[cappy]

I have had the Diamond for a week now, and the Touch before that. Rather than measure battery life in hours or days, I measure my expected battery life by how each function on the phone drains the battery. For both the Diamond and the Touch, Bluetooth has been the greatest drain for me. With Bluetooth on (no calls, data, Wifi), I can expect an 8%-10% loss in battery per hour. In 8 hours, my battery is at 20%-30%. When Bluetooth is off (again, no calls, data, Wifi), I see a drain of 1%-2% per hour. In 24 hours, remaining battery will be 55%-60%. So I keep Bluetooth off unless I need it.

Phone calls drain about 20% per hour for me. 4.5 hours of phone calls means a 90% drain, plus the 1%-2% per hour mentioned above should leave a remaining battery at 1%-6%. That is about what HTC estimates. If I have Bluetooth on the whole time (whether I am actually using the Headset), add 10% to the 20% for the phone calls or 30% per hour of talk time. So the battery will only last a little over 3 hours.

I can expect a drain similar to the phone call drain when I use the Internet, about 20% per hour. Though I have not used Wifi yet, my guess is that it would be similar to the Bluetooth battery drain.

I have several programs installed, but only run them as needed and they do not seem to drain the battery appreciably, unless they are performing a task constantly. For example, WMP or Sprint TV each will provide a constant drain when playing because it is a constant load on the processor. But having the Calculator program open, or a settings dialog, etc. does not provide a constant drain so I do not worry about closing these types of programs.

This is the stock ROM with a few tweaks using Advanced Config and Diamond tweaks (just what they recommend in the defaults). I keep the light sensor active and usually turn the data connection off when it is not needed. I use the Second Today screen (you can do a Google search) and nueChem's Battery tools. They are always running. The GPS location setting is always On.

There is one big caveat. The estimates above are using the Airave, which provides a strong signal and keeps the radio from working too hard. Prior to the Airave, with my Touch, I did find much poorer battery life because I only got 1-3 bars. So the Airave is a good be1nchmark and the estimates will vary, depending upon signal strength.

Bottom line. In 8 hours with Bluetooth off and 2 hours of phone calls and/or data, I should have a battery level of 100%-(20%x2)-(2%x16) = 44% remaining. Say between 40-50% battery remaining at the end of 8 hours. At the end of 24 hours, same 2 hours in phone calls/data, the remaining battery should be 50%-(1%-2%x16) = 18%-32% remaining. With Bluetooth on, you can do the math. Battery life will be much less.

I love the phone and am quite satisfied with the battery life. HTC says about 4.5 hours of talk time and I find this to be accurate. I consider talk time and data time roughly equivalent. If you use 4.5 hours of talk time and/or data time, the battery will last 4.5 hours. But under normal use for me (about 2 hours of phone/data), using only Bluetooth as needed, I can expect at least 30 hours. About the same as the Touch.

My experience. Hope it helps.