About 12 hours
The general green light will flash when charging, and if it does not flash, it means that it is fully charged. General electrical appliances can be continuously charged, do not consider a full, for convenience, you can always charge, use a few days to charge, this will not have any impact on the product.
Electric toothbrushes usually last 90 days on a full charge. If your electric toothbrush lasts a few days on a single charge, it is aging.