You'll want to refer to the owner's manual included with the scooter or the manufacturer's website to determine the appropriate capacity battery charger for the scooter model.
VidaCura offers chargers in the following capacities:
2 Amp, 3 Amp, 4 Amp, 5 Amp and 6 Amp.
You can always use a battery charger of a larger Amp rating, but never a smaller one. For example, if your scooter requires a 3.5 amp charger, you would purchase a 4 amp charger.
If your scooter came with a 12 AH battery, it may have come with a 1.5 Amp (1500 ma) battery charger. If you're upgrading your scooter battery pack to a larger one like a 20 AH battery, while this charger is sufficient to charge the 20 AH battery, you'll get better results if you also upgrade your battery charger to a 2 Amp unit.