Thanks for your help.
1. "a while" means "sometimes a half hour, sometimes five minutes". I am not sure.
2. The 1Amper charger still displays the same behavior.
3. I've found the problem. In the Thing's Properties, There is a attributes which called "Data Change Info". Set the "Data Change type" to "Always". Because my data always the same as before, and the default of the "Data Change type" is "Values 0", so the same data change event can't be fired.