'Reddish Black'/dirty wire on battery ????

[Graiskye]

Did a quick search but couldn't really find anything pertaining to this.
What I am dealing with is my first Lipo bought, that I have to solder the connector on.
Know Ive got soldering experience and generally have been pretty consistent, so 'No biggie!', or so I I thought.
I got the battery earlier today, and I got the male JST, the battery is a 'FlitePower EVO20 800MAH 2S1P 7.4v.', so I get ready to solder,I tin the end of the JST no problems, go too tin the ends of the battery, and nothing it will not take he solder. The wire has a dark reddish appearance, I'm wondering if this is corrosion of some sort, should I be worried for the safety/reliability of the battery ?
Iv only got about 2.5" of good lead left, I have hacked off about an inch trying to get a decent tin, but it just wont take the solder.
I don't have any flux, and have just been using my regular old 'electronics' solder, which has always done me well in the past, and works fine on the JST, which has nice silver wire.
Any ideas, should I just cut more wire off, looking for clean stuff or can I clean the wire somehow, maybe sanding it or ????
Thanks for any help.
-Grais.

[BritOnTour]

Yep, it sounds like copper oxidation to me. Maybe the pack was stored in a humid atmosphere. strange that it has gone so far down the wire under the plastic coating. However, if you can clean it off, it should work just fine. try some wire wool, or maybe some baking soda on a sponge. just spread the bare wires apart and rub the wire wool/sponge from the sheathing to the wire ends.

If the solder you have is flux cored (rosin flux inside the solder) then that should be able to remove the tarnish if it isnt too bad. Apply a liberal amount of solder to the iron and if there's a bubbling liquid, then the solder is cored. Apply the hot solder to the cable and add more solder to the joint as it starts to flow onto the wire.

If your solder isnt cored, then throw it away and get some from Radio Shack or similar. It's not worth the hassle to mess with uncored solder for delicate electrical work like this.

[Graiskye]

Hey thanks BoT. As a floow up, yes it was oxidized, and yes some lfux solder from RS, or better known as 'the Source' now,and it fixed me up.
Also bought a proper 60w variable temp iron.
Now I can solder everything save for some massive connectors for RC FullSize tanks or such. Lipos the size of a large suitcase....lol.
-Grais.

[istandalone]

^^you mean those 20s6p cells? that are for 360 class helis?