Some folks use a Deltran Battery Tender pigtail attached to their battery to keep it charged up while not in use. They make a 12V cigarette lighter socket to plug into that pigtail. When you don't need it, just unplug it and keep it in the saddlebag. They use SAE 2-Pin Flat connectors.
This cable from Deltran hooks up to the battery:
The cigarette lighter adapter (3", 12", or 18" cable) from Powerlet Products just plugs in to the Deltran pigtail cable:
