The most recent episode of Fully Charged is about an electric ferry, which reportedly turns out to be the world's biggest electric ship conversion. It entered service in November 2018.
It's equipped with a massive 4.1 MWh battery (640 packs) and 6 MW of power (four 1.5 MW propellers) with a diesel engine onboard only for emergencies.
The ferry runs between Helsingborg in Sweden and Helsingor in Denmark - just around 4 km (2.5 miles), but it runs a lot - 46 crossings per 24 hours (184 km/114 miles) and up to 17,000 per year!
The energy consumption of the ship is beyond imagination as the 4.1 MWh pack would last only for 3.5 runs (14 km/8.7 miles). However, the crew makes sure that keep the state-of-charge within 40-66% of the battery capacity and there's a fast charger on each side of the trip so the battery will last longer. It's expected that the battery will survive some 5 years, maybe more, while the payback period is around 8 years (in the middle of the second battery's lifespan we assume).
The number of up to 17,000 partial-charges (85,000 over 5-years) doesn't tell the whole story as the charging is done at 10 kV and 600 A, which translate to some 6 MW.
The connection is fully automated and takes around 45 seconds. Then the ferry charges for usually nine minutes in Sweden and five minutes in Denmark.
Video Description via Fully Charged on YouTube:
100% Electric Ferry Crossing | Fully Charged 4k
One our recent Tesla Model 3 test drive we crossed from Denmark to Sweden on a 100% battery electric ferry. The 4 kilometre crossing between Helsingborg in Sweden and Helsingor in Denmark doesn't seem that far, but this ferry is crossing up to 46 times a day, and charging for a few minutes each side. The route handles more than 7 million passengers and almost 2 million vehicles each year with crossings every 15 minutes.