Super Capicitors have been 10 years away for 40 years. It might happen, but really hasn’t yet.
Many experimenters have replaced car batteries with a deck of super capacitors that take up less than half the space and can weigh as little as one third of a conventional battery. Also, they tolerate temperature extremes better than most battery types. I built one for about $40.00 and also built a backup deck that fits in one of the pockets in the rear of my van. Fantastic money-saving device!