful batteries, which have a higher power density and a price that is going down.Nevertheless, Allen predicts that once ultracapacitors can be made successfully at a competitive price point, conventional hybrids will use them because of the "capacitor's longer life span and lower internal resistance, as well as its deep-discharge tolerance. While a battery pack can be damaged by being discharged completely, capacitors simply don't care." On the other hand, he foresees that plug-in hybrids will always need batteries for their main battery pack, while using capacitors to reclaim energy while slowing down and to provide high-current acceleration. EESTOR must be happy.
[Source: Popular Mechanics]