I have a Ryobi multi volt charger and two Ryobi 18V Li-ion Batteries. Even though I have used both batteries down to where they don’t function anymore, the charger doesn’t charge them. The Red light flashes, and then after a very long time (hours) it flashes two short and on long flash. Why doesnât my charger is charging Ryobi batteries? What is the problem? What can do about it? I would really appreciate your useful information regarding this. Thanks.