Install fdpowermon in the same way with:
sudo apt-get install fdpowermon
Next up it's slightly different since the sessions are different in LXLE. There are 5 sessions: G2-Paradigm, Netbook-Paradigm, OSX-Paradigm, Unity-Paradigm and XP-Paradigm so replace as appropriate.
gksu gedit /etc/xdg/lxsession/XP-Paradigm/autostart
Then append @fdpowermon as in the original how-to like so:
Save the file and exit, then logout and login and you'll now have a battery monitor applet, and we're done!