How to identify the CMOS battery needed for my laptop?

JohnB47

I've found a video showing disassembly of my actual model of laptop - Toshiba Sattelite L50-C-1XP and I can see that the CMOS battery is easy to replace. My laptop was purchased in 2016. As I will be replacing the hard drive (with a SSD), would it be sensible to replace the CMOS battery at the same time? It isn't giving me any problems to date. If I do decide to change it - how do I find out which type to replace it with? I've searched the internet and I can't get any information. I can see sites that sell wired type but not button type - which is what my laptop has. Also, I'm planning to do a software reset the BIOS at the same time as replacing the hard drive - will removing and replacing the battery upset that process - or will it simply duplicate it? Thanks.

[Deleted User]

Almost certainly a CR2032 battery. The current battery should show a type number on it to be sure. I recommend you whip the lid off before ordering one just to check. Some laptops no longer use a CMOS battery.

BIOS will settings will usually reset to factory default when removing the battery but perform a manual reset anyway after fitting the new battery if you are doing it anyway.

You can of course swap the battery whilst powered up to avoid losing the settings but this isn't needed in your case.

JohnB47

Deleted_User said:

Almost certainly a CR2032 battery. The current battery should show a type number on it to be sure. I recommend you whip the lid off before ordering one just to check. Some laptops no longer use a CMOS battery.

BIOS will settings will usually reset to factory default when removing the battery but perform a manual reset anyway after fitting the new battery if you are doing it anyway.

You can of course swap the battery whilst powered up to avoid losing the settings but this isn't needed in your case.

Thanks. I seem to remember reading that the battery was kept charged, that's why I though it would be something special. But a CR2032 is just lithium and can't be charged. Perhaps I mis-read. I actually have some CR2032s, so perhaps I could go ahead and replace it while there.

Neil_Jones

JohnB47 said:

Deleted_User said:

Almost certainly a CR2032 battery. The current battery should show a type number on it to be sure. I recommend you whip the lid off before ordering one just to check. Some laptops no longer use a CMOS battery.

BIOS will settings will usually reset to factory default when removing the battery but perform a manual reset anyway after fitting the new battery if you are doing it anyway.

You can of course swap the battery whilst powered up to avoid losing the settings but this isn't needed in your case.

Thanks. I seem to remember reading that the battery was kept charged, that's why I though it would be something special. But a CR2032 is just lithium and can't be charged. Perhaps I mis-read. I actually have some CR2032s, so perhaps I could go ahead and replace it while there.

Technically speaking the CMOS battery just helps retain certain settings when its off power for a substantial period of time - that's its only real job, otherwise it would forget about certain setups and what the date/time is (the former isn't so important in most laptops) so it wouldn't boot.  The boards are designed in such a way that if power is pulled from the system the power from the battery takes over.  CR2032 rechargeable batteries do exist, but they'll be "dumb" as the battery is not intended to be charged, so once the charge goes from a rechargeable battery it would still have to be changed 3/5/7/10 years down the line in any event.

What you're probably thinking of is providing power to the key area.  If the device is plugged in (assuming a desktop), the PSU will supply 5V standby power to the motherboard to keep CMOS memory energized while the system is off.  How this is implemented on a laptop may vary, but its probably safe to assume the main battery does the same job.