Honda 1993 Civic Reference Owner's Manual page 120

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
reconnect it last. Clean the battery
terminals 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
electrical system.
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