Can I charge Ryobi lithium battery with NiCad charger?
Thereof, can you charge a lithium ion battery with a NiCad charger?
NiCad and NiMH batteries are amongst the hardest batteries to charge. Whereas with lithium ion and lead acid batteries you can control overcharge by just setting a maximum charge voltage, the nickel based batteries don't have a "float charge" voltage. So the charging is based on forcing current through the battery.
Herein, can I charge a Ryobi lithium battery regular charger?
Yes, the lithium batteries will work just fine in any of the older (blue) 18 volt Ryobi products. You will have to buy a lithium battery charger though. Do not attempt to use the old NiCad charger
They are interchangeable. Any of the One+ batteries (NiCad Black and Yellow, Lithium, or Lithium+) will work in any of the Blue or green tools. Only thing you can't do is charge the newer lithium batteries with the old NiCad chargers.