ive tryed to charge my prestigio multipad pmp5097CPRO but it wont?

hi i have a prestigio multipad pmp5097cpro ive tryed to charge it through a usb into my computer but i understand you cant so i tryed through the mains and still wont charge all i get is the startup screen and then it turns off and restarts if you plug it into the mains but if i plug it in my laptop using usb it turns on and goes onto the home page then after 15 seconds it turns off again .. tbh i think i need new batterys for it but dnt have a clue on what batterys they are.. can anybody help many thanks in advance