Question Is CMOS Battery in laptop redundant when main laptop battery is present?

Mar 24, 2019
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Does the laptop’s main battery power the RTC and CMOS settings (regardless of the CMOS battery CR2032 being present on the motherboard) when the laptop is shut down, but Laptop battery has charge and is connected to the motherboard which is usually the case?

Does CMOS battery come into effect only when the main laptop battery is dead or removed and laptop is not plugged in to mains?

If so theoretically if my laptop battery is never going to drain to 0 then CMOS battery would be redundant? Is it so?

Background – My old laptop’s BIOS cell holder is broken and the cell does not firmly fit in. Laptop is given for repairs, so I am trying to understand if that CMOS battery would really be needed in future.
 
Mar 24, 2019
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its needed as the last power resort. unplugged and changing the laptop battery, with no CMOS battery you will need to reset all the settings at every power loss.
Thanks. So by power loss do you mean removal of the main battery? That's what my query is.
 

R_1

Splendid
Herald
without the CMOS battery power loss mean, no main power OR laptop battery.
if battery to laptop is removed and the plug comes lose, or dead battery and the plug comes lose.
the CMOS was the redundancy power for those settings, without it the unit will need constant power from one of the other sources at all times or you will need to reset the BIOS settings ( time and date- RAM speed, etc.) at every power loss.
 
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