There is a new hybrid diesel that saves $60,000 per day in fuel consumption- its a new drill ship. I was at a place that builds power systems and they built this one that regenerates power from the anchor system that tethers a ship in place over a drill.
They had banks of large capacitors in a panel the size of a very large refrigerator, each capacitor was about 4 or 5 inches square and about 3 ft long I'd guess.
They used banks of lithium batteries, not ion though, and they could be drained and recharged quickly. They build systems for hybrid tugs, instead of running 4 large diesels all the time, mostly at part power, they run one diesel at full power and use electric motors as needed. Huge payback from fuel saving.
The advances in battery technology will get us to full electric with the range of a diesel and the ability to recharge quickly, plus half the weight of current batteries. I'm thinking maybe in the next 10 years. No more sensors or oil changes.