I did not turn N800 off but leave it on by closing all applications and locking keyboard and screen. after I installed many applications, N800 turned itself off sooner, i feel it can last one day only when it is fully charged. I suspect PIM suit and fmradio.
my questions are:
1. if a hard-reboot is the easiest way to solve the problem?
2. if htop is the best to investigate the problem?

thanks.

does command top work?
I typed:
top
top -b -n 1
top -n 1
there is no output produced. and ctrl-c cannot kill it. i am patient to wait for a while. what is the problem?
thanks.

i can't help you with top, but i can recommend load-applet, a toolbar app with simple GUI that lists all running processes and how much memory and CPU they're using, and it lets you kill whichever one looks like it's draining your battery. i like load-applet, because it helps me figure out if an app just crashed on me or if the tablet's working and i need to be patient.

(couldn't help but notice you're almost a Senior Member. just remember, with great power comes great responsibility... )

I install load-applet, it is very nice.
before the installation, i hard-reboot the device, the battery consumption is not that big. I think it is necessary to do hard-reboot from time to time, especially after install/uninstall some applications.
new question: does it consume power when the applets like load-applet run in the background ?

another thing is i tried to install htop in x-term using apt-get command with root privilege. but it reports there is no package.
my n800 is not flashed into RD mode. is it the reason?
thanks

i suppose there's some law of physics that says it must, but i don't have any complaints about battery life with my tablet, and i always have load-applet running.

i don't know anything about R&D mode. i've never understood what it's for. but i think you should be able to install htop without R&D. it's not a particularly specialized development tool or anything. try different repositories. add chinook and extras, free and non-free repositories. htop should be in there somewhere. sorry i can't be of more help with that issue.