Yes, charging will automatically cut off when the battery is fully charged. I can’t imagine it being done otherwise as it will result in a fire hazard. We haven’t settled on the charging rate just yet and it’s actually related to the second part of your question. To elaborate, you can use a single USB charger to charge multiple motors at the same time. How many you can charge depends on the rating of the charger (so-called chargers are a misnomer, they are really just 5V power adapters) as well as the charge rate of the motor. So if we set the charge rate at, say, 500mA, a typical 1A charger will only be able to handle two motors. If, however, we set the charge rate at 50mA, then a single charger will be able to keep 20 motors running. The downside to that is, it will take something like 200 hours (!!!) to fully charge the battery if someone is using it as a battery motor that is not constantly plugged in. But yes, in short it is possible to daisy chain many motors together and run only a single cable to the small USB charger.
Now, here’s a pic for those who like mechanical stuff. The motor and gears are currently being tested.
