Plug battery in and lights don't go on
The battery is failing and is starting to degrade. If you can't get it to take a full charge, you might want to mark it for use in your flashlight only, but eventually, the battery won't take any charge and you'll have to replace it.
The good news is the the Ryobi battery tools have the lowest cost of rechargeable batteries in the marketplace. I believe you can purchase a 2 pack at Home Depot for under $40.00 which is very inexpensive for two (2) Ni-Cad batteries.
If you battery is from a new tool set, just simply contact Ryobi Customer Service and they'll address the problem with a replacement. If the batteries are ones you've been using for awhile, then go for the replacement.
NiCad batteries should be used until the tool slows down to the point where you can't use it. Then remove the battery from the tool and allow it to cool down for about 15-20 minutes before placing it in the charger. This will provide the maximum working life for your batteries.
When you use a battery powered tool, the battery gets warm/hot as it discharges, and then it gets heated up during the recharging process, so letting it cool down after using it, will prolong the useful life of that battery.
Hope you find this Very Helpful and best regards! Read More At : 3-piece 18V Drill / Circular Saw / Light Combo Tool Sets...