CMOS checksum error, CMOS Reset (502) after battery replacement

[jo1612]

Hi all,

after replacing my main battery my notebook only starts once hooked to ac power. Otherwise it wont even turn on. Once it showes a cmos checksum error for a few seconds, it boots normally. After resetting cmos, the notebook runs normally and I can unplug ac power. I think the battery replacement somhow corrupted my bios. I think my model does not have a cmos battery.

I already updated to the latest bios version and resetted cmos a couple of times. Unfortunately, it did not help. Any advice what to do and why this happens? After looking on the internet, I am not the only one having this kind of problem after a battery replacement, but I couldn't find any helpful solution.

Happy about any advice :-).

Best,

jo1612

[itsmyname]

@jo1612 --  it shows a CMOS checksum error for a few seconds ... I think my model does not have a CMOS battery.

I think that it does, and that the CMOS battery has achieved its "end-of-life" status.

Get a computer technician to disassemble the laptop, to look for the CMOS battery, and to replace it.

Or, read the advice given on REDDIT, for a similar problem:  CMOS checksum invalid, HP 15-da0347ng : techsupport (reddit.com)

How old is your computer?

[jo1612]

I find it odd that this problem occurs right after replacing the main battery... I cannot find any post where somebody tried replacing a cmos battery of this model. The reddit post is mine as well 🙂

I bought the notebook in 2019 and used it nearly every day

[itsmyname]

@jo1612 --  I find it odd that this problem occurs right after replacing the main battery... 

That probably is the first time that you ever removed the main battery from the computer.

The main battery  could have been providing a "trickle" of charge to the CMOS battery, to keep it working.

When you removed the battery, the "deadness" of the CMOS battery became noticeable. 

>  I cannot find any post where somebody tried replacing a CMOS battery of this model.

I cannot find any creditable picture on the Internet of anyone being hijacked into an alien spacecraft that was hiding in the tail of the Hale-Bopp comet. But, of course, some people will say that it has happened to them.  Finding nothing could mean that you have not done enough searching.

> The reddit post is mine as well 

Did you also write the responses to it? Did you try any of those responses?

I think that It is rare for a CMOS battery that was "new" in 2019 to fail in 2021. But, it can happen.

A Google-search for: how long does a cmos battery last in a laptop

suggests that a CMOS battery lasts for 2 to 10 years, but lasts longer when the laptop is receiving power (battery or power-adapter).

[jo1612]

As far as I know does the main battery also serve as the cmos battery. See a similar model with the same problem in the post blow.

https://h30434.www3.hp.com/t5/Notebook-Hardware-and-Upgrade-Questions/Where-is-the-cmos-battery-or-r...

[itsmyname]

@jo1612 -- As far as I know does the main battery also serve as the CMOS battery.

I strongly disagree.  Don't believe everything you read on the Internet.

Here is my experience.

I have two "main" functional batteries for my laptop. 

When I am travelling (long bus or train or ferry trip), there is no opportunity to use the laptop's charger.

So, I use one battery, until its charge runs down.

Then, I hibernate the laptop, swap to the other (fully-charged) battery, "wake" the laptop, and continue to use it.

I never get a "CMOS Checksum Error", because the laptop's "healthy"  CMOS battery continues to supply "trickle" power to the CMOS. Thus, the CMOS settings, including date/time, remain unaffected.

Face it -- your CMOS battery is "on life-support", and only "non-stop" power has kept it "alive". The minute that you disconnect the AC power, and also remove the battery, your CMOS battery lacks enough charge to continually "trickle" power to the CMOS, and you lose the CMOS settings, and that triggers the "CMOS Checksum Error".

[jo1612]

Okay, I'll try looking for the cmos battery then. Thank you so much for your help 🙂

[itsmyname]

@jo1612 -- the CMOS battery may possibly NOT be a FRU (Field Replaceable Unit) -- it might be integrated into the motherboard. A friend who is a "board-level" repair technician has, in the past, soldered-in a new battery, in "parallel" with the existing battery. I don't remember if it was a HP motherboard, or some other company's motherboard.