Even after leaving the batteries charging for over 24 hours the cell #2 is still red. Do I need a replacement? Ella at SwiftPaws March 10, 2020 15:50 Updated It sounds like you might have a bad cell. Please contact Support@SwitfPaws.com and describe your troubleshooting efforts and the results so we can best determine your needs. Thank you! Related articles After I plugged the battery in the charger, it smells and is not charging. What do I do?