18 volt ryobi battery charger...green & yellow lights come on wha

talked to Ryobi and they are vague. It can either mean that the battery is bad, or the charger is bad and another one that maybe the contacts of the battery are dirty or not seating fully in charger. What I would look for in this instance first unplug the charger and look into charging slot to make sure the terminals of the charger are not bent and they come out into the cavity where battery would go. If not gently pull terminal into opening and retry. Sorry I couldn't be of more assistance

The same thing happend to my charger, i bought na new battrey, and now it charges normal again