Where is the cmos battery on a 5420
where do i find the cmos batterry on a dell latitude 5420 made in 2021?
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Hi @paul97014
There is no separate RTC (Real Time Clock aka cmos) battery in the laptop.
The RTC function is provided by a power feed taken from the battery in the laptop.
If you wish to perform a power refresh to reset the BIOS in case it is corrupted, preventing a normal start etc, then you will have to disconnect the main battery from the motherboard for a while or press the Power button for 30 seconds after the battery is disconnected to dissipate any residual power from the motherboard.
Here's the owner manual. Go to p.33 to view the procedure to remove/replace the battery/battery cable.
Note: A power refresh will not reset the the HDD password (if set in BIOS) or the BIOS password. It will only restore the other user definable BIOS settings to their factory default settings.
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how do I reset the bios password then?
Unless you can find a hack online (I can't) you either need to replace the BIOS IC, reprogram it or contact the manufacturer.
This was introduced a long time ago as security measure against theft for resale etc
ok. how do i replace the bios ic?
You have to find it on the motherboard, and use smd soldering techniques and tools to unsolder it - not easy as there's a lot of closely packed pins on the IC chip and then find a pre programmed for the motherboard same IC and solder it in its place or find the same IC (model number printed on IC), and programme it with the correct software for the motherboard (not just what's available as an update online from Lenovo) i.e a BIOS.bin file using a programming tool and then solder it onto the motherboard and then check if it works.
Definitely not worth doing if you've never done it before and haven't got the right tools etc - probably cause damage rendering the motherboard unusable. May as well get a new motherboard instead.
If you are the original owner of the laptop, contacting the manufacturer is the best option although it still may cost you.
If it is a 2nd hand (used) laptop, contact the seller and ask them for the password info if they have it.
