The Prius is a gas and electric hybrid car manufactured by Toyota. It is the most fuel-efficient gas car in the U.S., according to the United State Environmental Protection Agency. In many respects, changing the 12 volt battery in a Prius is similar to any other 12 volt car battery, but accessing the battery in the Prius is not as simple as lifting the hood of a regular car.
Open the rear door of the Prius to access the 12 volt battery. Lift up the cover on the floor in the rear area. Remove the retaining screws using a screwdriver and then lift off the cover and place it to one side. You can see a well in the floor panel that the battery is in.
Disconnect the two battery cables from the Prius' 12 volt battery using a long handled adjustable wrench, since it is difficult to reach down to the terminals. Move the battery cables to one side.
Remove the nuts holding the metal clamp in place on the 12 volt battery using a wrench. Lift off the clamp. Use both hands to reach down into the well and then carefully lift the battery from the well.
Put your new 12 volt battery into position in the well. Gently lower it down until it is seated on the base area.
Put the metal clamps on the battery and replace the nuts, then tighten using a wrench. Try moving the battery to ensure it is securely held in place.
Reconnect the clamps on the end of the two battery cables onto the battery terminals. Tighten the clamps using a wrench. The red battery cables connect to the terminal label "+" and the black battery cable connects to the "-" terminal.
Replace the floor cover. Put the retaining screws back in the holes and tighten using a screwdriver. Close the rear door.
You will lose all your electrical settings when you disconnect the battery cables. You can reset them by referring to the user manual. Alternatively, connect a backup battery before disconnecting your existing battery. Use a small 12 volt battery. Attach a wire from the positive terminal of your back up battery to the clamp on the end of the red battery cable using a strip of insulating tape. Repeat the process using a strip of wire from the negative terminal of the backup battery to the clamp on the end of the black battery cable. When you disconnect the cables, electricity still flows to keep your settings. Remove the wires once you connect the new battery.