E1-572G discharges when playing game even when plugged in

I sent my laptop for warranty twice but still the problem continues. My laptop always discharges when playing games even when plugged in. Sometimes when i only browsing the web or doing microsoft word it tends to discharges. The problem starts when i disconnect my battery, plugged my ac adapter and played games. Then, the laptop suddenly shuts down without warning. When i inserted the battery and plugged in the adapter, it automatically discharges and produce a single beeping sound, indicating that my laptop isn't charged in my opinion. Then, the battery light(orange) and the left corner light(blue) blinks several times, i don't know what those blinks mean. I already sent my laptop twice for warranty and they said that it was the motherboard problem. They claimed that they had changed it. Until now, the problem remains. Please help.