Charge for extra weight in train.

Dear Andrea,
You don't need to pay for the extra charge cause no one will actually check your luggage, so you can take all your luggage in the carriage.
If you want to consign your luggage, you need to get to the railway station a few hours early before departure (high-speed or bullet types do not accept luggage consignment), the fare is charged upon the weight of your luggage and also the distance of your trip.