My 2015 v60 gives battery low warning now. Even when I drive for 30min that it still give me the warning. While if I use the charger to charge the battery for 4-5hours, it will not give such warning for 2-3 days then it comes again.

I am thinking to buy a new battery and replace it. While, how i can be sure if it the battery is old or other problem? Do i need to reset the BMS after I charged the battery?

other than the warning message, everything seems to be fine.