Honda 1997 Civic Sedan Online Reference Owner's Manual page 146

If the terminals are severely cor-
roded, clean them with baking soda
and water. Then use a wrench to
loosen and remove the cables from
the terminals. Always disconnect the
negative ( — ) cable first and recon-
nect it last. Clean the battery termi-
nals with a terminal cleaning tool or
wire brush. Reconnect and tighten
the cables, then coat the terminals
with grease.
If you need to connect the battery to
a charger, disconnect both cables to
prevent damage to the car's electri-
cal system.
The battery gives off explosive
hydrogen gas during normal
operation.
A spark or flame can cause the
battery to explode with enough
force to kill or seriously hurt you.
Wear protective clothing and a
face shield, or have a skilled
mechanic do the battery
maintenance.
NOTICE
Charging the battery with the cables
connected can seriously damage your
car's electronic controls. Detach the
battery cables before connecting the
battery to a charger.
Maintenance
Battery