If you can't find a prepackaged solution, you can roll your own.
As part of Xfce, the Generic Monitor panel item should be available in your panel's "Add New Items" list. If not, it should be available as xfce4-genmon-plugin in your repo. From it's About dialog: "Cyclically spawns a script/program, captures its output and displays the resulting string in the panel".
Using the Generic Monitor, you can run a script that returns the info you need, like the one I pieced together:
#!/usr/bin/perl
# stats.pl - returns CPU and RAM usage
# CPU stuff
my $cpuusage = `top -bn 2 -d 0.2 | grep '^%Cpu' | tail -n 1 | gawk '{print \$2+\$4+\$6}'`;
chomp $cpuusage;
$cpuusage =~ s/^([0-9][0-9]*)(\.[0-9][0-9]*)$/$1/;
printf "CPU: %02d%% ","$cpuusage";
# RAM stuff
my $total = `grep -e "^MemTotal" -m 1 /proc/meminfo`;
$total =~ s/([^0-9]*)([0-9]*)(.*)$/$2/;
my $available = `grep -e "^MemAvailable" -m 1 /proc/meminfo`;
$available =~ s/([^0-9]*)([0-9]*)(.*)$/$2/;
my $memusage = 100 - ($available / $total * 100);
printf "RAM: %02d%%\n","$memusage";
The CPU stuff is based on What are the methods available to get the CPU usage in Linux Command line?, and the RAM stuff is based on How can I get processor/RAM/disk specs from the Linux command Line?
Generic Monitor displays the output of stats.pl in a panel as expected (for comparison, the graphic CPU and RAM info is my conky display):
My machine's a desktop, so I have no battery. From poking around a bit, though, upower seems to look promising for the battery info. For example, see 5 Ways To Check Laptop Battery Status And Level From Linux Terminal.
