Battery Problem (Charging but returns back to zero percent then back to normal)

I'm kinda frustrated about my macbook pro, I seriously want this to get fixed. My MBP is 2 1/2 years Last week My mbp shut downed by itself then I figured out that the problem was the battery so I replaced it then bought a new one. I bought a replacement battery not in the apple store but I bought it online(somewhere cheap).

so now the big problem was after installing the new battery my mbp is charging but it returns back to zero percent then back to normal, so I can't pull out the charger from my computer because it will shut down.

please help me.

thanks!

My macbook pro specs:

Mid 2010

Macbook pro 13 in

Model Information:

Serial Number: W0********7Z2

Manufacturer: DP

Device Name: bq20z451

Pack Lot Code: 0

PCB Lot Code: 0

Firmware Version: 3

Hardware Revision: 2

Cell Revision: 100

Charge Information:

Charge Remaining (mAh): 4184

Fully Charged: No

Charging: Yes

Full Charge Capacity (mAh): 5400

Health Information:

Cycle Count: 2

Condition: Replace Now

Battery Installed: Yes

Amperage (mA): 2175

Voltage (mV): 12293

System Power Settings:

AC Power:

System Sleep Timer (Minutes): 10

Disk Sleep Timer (Minutes): 10

Display Sleep Timer (Minutes): 10

Wake on AC Change: No

Wake on Clamshell Open: Yes

Wake on LAN: Yes

Current Power Source: Yes

Display Sleep Uses Dim: Yes

PrioritizeNetworkReachabilityOverSleep: 0

Battery Power:

System Sleep Timer (Minutes): 63

Disk Sleep Timer (Minutes): 10

Display Sleep Timer (Minutes): 62

Wake on AC Change: No

Wake on Clamshell Open: Yes

Display Sleep Uses Dim: Yes

Reduce Brightness: Yes

Hardware Configuration:

UPS Installed: No

AC Charger Information:

Connected: Yes

ID: 0x0100

Wattage (W): 60

Revision: 0x0000

Family: 0x0085

Serial Number: 0x00a140cc

Charging: Yes

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