If you are making the move to convert your gasoline powered car into an electric car, you will need to have a secure battery box to store your batteries in.  Depending on the number of batteries you will have in your new electric car, most of them will be located in the rear section of the passenger compartment.

The purpose of an electric car battery box is to prevent fumes from entering the passenger compartment when the batteries are charging and to protect occupants of the car in an accident. The box also keeps the batteries warm in cold weather. There is usually limited space in the front of the car which is why an electric car battery box is stored in the rear of the vehicle.

If you are constructing your own electric car battery box, you need to make it large enough to hold most of your batteries comfortably.  Mounted on the side should be an explosion proof brushless fan that ventilates the box when the batteries are charging. The fan is wired in series with the fan in the battery charger so when the charger is on the battery box fan is on. A marine grade ventilation bilge hose is attached to the fan and routed to the vent on the underside of the car.

The battery box for your electric car should be constructed of marine grade plywood and painted with water repellant paint. Metal banding needs to be secured around the box so the weight of the batteries will not break the box apart in an accident.
The electric car battery box will then be securely mounted with bolts to the frame of the car. For ease of installation the box should fit into the trunk.  However, with careful planning, some cutting, and a little welding, the electric car battery box can be sunk into the floor of the trunk to regain storage space. Before the batteries are installed, a layer of baking soda should be spread on the floor of the box and the air bags in the coil springs need to be filled with air.
If you are undertaking your own conversion from a gasoline car to an electric car, building the battery box for your electric car needs to have special attention paid to it.  This is where your power will be coming from, and you need to be sure that nothing happens to it.