[EVO 4G Android Development] raphenucleus:
Like many people have reported on here, after flashing 1.2 stable I experienced a very noticeable decrease in battery life over previous builds (my GPS worked fine, though). I was getting about 10-15 hours on a single charge, whereas before I could easily get over 30 hours with the same usage. For reference, I'm running SavagedZen 2.2.1 CFS with voltage decreased by 75mV using viperMOD. I saw this thread about flashing a specific combination of Radio/PRI/NV/Wimax/GPS to fix the high Android System/Android OS usage in the battery stats and thought I might try it to see if it would increase my battery life.

The first time I tried it, I flashed the combination of:

Radio: 2.15.00.05.02

PRI: 1.77_003

NV: 1.90_003

WiMAX: 27243

GPS: HTC VISION GPS ".so" file

and it didn't work. I saw no improvement in battery life and Android System was still high as ever in the battery stats. I repeated this same fix a second time, as per the instructions, and it still didn't work.

The third time, I flashed the same combination, except this time I downgraded the NV to 1.77_003, as the instructions say if the first method doesn't work. Still nothing. So for me at least, it doesn't appear that changing the radios had much, if any, effect on my battery drain problem.

I finally decided to try flashing a different GPS driver to see if that would fix things. I read in the same thread that some people who were using the CyanogenMOD 7 Nightly 39 GPS Driver were getting really good battery life, so I decided to try that one. I wiped the cache and dalvik cache, flashed the CM7 n39 GPS driver, fixed apk uid mismatches, and rebooted. I then charged the battery to 100%, rebooted again, and used the phone a bit. After making a couple of phone calls, using the internet for a little while, messing around with maps and navigation, I noticed that the battery was draining a lot slower. I know that's certainly not anything definitive since the battery needs time to recalibrate and everything, but it's been over a day now on a single charge and I still have about 30% left. My battery would have died hours ago if I were on the same configuration as I was before I tried any of this.

One thing to note, though, is that my GPS was a little screwy after I first flashed the CM7 n39 GPS driver; it worked, but it did that thing where the icon would keep blinking in the status bar after I closed maps or navigation or whatever application was using GPS. I did the Sense GPS fix and that fixed the problem right away. My GPS is working flawlessly now. None of this did anything to lower Android System in my battery stats, but that doesn't really matter since it improved my batter life.

Since it appears that it was the HTC Vision GPS driver that was causing the excessive battery drain for me, I'm going to try flashing different combinations of Radio/PRI/NV/Wimax to see if I can get the same or better battery life out of using newer versions of them in combination with the CM7 n39 GPS driver. But in case I've struck the magic combination and people want to see if it works for them too, here's what I'm using right now:

ROM: Deck 1.2 stable

Kernel: SavagedZen 2.2.1 CFS

Hardware Revision: 003

Radio: 2.15.00.05.02

PRI: 1.77_003

NV: 1.77_003

WiMAX: 27243

GPS: CyanogenMOD 7 Nightly 39 GPS Driver

EDIT: Added link to download the CM7 n39 GPS driver (taken from this thread). Just FYI, it's recommended to wipe Dalvik and cache before flashing and fix apk uid mismatches (fix permissions) after.