|"...i need to press f10 when booting up. Can't do it on restart..."|
The reason you can't use F10 when rebooting is that the reboot bypasses the BIOS settings---it already knows what the parameters of the machine are. You have to use F10 from a cold-boot.
"Anyway in the bios under the tools menu >battery configuration there is an applet...."
I think you're getting "BIOS battery" and "system battery" confused. There generally isn't any way to recharge a BIOS battery on almost all machines (the RTC battery is what the HP page refers to it as). The system battery is what keeps your notebook running when it's not connected to AC. If you're having date/time issues it's almost always a BIOS (RTC) battery that's at fault. You state that you've changed BIOS batteries before; looks like you need to again if you haven't recently.
"Channeling the spirit of jboy..."