Wow!
Not too many folks ask questions like this. As an old fan of soldering just about anything - I would make a few suggstions.
First - 10 gage wire is pretty heavy - and thus it's ability to conduct heat AWAY from the soldering point is pretty good.
Second - A 25W iron ISN"T all that great for soldering big stuff. Do you have access to a Weller gun? that has 125 to 150W? (perhaps you had a typo at 25W) If so that should clear up your problem.
Third - Some wire has a "coating" on it that makes it more difficult to "tin" it prior to soldering. You may need to spread and flatten it out and scrape it with a sharp blade in order to expose the bare copper - so that you can tin it.
Well, thats about all I can think of right now.
Let us know how it turns out!
Randyman
