Design Notes

arranged based on the Spear energy module, which uses a rectangular pouch cell from LG Chem.

“Each module has 64-amp hours, which makes it roughly 21 times the size of the cell that’s in a cell phone. We take two of those and put them in parallel, and then take 24 and put them in series. That produces a module that has 11.3 kWh of embedded energy. That’s an 11-kWh unit, and it has a 100-volt maximum voltage,” Diller said. “We then take that module and put it in series with other modules to get to the system voltage that’s desired to work with the propulsion system. In this case, the drives want their voltage range to operate somewhere between 640 volts and 420 volts. So, I go with seven modules in series to get to a maximum voltage of 100 volts.”

From a safety standpoint, Diller said that there’s a battery management system to stop the electrical abuse of the battery. It prevents operators from doing the things that will cause a battery to catch on fire: overcharging it, charging it too fast, charging it when it’s frozen, or charging it after it’s been depleted to a 0% state of charge.

Charging and propulsion

The Maid of the Mist boats set o from a downstream landing to head toward the base of Niagara Falls daily, serving more than 1 million guests each year. While the ferry is docked and passengers are embarking and disembarking, the new boats’ lithiumion batteries are partially recharged. The seven-minute charge provides a battery boost enabling the vessel’s dual electric propulsion motors to maintain their total output of 400 kW (563 hp). Each trip consumes about 38 kWh. The batteries still have 80% power at the end of the working day.

According to Esteban Guerrero, master electrician for Maid of the Mist Corp., they have two charging stations.

The company uses a daytime charging station, and a nighttime charging station. The nighttime charging station is a trickle charge, with about 30-40 volts. The one the company uses during the day has a high output of 600 amps that charges the unit within seven minutes.

There are two motors operating L drive 360° directional thrusters in the stern (rear) of the boat (for propulsion), and there are two bow thrusters in the front that help with directional control. The result is a very maneuverable craft.

The old boats used a common straight shaft diesel design for the rear propeller. Kyle Taylor, one of the Maid of the Mist captains, explained that if you were to simply convert that setup to electric, but using the same basic transmission and components, the result would be much less e cient. So instead, the team decided to go with azimuth drives operating a propeller underneath the water. “It just made total sense for what we were doing here,” said Taylor.

Taylor said that the rear thrusters use L drives manufactured by Veth Propulsion (a division of Twin Disc, Inc.) and that maximizing lifespan and minimizing downtime are key concerns of Maid of the Mist Corp.

“These L drives have a super-low profile and are easy to maintain,” Taylor said. “We’re spoiled for space here, so we can crawl all around them. The goal is to have a warehouse full of spare motor drives and all the other components to minimize downtime. Our Veth drives are about 250-hp equivalents; there’s one per side, a 200-kW electric motor that we run at a maximum 80% output. So, it’s the same as the batteries — we don’t really charge above that or use components above that. We just try to get a long lifespan out of things.”

Even more green ABB is supporting e-mobility for applications outside the maritime world as well — for example, with public and private EV charging solutions. By early 2019, more than 10,000 ABB DC fast chargers had been sold in 73 countries. Looking ahead, products such as the company’s Terra HP high-power charger are designed to accommodate the higher-capacity batteries of tomorrow. Additionally, ABB is helping stakeholders across the globe establish electric bus services that reduce human impact on the environment.

The company launched its first DC fast charger in 2010, the first nationwide DC charging networks in 2012, and the first eBus charging networks in Europe in 2016. DW

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