How do I check the status of the CMOS battery?

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

4 Answers

$ cat /proc/driver/rtc | grep batt batt_status : okay 

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) 

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.

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

• The Signs of a Bad CMOS Battery

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.