The solution to your problem lies in one of the following three areas:
Your charger is faulty and is therefore not able to pass power to your laptops battery.
The charging connector on the laptop has come loose from the contacts. Therefore a bad connection.
Your battery is faulty.
If you are sure that your laptop charger is dead and you are in the market for a new one, try the following one:Replacement Acer Aspire 5750 AC Adapter 90Watt 19V 4.74A