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I have found myself in situtations where the internal battery has been used frequently. How do I check its status without diving into the mountain of directories?

NOTE I need to know about the CMOS battery. not the laptop's power supply, so this isn't a duplicate of those questions

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    If you mean the CMOS battery, please update your question and its title to say so – “internal” is a rather puzzling term, as laptop batteries are usually internal. – dessert Aug 14 '17 at 10:10
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    Just a link cuz this is probably what you need: manpages.ubuntu.com/manpages/xenial/man4/nvram.4freebsd.html But nooooooooo idea how since it differs per system .... Edit about close votes removed; If you have complaints post that on meta.askubuntu.com and otherwise: after it is closed it can be re-opened – Rinzwind Aug 14 '17 at 10:33
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$ cat /proc/driver/rtc | grep batt
batt_status     : okay
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    Relevant note: "CMOS" is a tiny bit of very low power static memory that lives on the same chip as the Real-Time Clock. It is fairly convenient to actually think of the RTC as being "part" of CMOS. -- OSDev Wiki – user37165 Nov 4 '19 at 5:52
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use app lm_sensors:

$ sensors-detect

next , run sensors and look for Vbat value:

$ sensors
it8718-isa-0290
Adapter: ISA adapter
in0:          +1.18 V  (min =  +0.00 V, max =  +4.08 V)
in1:          +1.89 V  (min =  +0.00 V, max =  +4.08 V)
in2:          +3.31 V  (min =  +0.00 V, max =  +4.08 V)
+5V:          +2.91 V  (min =  +0.00 V, max =  +4.08 V)
in4:          +0.69 V  (min =  +0.00 V, max =  +4.08 V)
in5:          +0.08 V  (min =  +0.00 V, max =  +4.08 V)
in6:          +0.42 V  (min =  +0.00 V, max =  +4.08 V)
in7:          +2.93 V  (min =  +0.00 V, max =  +4.08 V)
Vbat:         +2.94 V  
fan1:        1713 RPM  (min =    0 RPM)
fan2:        1558 RPM  (min =    0 RPM)
fan3:           0 RPM  (min =    0 RPM)
fan4:           0 RPM  (min =    0 RPM)
temp1:        +48.0°C  (low  = +127.0°C, high = +127.0°C)  sensor = thermistor
temp2:        +39.0°C  (low  = +127.0°C, high = +70.0°C)  sensor = thermal diode
temp3:         -2.0°C  (low  = +127.0°C, high = +127.0°C)  sensor = thermistor
intrusion0:  ALARM

radeon-pci-0100
Adapter: PCI adapter
temp1:        +55.0°C  

coretemp-isa-0000
Adapter: ISA adapter
Core 0:       +56.0°C  (high = +80.0°C, crit = +100.0°C)
Core 1:       +55.0°C  (high = +80.0°C, crit = +100.0°C)
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    And which of those figures is the CMOS battery? – PerlDuck Aug 23 '18 at 9:31
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    This screen: Vbat: +2.94 V but your system it may be Battery or another, all depends from modules detected in sensors-detect – zersh Aug 23 '18 at 9:41
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    I tried that, I get multiple temp sensors and fan status. Nothing on voltages. – Death_by_Ch0colate Sep 2 '18 at 0:48
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If you open up the laptop, you can use a multimeter to check the voltmeter reading of the CMOS battery. This is the only reliable way that I know of.

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The sensors command doesn't output the CMOS battery voltage for my laptop. This article gives other pointers:

To summarize the link:

A constant beeping sound is another sign that your CMOS battery is dying. The final sign that your CMOS battery is going dead is that you'll receive an error message. The three main types of error messages are: CMOS Checksum Error, CMOS Read Error and CMOS Battery Failure.

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