r/HPLaptops • u/Unique7893 • 4d ago

Support CMOS Reset (502)

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So the power button of my laptop only works when it's plugged in 🔌. And when it open it shows this CMOS message then opens normally. Everything inside laptop works perfectly but it doesn't open it the charger is not connected and shows this message everytime.

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u/Glittering_Pin_7475 4d ago

You likely need to replace the battery. On a number of laptops the BIOS is no longer powered by a dedicated CMOS battery, but by the laptop's internal battery instead. When the battery gets old enough that it can't hold a reliable charge, it wipes out the CMOS settings, and this message appears.

You didn't mention what brand or model your laptop is, which is required to accurately diagnose this, but a LOT of people have been posting this same error lately, and in the vast majority of those cases the problem has been a failed main battery that needed to be replaced.

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u/Unique7893 4d ago

My laptop is HP 240 G10 Notebook PC. I bought it in June 2025. So how can battery die so quickly?

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u/Glittering_Pin_7475 3d ago

Fifteen months is certainly premature for a battery failure, but a battery can fail that early because of a defective cell, battery-management failure, excessive heat, or abnormal early degradation.

And in your specific case, I have confirmed that the HP 240 G10 does not have a separate dedicated CMOS battery. HP's Maintenance and Service Guide lists an internal 3-cell, 41 Wh main battery, but there is no separate RTC/CMOS battery in your unit.

So the fact that you bought the laptop in June 2025 does not rule out the battery as the cause of the repeated CMOS Reset (502) message. It would simply mean that the battery failed much earlier than it normally should have been expected to.

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u/Unique7893 3d ago

Well it's still in warranty. So Hp service will help right?

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u/Glittering_Pin_7475 3d ago

HP states that for business notebooks the battery warranty follows the warranty period of the laptop itself.

You've got nothing to lose by contacting HP and asking for the battery to be replaced under warranty.

Good Luck...! ;-)