The CMOS battery also known as coin cell battery, is not there to provide power to the laptop when it is in operation, it is there to maintain a small amount of power to the CMOS when the laptop is powered off and unplugged. Without the CMOS battery, you would need to reset the clock every time you turned on the laptop, if the CMOS battery is corrupted, then the time setting will be always changing, if the
CMOS battery is damaged or discharged when in the adapter plug, the laptop immediately turn on itself.

There are three types of CMOS based on the interface used to connect with a laptop motherboard.
1- Socket/button Type (Hand removable).
2- Connector Type (unpluggable removable).
3- Solder Type (De-solder the pin to remove battery)
Since the battery has one positive (+) side and one negative (-) side, you need to be sure that you are connecting the battery correctly

Most coin cells in use today are non-rechargeable and are found in medical implants, watches, hearing aids, car keys and memory backup.
Testing the CMOS in a good condition or not. You measure it; if the CMOS voltage is 3V then CMOS is ok. If the voltage drops between 1v-0v then CMOS is not worth wearing.

CMOS battery is damaged or discharged when in the adapter plug, the laptop immediately turn on itself.

There are three types of CMOS based on the interface used to connect with a laptop motherboard.
1- Socket/button Type (Hand removable).
2- Connector Type (unpluggable removable).
3- Solder Type (De-solder the pin to remove battery)
Since the battery has one positive (+) side and one negative (-) side, you need to be sure that you are connecting the battery correctly

Most coin cells in use today are non-rechargeable and are found in medical implants, watches, hearing aids, car keys and memory backup.
Testing the CMOS in a good condition or not. You measure it; if the CMOS voltage is 3V then CMOS is ok. If the voltage drops between 1v-0v then CMOS is not worth wearing.
