Cmos battery issue? Maybe.

Hello,

I have a toshiba laptop (satellite pro s300) which I do not use much. Recently it started saying it has a "low rtc battery or cmos check sum... Press F1". It lets me update the time and date but when I save and exit it does not reboot.

So I found and replaced the rtc battery and it hasn't helped (I did get it to boot once with the new battery in but only one time). I have left it plugged in and turned on for about 8hrs in the hope of charging up the rtc battery.

Can anyone suggest what I can try next?

Thanks in advance.

Neil