Batteries have "C" rating which is how many times you can charge or discharge them in an hour. This magic number is closely linked to battery chemistry. A "6C"

Batteries have "C" rating which is how many times you can charge or discharge them in an hour. This magic number is closely linked to battery chemistry. A "6C" battery can be charged in 10 minutes as long as you have the power, while a 10C battery can charge in 6 minutes. You're right that sometimes charging speed is limited by the available power. Don't expect to fast charge a 130kWh Tesla at a 45kW charger or charge a 100Wh laptop on a 18W cellphone charger. In the case of these scooter batteries, you are mostly limited by the batteries C rating. Even if you watercooled them to stay at a happy temperature, you can only push the chemistry so much. Maybe if they switched to a different chemistry like Lithium Titanate they could chaemrge quicker. For now it is easier to use LiFePo batteries and just swap them out.