You should never leave your battery charger plugged into your scooter battery for longer than 8-12 hours. It can overcharge and damage the battery.
Scooters that are being used daily should be charged each night for a full 10 to 12 hrs.
Also, scooters that are used infrequently still need to have the battery charged regularly, once every 5-6 days for a full 8-12hrs. A scooter battery that isn't charged, will after a period of months, discharge and be unable to be recharged. It will need to be replaced and would not be covered under any warranty.