The charger may get warm during use, this is normal for some loads. If your loads don't heat up during use, that doesn't mean it's not working.
The chargers have built-in overload protection. But NO we recommend charging more than 10 hours at a time, if your battery model is Acid lead. If your battery is Lithium, NO we recommend charging more than 15 hours.
Use the original Electric Patine charger. When not using the Electric Scooter, store it with a good charge.