Have a look at this post about why task killers aren't that useful.

Your problem could be that the task killer is continually killing an app (or several apps and processes) that your phone's system is launching when it can't find it. This can easily represent a huge drain on the battery.

I don't know how you use your phone and how much you're getting from your battery, but the biggest drain is usually the screen, so cutting screen time and brightness should make a big difference. By comparison, other processes, except for maybe Dialer, will be small. Menu > Settings > About phone > Battery > Battery use.

 

I believe that the general consensus of opinion is that the operation system will look after itself and any app. killer is not required and will have the opposite effect as your system has to keep on restarting things - get rid of it pronto and keep your screen's brightness, where possible down to <25%, preferably about 15% if indoors.
Also turn off wi-fi, GPS and bluetooth unless you need them.

 

There's your answer to your rapid battery drain, then. Don't you have a power supply from your car?

 

Using WiFi when you have WiFi access will possibly increase battery life as 3G/GPRS won't be used for data any more. Maybe try something like Llama to switch these things on and off automatically depending on your physical location. I have it turn on Bluetooth when I'm not at home or work only, and WiFi is on only when I'm at those places. I also have it reduce notifcation volumes when I'm at work (quiet office) and have them very loud when not at home or the office. Etc etc...

 

No idea. It might.

 

Well, I think it's easier than some of the extremely well rated alternatives like Tasker, though tasker is more capable.

And it's a free app, which is a bonus, and I find it works without drama once set up.