NOVELTY - The system (2) has a closed compartment (4) of batteries containing electrochemical cells (20) i.e. lithium-ion cells. The compartment comprises a pipe (6) that emerges towards outside of a car e.g. hybrid car. The pipe allows entry of water under pressure in the compartment. The pipe comprises a normally closed obstruction system (22) that is able to open automatically according to particular external conditions relative to fire in the compartment. An end (8) of pipe comprises a red colored visual location unit.    USE - Battery system for car e.g. hybrid or electric car (all claimed). Can also be used for battery system comprising cells that eject flammable liquids.    ADVANTAGE - The pipe comprises the normally closed obstruction system that is able to open automatically according to particular external conditions relative to fire in the compartment, thus protecting the compartment by avoiding accidental water input. The pipe is short and is of low mass, thus allowing economic manufacturing of the battery system, and reducing fuel consumption of the vehicle. The pipe provides limited pressure loss for water flows. The obstruction system is simple, economic and is of low mass, thus improving safety of the vehicle. The end of the pipe comprises the red colored visual location unit, thus allowing the pipe to be easily identified by first-aid workers during fire control. The compartment is easily accessible from lower part of the vehicle for exchange or maintenance actions. The relatively important mass of the compartment is provided at low height, thus allowing to sufficiently maintain a low center of gravity for the vehicle, and hence ensuring a large and easy access to the boot.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a hybrid or electric car.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic top view of a battery system.    Battery system (2)    Closed compartment (4)    Pipe (6)    End of pipe (8)    Electrochemical cells (20)    Normally closed obstruction system (22)