Ryobi p111 charger -- light stays red even if battery left charging overnight.

Bad battery, I have had similar issues with rechargable batteries for tools. Replace them.

If only the red light is flashing then the battery is not charging at all. Ryobi identifies in the manual that batteries will not charge below 43 degress F. If your batteries and charger are in the garage in a cold climate, warm the batteries to room temp in the house and then try again. If the charge starts when the batteries are warm they will continue charging for the full cycle even in a cold area.

If you are sure your charger is working properly then your one battery may be shot.. i even had a new battery quit charging and had to replace it. they do not come cheap.

see if your charger is under warranty and have it replaced..yours is bad..

Use
AC / DC Power Adapter Replaces Ryobi One+ Batteryhttp://lcdpayless.com/ryobi_one_power_adapter.php

When it is brand new only. If charged overnight and still does not last take back to purchase place and have them test battery..then make them replace it if it is bad...:)

For others with the same problem (flashing red light won't go off)...make sure you FIRMLY PUSH the battery down onto the charger and engage the latches. Simply resting the battery on the charger will not work.

Just was on a website for Ryobi drills and it states that if the yellow and green light stay on for more than 15 minutes the battery is fried. Couldn't find the link but if you do a search for Ryobi Drill 18 volt you should find the same info. It was as product review from Australia I think.

I also have a problem with the charging of Ryobi batterys. They seem to charge AOK with the green light coming on but the charge does not last at all. Not sure if the problem is with the batteries on the charger.

Wait, how long have you waited for it to charge? It's supposed to stay red until over 80% charge, then switch to yellow. When it is fully charged, it goes to green. When you mean it stays red when plugged in, have you waited the 2 hours?