Can I Change My Own Battery on My 1999 BMW 328I?

1. Plug the battery backup tool into the cigarette lighter (auxiliary power outlet). This is just a small 9-volt battery attached to a plug suitable to plug into this outlet. It will supply just enough power to keep the circuits and memories alive.
2. Open the trunk and remove the battery cover on the right side of the trunk floor. Remove the battery negative terminal connector with the use of a wrench. Remove the battery positive terminal connector. Loosen and remove the battery hold-down clamp using a wrench. Disconnect the battery vent tube. Lift the battery out of the car.
3. Install the new battery and tighten the hold down clamp using a wrench. Install the vent tube to the nipple on the top side of the battery and make sure the hose passes through the hole in the floor. Install the positive battery cable connector on the positive terminal on the battery and tighten it with a wrench.
4. Install the battery negative cable to the negative terminal on the battery and tighten it with a wrench. Re-install the battery cover on the trunk floor. Unplug the battery backup.