I too used a fast charger for months with no issues but then it started getting hot. i stopped using it and havnt used it since, and now 2 of my controllers are dead. i have now replaced both batteries with new ones... Twice! first with 2000mAh batteries , to no avail... and then with the factory 1000 mAh batteries. so far they are both getting hot and not holding a charge for more a few mins.
not sure at this poiint maybe i fried the charging port?