You get that notification majorly due to prolonged storage of the mac.
Best thing to do is to charge in off position for 5hours. power on and use up the battery totally. Repeat this cycle two to three times, the notification will clear. You might notice your battery sometimes remains on 97% even when fully charged, thats just by the way, it will still last more than 3 hours.
But in a situation your battery barely crosses the 2hr mark, it might need replacement.
Chi'