Help cannot get past the samsung start up


My brother in law has the Samsung galaxy ace GT-S5830

it has not been working for a couple of weeks now - i have tried and failed many times to access the reboot menu but it will not allow me to do this, I have downloaded odin and updated the firmware which passed but it still will not take me by the startup screen.

the phone has a cheap battery and i suspect this may be part of the problem so he is going out to buy another authentic samsung one tomorrow.

but even when plugged in to the usb it keeps rebooting all the time - getting to the start up page and then reboots. but it will not start without the usb (hence my battery theory)

any further advice would be great as to what our next steps should be