Honda GL1800 2004 Owner's Manual page 166

Battery Storage
Refer to Saf ety Precautions
If you plan to store your motorcycle, we recommend you remove the battery and
store it where it can be charged at least every 30 days to maintain its service life.
If you do not remove the battery, we recommend disconnecting the battery
cables (negative cable first).
You will get the best storage results from removing the battery and slow
(trickle) charging it every 30 days (see
Before you remove the battery, be sure to read all the information that follows,
as well as the information on the battery label.
on page 106 .
Battery Charging,
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.
Battery
page 161 ).
Servicing Your Honda
159