Why is battery-only propulsion hard for ocean-going ships?

Battery-only propulsion is hard for ocean-going ships because batteries store far less energy per unit of weight than diesel or alternative fuels, so a battery pack sized for an ocean crossing would take up cargo space and add weight that cuts into what the ship can carry. This is the constraint Voltic's patented system is built to get around, using supplemental solar generation well beyond deck area rather than relying on battery capacity alone.

A cargo ship on a long ocean route needs power for days or weeks between ports. Matching that with batteries means carrying enough cells to cover the full voyage, since there is nowhere at sea to recharge. The result is a battery bank large enough to displace cargo volume, cut into deadweight capacity, or both, which is why battery-only container ships to date have mostly served short coastal or river routes rather than long ocean crossings.

Charging infrastructure compounds the problem. A ship that depends entirely on shoreside charging needs high-power charging available at every port it calls on, which most ports do not yet have for vessel-scale loads.

Voltic's approach addresses the range limit by adding solar generation capacity far beyond what deck space allows, producing power while under way instead of relying solely on a fixed battery charge. The company's patent covers this as an unlimited-range configuration, aimed specifically at the range and weight tradeoff that limits battery-only designs. The system attaches to an existing ship without replacing legacy infrastructure.