Honda 2003 Civic Hybrid Owner's Manual page 215

Battery
Check the condition of your car's 12
volt battery monthly. You should
check the color of the test indicator
window, and for corrosion on the
terminals.
216
Maintenance
TEST INDICATOR WINDOW
Check the battery condition by
looking at the test indicator window
on the battery.
The label on the battery explains the
test indicator's colors.
Check the battery terminals for
corrosion (a white or yellowish
powder). To remove it, cover the
terminals with a solution of baking
soda and water. It will bubble up and
turn brown. When this stops, wash it
off with plain water. Dry off the
battery with a cloth or paper towel.
Coat the terminals with grease to
help prevent future corrosion.
WARNING: Battery posts,
terminals and related accessories
contain lead and lead compounds.
Wash hands after handling.