Like jayeff has mentioned you may want to check the ratings of your new charger. But I am going to bet it's more an issue with the battery. Some devices will run off a charger even with the battery removed from the device. Since you are only able to use it while it is plugged into a charger I would assume the battery is the issue. Especially since you mentioned that an exclamation point appears in the battery icon. The exclamation point signals that there is an issue with the battery. Either the battery, the battery cable, or the batteries connection to the logic board. If any of these are faulty it will usually cause the exclamation point to appear in the battery icon. I would double check the battery's connection to the logic board and try reseating the battery connection on the logic board. If this does not help then replace the battery. This should fix the issue. Best of luck.