The 2005 Toyota Prius has a standard lead acid battery for operating the lights and other equipment, and a large battery pack that operates the electrical motor. The standard lead acid battery is the one most often replaced; it requires only 500 to 600 cold cranking amps, and its price is pretty much standard. The main battery pack, which will last the life of the car in most cases, has a high replacement cost.
Open the trunk and remove the spare tire cover located under the floor mat, as well as the side cover, located to the right of it -- just lift them out. Remove the air duct running from the main motor battery on the left, and the intake duct, located just to the left of the auxiliary battery. Use a socket to remove the bolt on the side of the duct, as well as the two bolts from where it is attached under the package tray.
Remove the negative battery terminal from the battery located on the passenger's side of the trunk, using a socket. Remove the battery hold-down clamp, using a socket -- there are two bolts in the rear-facing side of the bracket and one in the front-top side.
Pull off the red plastic cover over the positive terminal. Remove the positive terminal, using a wrench. Leave the large secondary cable attached, and swing the whole unit toward the rear, so it is out of the way.
Remove the old battery and install the new one. Install the positive terminal with the secondary cable attached. Install the battery hold-down bracket. Install the negative battery terminal. Install the air duct. Replace the cover over the battery and the one over the spare tire. Pull the carpet over the covers.
