Alphatime like they are not the same. You really can't fit i5800 battery into galaxy ace. Why would you claim such a thing?
Now for some useful information. The phone can be optimized to last long in standby mode, simply by turning off the data connection when not using it, and switching to 2G. You can let jucedefender do that for you, or APN access point to manualy turn connection on and off.
But what good is a smart phone in a standby mode? The moment you start using it for something like say playing games, you got 2 hours gaming on a full charge. Now that’s pathetic.
Here are some things you can do to keep CPU less busy.
Use bsplayer lite to watch movies. It uses hardware acceleration to decode videos. It will keep CPU consuming less than 150mW. Unlike other players that use software decoding and constantly hit cpu usage as high as 400mW. So you can get 5+ hours (depending on brightness settings) watching movies using bsplayer.
Generally browsers will remain under 150mW if you let them sit still, but the moment you start scrolling (CPU) or opening links (radio) the power consumption will peak. Now Opera mini seems to take least CPU power. Obviously turning on wifi and 3G will drain much faster. The best battery time can be achieved using the 2G network data connection together with opera mini. Opera mobile seems to have hardware acceleration but I yet have to test the power consumption.
Test the applications you frequently use. You can use the power tutor program to monitor power consumption and test your application.
I've found that some programs, even the simple book readers will just lock the CPU at 800MHz even if you let them stand still, doing nothing with constant 400mW drain. Uninstall such applications or use them for short periods.
Well games have a high CPU demand and subsequently power consumption, and there is nothing to do about that.
Basically you can get:
2-3 days in standby or,
2 hours of playing games, and using unoptimized applications or,
5+ hours using applications with good coding and or hardware acceleration.
Underclocking the CPU using setCPU has no effect, becouse optimized applications allready scale the cpu to 250mhz or 128mhz. And demanding applications will stutter when underclocked and won't consume much less power.