A battery casing system for a traction battery in a motor vehicle, said battery casing system comprising a battery casing having a plastic battery casing shell which at least partially defines a battery casing volume for accommodating at least one battery component. The battery casing system of the invention is characterized in that same includes at least one reinforcing means which can be connected to an outer face of the battery casing shell and which is formed separately from the battery casing shell. The invention further relates to a traction battery comprising a battery casing system as well as to a motor vehicle comprising a traction battery.