Interesting... Assuming due to the sleep bug in v19, my Radius battery was completely dead from non-use (while I had the P3 adapter stuck to my tank). I go to charge it, and nothing - it's dead dead. My current meter says it's drawing 90mA. After a little while, the screen lit up when I pressed fire, and the battery has a ? in the display (maybe due to no atty attached). Hummm... battery killed? It's not charging - well, 90mA trickle anyway. I'll leave it like that for a while and see what happens. If nothing, I'll take it out and put it in my Xtar.
Hopefully it's not undervolted - that's a dangerous situation, as it could lead to thermal runaway (aka, venting). With this new information, unless you use your Radius every day, I strongly recommend updating to v20 ASAP.