In my constant battle to increase the batter life of my Evo phone, including killing processes, juggling brightness, and only enabling hardware features when needed (e.g. Bluetooth and WiFi), I finally decided to take my co-workers advice make the easiest and most-effective update: Buy a new battery!
Now, don’t hate me for taking the easy route! This battery costs less than $10, and has 2.5 times the capacity of the standard Evo battery (the stock batter has 1500mAh, the new one has 3500mAh). The only setback is that it makes the phone bigger and heavier, but I have big pockets and carry around a 20 lb laptop bag, so this wasn’t a big deal for me.
You can buy one of the battery that I have from Amazon: HTC Evo 4G 3500mAh Extended Battery + Cover
Another setback for me is that my cool skins I bought and affixed to the panel that came with my phone are no longer there, but it’s definitely worth it. I’ve had this battery on my phone for about a month now and it really helps. Before having this battery, I would need to keep it charged at work thanks to a USB cable. But now, I can keep it in my pocket without worrying that the phone will be dead at the end of the day.
When you do get this battery, don’t worry that it doesn’t double your battery life immediately, the phone’s firmware keeps track of the battery charge history and will slowly reset itself, so it took a few weeks for my phone to recognize the new battery capacity. My girlfriend has her phone rooted, and has the clockwork mod bootloader installed. She was able to manually reset the battery charge history using that utility and immediately get the longer battery life effects.