At 170Wh per kg (and ignoring the weight of the containers and any safety considerations), 20GWh of lithium battery would weigh 120,000 tons. This is a lot more

At 170Wh per kg (and ignoring the weight of the containers and any safety considerations), 20GWh of lithium battery would weigh 120,000 tons. This is a lot more than a typical Panamax DWT of 60,000 tons, which also needs to include the ship's fuel, provisions, crew, etc.