are Li-Ion and Ni-Cad battery packs compatable?

So.... *sniffle* no one wants to answer my question? :'(

If you can stop a 300 ft pound impact wrench it isn't worth owning unless there is a torque setting and you have it on the weakest setting. Regarding the batteries, tools are usually one or the other meaning that if it comes with NiCad or Li Ion there is no switching to the other or why would they produce two batts for the same device. If you HAVE a choice Li ion batts are very light in weight by comparison to 18V NiCads are. I have two cordless drills I use/used. One is an 18 volt DeWalt with NiCad and the other is Rigid with Li Ion, they are both the same relative age ( maybe 6 months between the two) . My DeWalt is still going strong 8 years later, but the Rigid with compact Li Ion batts are BOTH dead and gone: no recharging will kick them over. I called customer service to see if I could find out whether it was the charger or the batts. They weren't any help so I got another charger and the batts came up as defective. At $100 each I am in no hurry to replace them because the DeWalt is still going strong. So I am convinced Li Ion is one I personally will avoid going forward.