But he didnt say that the battery was even opened or cells replaced thats why i didnt mention it

 Sometimes same behavior could be observed even on genuine never-opened battery after some usage period, when cells impedances are increasing and CEDV points are shifted and so does not aligned with what is preprogrammed.

Posted by: @antonio

after full charge the discharge is normal till 50-40% and then it suddenly drops down to 5-6%.

...

Forcing a restart, the laptop with such 'depleted' battery will continue to work normally for for 2-3 more hours

  This is typical scenario when chemistry profile in the battery management chip does not correspond to the actual chemistry curves of the cells. It could not be easily resolved. It first need to determine which cells used in the battery and which chip. Are they genuine or copy.

Then try to load appropriate chemistry profile into chip and to run some cycles to check discharge curves.

Yes you are absolutely right and i agree this is a  typical problem if you replace cells with different chemistry  the EDV levels will not be right.  But he didnt say that the battery was even opened or cells replaced thats why i didnt mention it. But this was my first guess.

Here is the 'strange' behavior of the battery integrated inside a Latitude laptop: after full charge the discharge is normal till 50-40% and then it suddenly drops down to 5-6%. After few minutes the device goes into suspended mode because of the critical battery level. Forcing a restart, the laptop with such 'depleted' battery will continue to work normally for for 2-3 more hours. This makes me clear the battery capacity is there (5-6 hours is a good performance for a used battery) but the HW/SW is not correctly detecting it. Any attempt to reset the battery management (Dell recommendations) has failed. Attached are the charge-discharge data collected both under BIOS and under W10. Has this issue been seen by someone in the Forum and maybe resolved with the help of the Battery Analyzer?

Where are you from Antonio ? Maybe you can send the battery to Romania for a free check.

As the other colleagues recommended, it is important to have a look a dynamic parameters and to see how discharge cell voltage curves look like.

after full charge the discharge is normal till 50-40% and then it suddenly drops down to 5-6%.

...

Forcing a restart, the laptop with such 'depleted' battery will continue to work normally for for 2-3 more hours

  This is typical scenario when chemistry profile in the battery management chip does not correspond to the actual chemistry curves of the cells. It could not be easily resolved. It first need to determine which cells used in the battery and which chip. Are they genuine or copy.

Then try to load appropriate chemistry profile into chip and to run some cycles to check discharge curves.