Good battery saver app for MyTouch 4G Slide? Or a decent replacement battery?

[Diso]

I just switched to T-Mobile and I've got a used MyTouch 4G Slide from ebay. I'm loving it so far except for the battery life. I was using JuiceDefender for a while but I had a problem with data not coming back when I'd unlock the phone. I know it wouldn't come back instantly but we're talking 5+ minutes here and still no data coverage. I'd have to reboot to get it back. This wasn't a consistent problem and I did see an improvement in battery life so I'm looking for a replacement app. There are a lot to choose from in the Play store, does anyone have any suggestions of one that works well?

Also, any suggestions for a higher capacity battery? I don't want to get an extended battery that requires a special back. I've got my phone in a case and I'd like to keep it that way. Several reviewers on Amazon mention the EVO 3D battery from CHICHITEC. Does that really work?

I've done just about everything I can think of to preserve battery life. My apps sync every six hours, GPS and Bluetooth are off, screen is on the lower end of the brightness scale and I don't have animated wallpaper. The only widget I have is the Sense clock with weather, which I use. I try my best to turn off mobile data when I have no coverage.

[anabolina]

I'm sorry JuiceDefender didn't work for you.I use it on my HD2 and had almost twice as much battery left after work.Yes, I also had some delays in 3g coming back on but it was always back after a few moments.

I've tried some ebay extended batteries that did nothing but make the phone look funky. Sometimes batteries get old too. I bought a new non-extended battery for the HD2 and it got much better battery life than the 2+ year old OEM one.

Are there any cases with a built in battery?