Unfortunately, some cheaper USB models do not seem to report BCHARGE in the apcaccess output listing, which means with a standard conf file, your system will be immediately shutdown. To correct this, set the BATTERYLEVEL directive in your apcupsd.conf file to -1.
Some of these cheaper USB UPSes also do not report the Voltage. This is annoying but does not cause the unit to malfunction.
If either you disconnect the UPS or it disconnects because of some electrical problem, it will most certainly reconnect with a different device number. Apcupsd will detect this and reconnect properly. However, apcupsd does not release the old device (USB port) lock file and create a new one. This is not too serious.
Currently (as of 3.10.6) the code to power off the UPS works only if you have a Linux kernel version 2.4.22 or greater, or you have applied the patches in the examples directory to your kernel.
If apcupsd does not connect to the USB port when you reboot, it is probably the appropriate kernel modules are not getting loaded correctly.
You can check this by bringing up your system, fiddling around until you get apcupsd to work with the UPS, then doing cat /proc/modules andnd save the output some place. Then reboot your computer and before you do anything else, do the cat /proc/modules again. Most likely you will find some of the usb modules are missing in the second listing.
There are two solutions:
You might want to read the man page on hotplug, and it might be necessary to cp /etc/hotplug/usb.rc /etc/init.d/hotplug to get it fully working.
/sbin/modprobe <missing-module-name>
in the /etc/rc.d/init.d/apcupsd script just after the start) case (at about line 17). This will force the modules to be loaded before apcupsd is invoked.