Replacement Battery Not Charging - Tried two new batteries

Ok, so my iphone battery has been on the blink for some time, cutting out at 50-70% and not turning back on until plugged in. This is annoying as I am travelling around the world and having music and apps for those long journeys is very useful to me

I got a new battery from ifixit and followed the guide ok but after replacing it it would not turn on or charge even after overnight. So I switched back the old battery and it was working fine, but again cutting out randomly. Dead battery I thought. As I was on the road sending it back and getting another shipped was not an option, so I got to Bangkok and got another new iphone 3GS battery did the same replacement guide and I'm having the same problem, I find it hard to believe that both would be DOA. I have tried DFU mode which itunes recognises but as soon as it tries to restore to factory settings (I see the apple icon on the screen) I then get an unknown itunes error. Again the old battery it working after switching it out.

Does anyone have any ideas?