battery was reported very low while booted and after long night of cha

i left my ipod to charge overnight and i noticed that the battery still showed that it was extremely low. booting into rockbox it was showing that it was at 0%, then fluctuated between 9% and up to 30%. now it died, and now it is showing “please wait. Very low battery”. i read somewhere it could be the battery chip or something. the battery was working fine before and it is not swollen, and is not a replacement battery. what could i check?

edit: i tried another battery, and i believe it reports properly. i will test this but it might work, and perhaps something in the battery busted. would this be a logical hypothesis?