Honda HSM1380i Owner's Manual page 44

Battery electrolyte level
Remove the rear cover (see page 92) and check whether the battery
electrolyte is between the upper and lower levels.
If the battery electrolyte is near or below the lower level, fill the
distilled water to the upper level.
UPPER LEVEL
LOWER LEVEL
BATTERIES
After checking the electrolyte level, reinstall the rear cover (see page
94).
42