Usually when he CMOS battery is failing the computers time & date change & have to be reset manually. So if the time & date are remaining correct after an overnight shut down, the CMOS battery is probably OK.

Having to run CHKDSK Assist every time is very likely indicating your hard drive is failing & may die at any time, so it might be a good idea to get a new hard drive & clone your existing one to it & then install this new drive & use it as your main drive.