Our Homelite Electric Lawn Mower is not charging. When initially plugged in,
The charger showed one green light and one red light. It is supposed to take 15 hours, but it has been more than a whole day and it's still not showing two green lights. Is the charger bad or do we need a new mower battery?

I'm going to guess it's the battery... how old is this?

Rechargeable batteries do go bad but we need to see if your charger is working. Remove the battery and put two test leads on the charger probes, be sure to use a tester designed for your voltage