The following disables the Logitech Headset buttons as input device (to avoid messing up mouse input). The mute button still works, but volume control is disabled as well.

http://www.g8rengineer.com/#/article/726

lsusb
#identify the ID of logitech headset i.e. 
#Bus 001 Device 007: ID 046d:0a49 Logitech, Inc. 

sudo tee /usr/share/X11/xorg.conf.d/50-LogitechInc.conf << EOF
Section "InputClass"
    Identifier "Logitech, Inc."
    MatchUSBID "046d:0a49"
    Option "Ignore" "on"
EndSection
EOF

This is debug tests to possible enable the buttons on the Logitech H820e headset.

xinput disable "Logitech Inc Logitech H820e"
xinput get-button-map "Logitech Inc Logitech H820e"
14 15 0 0 0 0 0 0 

xinput reattach "Logitech Inc Logitech H820e" "headset pointer"

xinput --create "master headset" sendCore=0

#!/bin/bash

xinput list | grep "main keyboard" -c > /dev/null

if [ $? -ne 0 ]; then
  echo "Splitting laptop leyboard and touchpad..."
  echo "Creating xinput main"
  xinput create-master "main"
  echo "Reattaching laptop touchpad and keyboard to main"
  xinput reattach "SynPS/2 Synaptics TouchPad" "main pointer"
  xinput reattach "AT Translated Set 2 keyboard" "main keyboard"
else
  echo "Merging laptop keyboard and touchpad..."
  echo "Reattaching laptop touchpad and keyboard to core"
  xinput reattach "SynPS/2 Synaptics TouchPad" "Virtual core pointer"
  xinput reattach "AT Translated Set 2 keyboard" "Virtual core keyboard"
  echo "Removing xinput main"
  xinput remove-master "main keyboard"
fi

Images of location of the rechargeable Li-ion battery for replacement.
Battery specs and numbers:
430mAh 3.7V 1.6Wh
533-000095
AHB582930
L/N 1307
3402076-0612

Dimensions: 28.5mm x 28.5mm x 6.5mm