How to ensure a long life for your battery
If you have not ridden your Vespa for weeks or months, chances are that the battery does not have enough power to run the starter, or needs to be replaced.
The lead-acid batteries used in Vespa scooters may no longer hold a full charge if discharged too fast.
Once a Vespa battery drops below the level required to start the motor (usually around 12.4 volts), that battery is starting to fail and will soon need replacement because it will no longer hold a full charge.
Keep in mind that your Vespa battery loses 0.5% to 1% of its output each day. The rate is very sensitive to temperature too. Summer temperatures and low winter temperatures are very hard on batteries. Unless you ride almost every day, you should get a battery tender to keep your battery charged.
The best thing you can do to ensure a long life for your battery (up to three years) is to ride your Vespa often and for longer distances, or purchase a battery tender.