problems after battery replacement

[Henk1959]

battery is replaced, after that a mwssage cmos reset 502 and a black screen. how can i fix this

[Hawks_Eye]

Hi @Henk1959 

Welcome to the HP Support Community! We're here to help you get back up and running.

Thanks for sharing the situation—I'm really sorry you're facing this after replacing the battery. A CMOS Reset (502) message followed by a black screen typically means the system detected a BIOS configuration loss and is unable to proceed with normal startup. 

Let’s walk through a focused recovery path to bring your system back to life.

 

Step-by-step actions to resolve CMOS Reset 502 and black screen

1. Perform a full power reset
This clears residual charge and resets embedded controller states:

• Disconnect the power adapter
• If the battery is removable, take it out
• Press and hold the power button for 30 seconds
• Reconnect the battery and adapter
• Power on the system

2. Reset BIOS using key combination
If the screen remains black:

• With the laptop off, press and hold Win + B
• While holding those keys, press and hold the power button for 2–3 seconds, then release the power button but keep holding Win + B for another 10–15 seconds
• If successful, the system will beep or flash and attempt BIOS recovery
• Wait for the recovery screen to appear

3. Re-seat or recheck the CMOS battery (if accessible)
If you replaced a coin-cell CMOS battery:

• Power off and unplug the system
• Remove the CMOS battery for 5 minutes
• Reinsert it firmly and ensure polarity is correct
• Power on again

4. Attempt to enter BIOS manually
If the screen shows the CMOS Reset 502 message briefly:

• Press F10 repeatedly at startup to enter BIOS
• Once inside, go to Exit > Load Setup Defaults
• Save and exit

5. Reflash BIOS (if system remains unresponsive)
If the system doesn’t display anything:

• Use another PC to download the latest BIOS for your model from HP’s support site
• Create a BIOS recovery USB using the HP BIOS utility
• Insert the USB into the affected system
• Use the Win + B method again to trigger recovery

You can find the BIOS for your model here: HP Software and Driver Downloads

You're doing the right thing by addressing this early, and I’ll guide you through the next steps if needed.

If my response helped, please mark it as an Accepted Solution! ✅ It helps others and spreads support. 💙 Also, tapping "Yes" on "Was this reply helpful?" makes a big difference! Thanks! 😊

Take care, and have an amazing day!

Regards, 

Hawks_Eye