Fuze battery life difference between Version 1 and 2 ?

I’ve had three 8gb Fuzes. One was a V1 and two ver V2’s. The V1 had siginifcantly longer life between charges versus the newer models. What changed in the hardware between these units? I know it isn’t the settings or the mp3’s because I’m playing pretty much the same stuff. I download a lot of podcasts and radio shows that are at a relatively low bitrate. Anybody done an A-B comparison between a V1 and V2 ?