Cadillac 2005 XLR Owner's Manual page 346

4. Open the hoods and locate the batteries. Find the
positive (+) and negative ( ) terminal locations on
each vehicle. See Engine Compartment Overview
on page 6-12 for more information on location.
CAUTION:
{
An electric fan can start up even when the
engine is not running and can injure you. Keep
hands, clothing and tools away from any
underhood electric fan.
6-38
CAUTION:
{
Using a match near a battery can cause battery
gas to explode. People have been hurt doing
this, and some have been blinded. Use a
flashlight if you need more light.
Be sure the battery has enough water. You do
not need to add water to the battery installed
in your new vehicle. But if a battery has filler
caps, be sure the right amount of fluid is there.
If it is low, add water to take care of that first.
If you do not, explosive gas could be present.
Battery fluid contains acid that can burn you.
Do not get it on you. If you accidentally get it
in your eyes or on your skin, flush the place
with water and get medical help immediately.