tablet wont stay on or come on without being plugged up

[wwnrtucker]

my android 4.1.1 JB tablet stay on or won't turn on without being plugged into the accharger or a usb even though the battery is full & factory reset didn't help, i have to keep my finger on the power button when i unplug it or it goes dark, any idea thanks info; Rocketchips RK3066,Dual cortex,
A9 CPU 1.6 GHZ,1GB Ram, 8GB HDD