Update guys,
I ended up buying the "fattest" tip that I could find, and got the right solder. I just put 7 traxxas ends on batteries that I have had for awhile , but just have not had the time to work on them. The "tips" I got from you guys made all the difference in the world.I put it off because it was such a frustrating experience. This time all 7 went off without a hitch

I think I will keep my 936 for awhile