Honda GOLDWING GL1800/A 2015 Owner's Manual page 213

Battery
Battery Storage
Refer to Safety Precautions on
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
charging it every 30 days (see Battery Charging,
Before you remove the battery, be sure to read all the information that follows,
as well as the information on the battery label.
210
Servicing Your Honda
page 154.
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.
page 212).