[ubuntu] System restarts when power adaptor is out

This is my first post so hopefully I follow the correct procedures. These threads have been a massive assistance to me but I have not been able to find a solution to the following. The closest problem I found was this:

http://ubuntuforums.org/showthread.php?t=2307018

In my case:

OS: ubuntu 15.10
System: Dell Inspiron 17R SE 7720
[more details below]

When the power adaptor is not plugged in, after a certain period (for example when the power level goes below 66%) when I trigger a certain event (for example opening a 'compose new message' in Thunderbird) the screen goes black and I receive the following message which stays on screen for only a moment:

fsck from util-linux 2.26.2

/dev/sda1: clean, 764792/60538880 files, 179373428/242129664 blocks


[ ok ] Started Light Display Manager.

[ ok ] Started ACPI event daemon.

The system then immediately restarts automatically and the log in screen appears even though my system does not require a log in when it boots up.

Any advice gratefully received.

My system details:

nic-inspiron-7720
description: Computer
width: 64 bits
capabilities: smbios-2.7 vsyscall32
*-core
description: Motherboard
physical id: 0
*-memory
description: System memory
physical id: 0
size: 7840MiB
*-cpu
product: Intel(R) Core(TM) i7-3630QM CPU @ 2.40GHz
vendor: Intel Corp.
physical id: 1
bus info: cpu@0
size: 3204MHz
capacity: 3400MHz
width: 64 bits
capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp x86-64 constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm ida arat epb pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase smep erms xsaveopt cpufreq
*-pci
description: Host bridge
product: 3rd Gen Core processor DRAM Controller
vendor: Intel Corporation
physical id: 100
bus info: pci@0000:00:00.0
version: 09
width: 32 bits
clock: 33MHz
configuration: driver=ivb_uncore
resources: irq:0
*-pci:0
description: PCI bridge
product: Xeon E3-1200 v2/3rd Gen Core processor PCI Express Root Port
vendor: Intel Corporation
physical id: 1
bus info: pci@0000:00:01.0
version: 09
width: 32 bits
clock: 33MHz
capabilities: pci pm msi pciexpress normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:24 ioport:3000(size=4096) memory:f0000000-f0ffffff ioport:c0000000(size=301989888)
*-display
description: VGA compatible controller
product: GK107M [GeForce GT 650M]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:01:00.0
version: a1
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress vga_controller bus_master cap_list
configuration: driver=nouveau latency=0
resources: irq:28 memory:f0000000-f0ffffff memory:c0000000-cfffffff memory:d0000000-d1ffffff ioport:3000(size=128)
*-display
description: VGA compatible controller
product: 3rd Gen Core processor Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 09
width: 64 bits
clock: 33MHz
capabilities: msi pm vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:29 memory:f1000000-f13fffff memory:e0000000-efffffff ioport:4000(size=64)
*-usb:0
description: USB controller
product: 7 Series/C210 Series Chipset Family USB xHCI Host Controller
vendor: Intel Corporation
physical id: 14
bus info: pci@0000:00:14.0
version: 04
width: 64 bits
clock: 33MHz
capabilities: pm msi xhci bus_master cap_list
configuration: driver=xhci_hcd latency=0
resources: irq:25 memory:f1600000-f160ffff
*-usbhost:0
product: xHCI Host Controller
vendor: Linux 4.2.0-34-generic xhci-hcd
physical id: 0
bus info: usb@2
logical name: usb2
version: 4.02
capabilities: usb-3.00
configuration: driver=hub slots=4 speed=5000Mbit/s
*-usbhost:1
product: xHCI Host Controller
vendor: Linux 4.2.0-34-generic xhci-hcd
physical id: 1
bus info: usb@1
logical name: usb1
version: 4.02
capabilities: usb-2.00
configuration: driver=hub slots=4 speed=480Mbit/s
*-usb
description: Generic USB device
product: 802.11 n WLAN
vendor: Ralink
physical id: 4
bus info: usb@1:4
version: 1.01
serial: 1.0
capabilities: usb-2.00
configuration: driver=rt2800usb maxpower=450mA speed=480Mbit/s
*-communication
description: Communication controller
product: 7 Series/C210 Series Chipset Family MEI Controller #1
vendor: Intel Corporation
physical id: 16
bus info: pci@0000:00:16.0
version: 04
width: 64 bits
clock: 33MHz
capabilities: pm msi bus_master cap_list
configuration: driver=mei_me latency=0
resources: irq:30 memory:f1615000-f161500f
*-usb:1
description: USB controller
product: 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2
vendor: Intel Corporation
physical id: 1a
bus info: pci@0000:00:1a.0
version: 04
width: 32 bits
clock: 33MHz
capabilities: pm debug ehci bus_master cap_list
configuration: driver=ehci-pci latency=0
resources: irq:16 memory:f161a000-f161a3ff
*-usbhost
product: EHCI Host Controller
vendor: Linux 4.2.0-34-generic ehci_hcd
physical id: 1
bus info: usb@3
logical name: usb3
version: 4.02
capabilities: usb-2.00
configuration: driver=hub slots=2 speed=480Mbit/s
*-usb
description: USB hub
product: Integrated Rate Matching Hub
vendor: Intel Corp.
physical id: 1
bus info: usb@3:1
version: 0.00
capabilities: usb-2.00
configuration: driver=hub slots=6 speed=480Mbit/s
*-usb:0
description: Generic USB device
product: USB2.0-CRW
vendor: Generic
physical id: 3
bus info: usb@3:1.3
version: 39.60
serial: 20100201396000000
capabilities: usb-2.00
configuration: driver=rtsx_usb maxpower=500mA speed=480Mbit/s
*-usb:1
description: Video
product: Laptop_Integrated_Webcam_HD
vendor: CKFB187F301030092840
physical id: 5
bus info: usb@3:1.5
version: 26.19
serial: 0x0001
capabilities: usb-2.00
configuration: driver=uvcvideo maxpower=500mA speed=480Mbit/s
*-multimedia
description: Audio device
product: 7 Series/C210 Series Chipset Family High Definition Audio Controller
vendor: Intel Corporation
physical id: 1b
bus info: pci@0000:00:1b.0
version: 04
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list
configuration: driver=snd_hda_intel latency=0
resources: irq:32 memory:f1610000-f1613fff
*-pci:1
description: PCI bridge
product: 7 Series/C210 Series Chipset Family PCI Express Root Port 1
vendor: Intel Corporation
physical id: 1c
bus info: pci@0000:00:1c.0
version: c4
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:16 memory:f1500000-f15fffff
*-network
description: Wireless interface
product: Centrino Wireless-N 2230
vendor: Intel Corporation
physical id: 0
bus info: pci@0000:02:00.0
logical name: wlp2s0
version: c4
serial: 84:a6:c8:ca:52:83
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress bus_master cap_list etheet physical wireless
configuration: broadcast=yes driver=iwlwifi driverversion=4.2.0-34-generic firmware=18.168.6.1 latency=0 link=no multicast=yes wireless=IEEE 802.11bgn
resources: irq:31 memory:f1500000-f1501fff
*-pci:2
description: PCI bridge
product: 7 Series/C210 Series Chipset Family PCI Express Root Port 5
vendor: Intel Corporation
physical id: 1c.4
bus info: pci@0000:00:1c.4
version: c4
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:16 ioport:2000(size=4096) ioport:f1400000(size=1048576)
*-network
description: Etheet interface
product: RTL8101/2/6E PCI Express Fast/Gigabit Etheet controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:03:00.0
logical name: enp3s0
version: 05
serial: 5c:f9:dd:51:18:60
size: 10Mbit/s
capacity: 100Mbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list etheet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl_nic/rtl8105e-1.fw latency=0 link=no multicast=yes port=MII speed=10Mbit/s
resources: irq:27 ioport:2000(size=256) memory:f1404000-f1404fff memory:f1400000-f1403fff
*-usb:2
description: USB controller
product: 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1
vendor: Intel Corporation
physical id: 1d
bus info: pci@0000:00:1d.0
version: 04
width: 32 bits
clock: 33MHz
capabilities: pm debug ehci bus_master cap_list
configuration: driver=ehci-pci latency=0
resources: irq:23 memory:f1619000-f16193ff
*-usbhost
product: EHCI Host Controller
vendor: Linux 4.2.0-34-generic ehci_hcd
physical id: 1
bus info: usb@4
logical name: usb4
version: 4.02
capabilities: usb-2.00
configuration: driver=hub slots=2 speed=480Mbit/s
*-usb
description: USB hub
product: Integrated Rate Matching Hub
vendor: Intel Corp.
physical id: 1
bus info: usb@4:1
version: 0.00
capabilities: usb-2.00
configuration: driver=hub slots=8 speed=480Mbit/s
*-usb
description: Bluetooth wireless interface
vendor: Intel Corp.
physical id: 5
bus info: usb@4:1.5
version: 78.69
capabilities: bluetooth usb-2.00
configuration: driver=btusb speed=12Mbit/s
*-isa
description: ISA bridge
product: HM77 Express Chipset LPC Controller
vendor: Intel Corporation
physical id: 1f
bus info: pci@0000:00:1f.0
version: 04
width: 32 bits
clock: 33MHz
capabilities: isa bus_master cap_list
configuration: driver=lpc_ich latency=0
resources: irq:0
*-storage
description: SATA controller
product: 7 Series Chipset Family 6-port SATA Controller [AHCI mode]
vendor: Intel Corporation
physical id: 1f.2
bus info: pci@0000:00:1f.2
version: 04
width: 32 bits
clock: 66MHz
capabilities: storage msi pm ahci_1.0 bus_master cap_list
configuration: driver=ahci latency=0
resources: irq:26 ioport:4088(size=8) ioport:409c(size=4) ioport:4080(size=8) ioport:4098(size=4) ioport:4060(size=32) memory:f1618000-f16187ff
*-serial UNCLAIMED
description: SMBus
product: 7 Series/C210 Series Chipset Family SMBus Controller
vendor: Intel Corporation
physical id: 1f.3
bus info: pci@0000:00:1f.3
version: 04
width: 64 bits
clock: 33MHz
configuration: latency=0
resources: memory:f1614000-f16140ff ioport:efa0(size=32)
*-scsi:0
physical id: 2
logical name: scsi0
capabilities: emulated
*-disk
description: ATA Disk
product: Samsung SSD 850
physical id: 0.0.0
bus info: scsi@0:0.0.0
logical name: /dev/sda
version: 1B6Q
serial: S21CNWAG207009Z
size: 931GiB (1TB)
capabilities: partitioned partitioned:dos
configuration: ansiversion=5 logicalsectorsize=512 sectorsize=512 signature=0008e976
*-volume:0
description: EXT4 volume
vendor: Linux
physical id: 1
bus info: scsi@0:0.0.0,1
logical name: /dev/sda1
logical name: /
version: 1.0
serial: 6ba8c4ea-7d82-49a7-82e9-a576cc629499
size: 923GiB
capacity: 923GiB
capabilities: primary bootable joualed extended_attributes large_files huge_files dir_nlink extents ext4 ext2 initialized
configuration: created=2015-11-22 12:23:19 filesystem=ext4 lastmountpoint=/ modified=2016-03-18 12:18:25 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,data=ordered mounted=2016-03-17 14:58:57 state=mounted
*-volume:1
description: Extended partition
physical id: 2
bus info: scsi@0:0.0.0,2
logical name: /dev/sda2
size: 8048MiB
capacity: 8048MiB
capabilities: primary extended partitioned partitioned:extended
*-logicalvolume
description: Linux swap / Solaris partition
physical id: 5
logical name: /dev/sda5
capacity: 8048MiB
capabilities: nofs
*-scsi:1
physical id: 3
logical name: scsi1
capabilities: emulated
*-disk
description: ATA Disk
product: ST2000LM003 HN-M
vendor: Seagate
physical id: 0.0.0
bus info: scsi@1:0.0.0
logical name: /dev/sdb
version: 0002
serial: S34FJ90G307547
size: 1863GiB (2TB)
capabilities: partitioned partitioned:dos
configuration: ansiversion=5 logicalsectorsize=512 sectorsize=4096 signature=ec46fcd9
*-volume
description: EXT4 volume
vendor: Linux
physical id: 1
bus info: scsi@1:0.0.0,1
logical name: /dev/sdb1
version: 1.0
serial: adc8b3b7-7674-4e53-8534-bf558eff6837
size: 1863GiB
capacity: 1863GiB
capabilities: primary joualed extended_attributes large_files huge_files dir_nlink extents ext4 ext2 initialized
configuration: created=2015-12-08 11:39:28 filesystem=ext4 label=2TBINTERNAL lastmountpoint=/media/nic/2TBINTERNAL modified=2016-03-17 16:36:06 mounted=2016-03-17 15:02:29 state=clean
*-scsi:2
physical id: 4
logical name: scsi3
capabilities: emulated
*-cdrom
description: DVD-RAM writer
product: DVD+-RW DS-8A8SH
vendor: PLDS
physical id: 0.0.0
bus info: scsi@3:0.0.0
logical name: /dev/cdrom
logical name: /dev/cdrw
logical name: /dev/dvd
logical name: /dev/dvdrw
logical name: /dev/sr0
version: KD13
capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram
configuration: ansiversion=5 status=nodisc
*-network
description: Wireless interface
physical id: 1
bus info: usb@1:4
logical name: wlx00c0ca58ddcd
serial: 00:c0:ca:58:dd:cd
capabilities: etheet physical wireless
configuration: broadcast=yes driver=rt2800usb driverversion=4.2.0-34-generic firmware=0.29 ip=192.168.1.201 link=yes multicast=yes wireless=IEEE 802.11bgn

Disk info:

sudo fdisk -l
Disk /dev/ram0: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram1: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram2: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram3: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram4: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram5: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram6: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram7: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram8: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram9: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram10: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram11: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram12: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram13: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram14: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/ram15: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x0008e976

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 1937039359 1937037312 923.7G 83 Linux
/dev/sda2 1937041406 1953523711 16482306 7.9G 5 Extended
/dev/sda5 1937041408 1953523711 16482304 7.9G 82 Linux swap / Solaris

Disk /dev/sdb: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xec46fcd9

Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 3907029167 3907027120 1.8T 83 Linux